4.1 Notes and References for Part 1

CHAPTER 1.1 THEORETICAL MODEL TO EXPLAIN THE DOUGHMAKING PROCESS and CHAPTER 1.2 APPLICATION OF FUNDAMENTAL DOUGH-MIXING PARAMETERS

Tschernych, W. Ja., Putschkowa, I. J., Ljaskowskij, D. I., Salapin, M. B., and Tscheuschner, H.-D. (1985) Investigations concerning the influence of mixing-intensity and mixing-time during the discontinuous preparation of wheat-flour dough (German). Collaborative research USSR/GDR. Backer und Konditor, 1, p .. 22-4 (VEB-Fachbuchverlag, Leipzig, GDR). Fig. 1 Dough viscosity versus mixing-time at various mixer-rpm. Fig. 2 Specific mixing-intensity versus mixing-time. Fig. 3 Specific mixing-intensity versus mixing-time at various rpm. Fig. 4 Specific energy input versus mixing-time at various rpm. Stear, C. A. (1986) Dynamics of the discontinuous mixing process and its rationalization. Getreide Mehl und Brot, 40(10), p.294-7. Fig. 5 Dough viscosity versus mixing-time at various rpm. Fig. 6 Mixing torque versus mixing-time at various rpm. Fig. 7 Specific mixing-intensity versus mixing-time at various rpm. Fig. 8 Specific energy input versus mixing-time at various rpm.

CHAPTER 1.3 FUNDAMENTAL CONSIDERATIONS CONCERNING DOUGH RHEOLOGICAL ELEMENTS AND DYNAMIC MIXING PARAMETERS

Halton, P., and Scott-Blair, G. W. (1936-1937). J. Physical Chemistry, XI, p. 561, 1936. J. Physical Chemistry, XI, p. 811, 1936. Cereal Chemistry, XIV, p. 201, 1937 (English). Lerchental, C. H., and Muller, H. G. (1967) Research in dough rheology at the Israel Institute of Technology. Cereal Science Today, 12(5), p. 185-92 (English). Hlynka, I., and Anderson, J. A. (1952) Relaxation of tension in stretched dough. Canadian Journal Technology, 30, p. 198 (English). Dempster, C. J., Hlynka, I., and Anderson, J. A. (1953) Cereal Chemistry, 30, p. 492 (English). Frazier, P. J., Brimblecombe, F. A., Daniels, N. W. R., and Russell-Eggitt, P. W. (1979) Better bread from weaker wheats-rheological considerations. Getreide Mehlund Brot, 33, 10, p. 268-71 (German). Fig. 3 Comparison of rheological data and baking quality of mechanically developed doughs. Lutsishina, E. G., and Matyash, A. I. (1984) Deposited Doc. 1984 VINITI 3547-84 10 pp. (Russian). 721 722 Handbook of breadmaking technology (jrsi, F., Pallagi-Biinkfalvi, E., and Lastity, R. (1985) Analysis of the correlation between flour quality and electrophoretic protein spectra. Acta Alimentaria, 14, 1, p. 49-57 (German). Kawamura, E. G. and co-workers (1985) Selective reduction of inter-polypeptide and intra• polypeptide SS-bonds of wheat glutenin from defatted flour. Cereal Chemistry, 62, p. 279-83 (English). Moonen, J. H. E., Scheepstra, A., and Graveland, A. (1985) Biochemical properties of some high molar weight sub-units of glutenins. Journal of Cereal Science, 3(1), p. 17-27 (English).

CHAPTER 1.4 WATER-BINDING CAPACITY OF DOUGH COMPONENTS AND DOUGH CONSISTENCY CONTROL

Jazuba, W. I., Siderowa, o. G., Putschkowa, L. I., and Tscheuschner, H.-D. (1985) Influence of mixing-intensity and mixing-time on the water-binding capacity of the components of wheat flour dough. Backer und Konditor, 3, p. 90-2 (VEB-Fachbuchverlag, Leipzig, GDR) (German). Collaborative research USSR/GDR. Baker, J., Parker, H., and Mize, M. (1946) Supercentrifugates from dough. Cereal Chemistry, 1, p. 16. Auerman, L. Ja. (1972) Breadmaking Technology, 7th edn, Food Industry Publishers, Moscow, USSR, 1972, p. 511 (Russian). Kosmina, N. P. (1978) Biochemistry of Breadmaking, Food Industry Publishers, Moscow, USSR, 1978, p. 277 (Russian). Table 1 Distribution of moisture in the dough components, Jazuba, W. I., Siderowa, O. G., Putschkowa, L. I., and Tscheuschner, H.-D. Backer und Konditor, 3, 1985, p. 92. Table 2 Analysis of the dough fractions after ultracentrifugation, Jazuba, W. I., Siderowa, O. G., Putschkowa, L. I., and Tscheuschner, H.-D. Backer und Konditor, 3, 1985, p. 92. (Collaborative research USSR/GDR.)

CHAPTER 1.5 EFFECTS OF DOUGH ADDITIVES

Marston, P. E. (1971) Bakers Digest, December issue, p. 16-19 and 62. Chemical activation of dough development under slow mixing conditions. (Australian Bread Research Institute, N. Ryde, NSW, Australia.) Henika, R. G., and Rogers, N. E. U.S. Patent 3,053,666 Sept. 11, 1962. Foremost Dairies, Inc., Dublin, California, USA. Allen, W. G., and Spradlin, J. E. (1974) Properties of commercial amylases for bakery applications. Bakers Digest, 48(3), 14. Reference source 1985, Proteolytic activity of malt and fungal enzymes supplements. Bakers Digest, Kansas 66201, USA. Pfeilsticker, K., and Marx, F. (1986) Gas-chromatographic and Mass-spectrographic studies on the redox reaction kinetics of L-ascorbic acid and L-dehydro-ascorbic acid in wheat-flour doughs. Rheinischen Friedrich-Wilhelms University, Bonn, FRG. Z. Lebensmittel Untersuchung und Forschung, 182(3), p.191-5 (German). Vangelov, A., Naidenova, R., and Karadzhov, G. (1985) Comparative evaluation of the effect of ascorbic acid and iso-ascorbic acid on bread quality. Higher Technological Institute for the Food Industry, Plovdiv, Bulgaria. Nauchui Tr- Vissh. Khranit. Vkusova Prom.-st, Plovdiv, 32(1), p. 133-40 (Bulgarian). Kuninori, T., and Matsumoto, /I. (1963) L-Ascorbic acid oxidizing system in dough and dough improvement. Cereal Chemistry, 40, p. 647-57. Notes and references 723

Prihoda, J., Hampl, J., and Holas, J. (1971) Effects of ascorbic acid and potassium bromate on the viscous properties of dough measured with a Hoppler-consistometer. Chemical and Technological University, Prague, Czechoslovakia. Cereal Chemistry, 48, 1, p. 68-74. Giacanelli, E. (1972) Mechanical and chemical development of bread doughs III. Ind. Alimentari, 11(5), p. 93-8. Jorgensen, H. (1935) Contribution to the explanation of the inhibitory effect of oxidants on proteolytic enzyme activity: the nature of the effect of potassium bromate and similar substances on the baking properties of wheat-flour. Biochemische Zeitschrift, 280, p. 1-37 and 283, p. 134-145 (German). Jorgensen, H. (1935) Nature of the bromate-effect. Miihlenlaboratorium, 5, p. 113-125. Jorgensen, H. (1939) Further investigations into the nature of the action of bromates and ascorbic acid on the baking strength of wheat-flour. Cereal Chemistry, 16, p. 51-60. Elion, E. (1945) The role of proteolysis in bread dough. Bakers Digest, April issue, p. 15-17 and 27-28. Coventry, D. R., Carnegie, P. R. and Jones, I. K. (1972) The total glutathione content of flour and its relation to the rheological properties of dough. J. Sci. Food Agric., 23, p. 587-94. Karpenko, V. I. (1985) Relation of dough properties and bread quality to the separation of glutathione from yeast. Khlebopek. Konditer Prom-st, 9, p. 40-2. Voronezh. Tekhnol. Inst., Voronezh, USSR (Russian). Grunert, S., Mohr, B., and Kroll, J. (1986) Model techniques for investigation of the interaction between proteins and emulsifiers. Lebensmittelindustrie, 1, p. 17-20 (German). Lucny, M. Wheat and rye/wheat products with the addition of monoacylglycerol diacetyltartrate. Czech patent, CS 210,528, 15 July 1983 (Czech). Kawka, A., and Gasiorowski, H. (1985) Effect of sodium stearoyl-2-lactylate on the overall quality of wheat/rye mixed bread (1: 1), enriched with skimmed milk powder. Getreide Mehl und Brot, 39, 12, p. 369-73. Institute of Food Technology, Agric. University, Poznan, PL- 60624, Poznan, Poland (German). Moore, W. R., and Hoseney, R. C. (1986) Influence of shortening and surfactants on retention of carbon dioxide in bread doughs. Cereal Chemistry, 63,2, p. 67-70. Kansas State University, Manhatten, Kansas, USA. Ofelt, C. W., and Smith, A. K. (1954) Baking behavior and oxidation requirements of soy-flour. I. Commercial full-fat soy-flours. II. Commercial defatted soy-flours. Cereal Chemistry, 31(1), p. 15-22. Pollock, J. M., and Geddes, W. F. (1960) Soy-flour as a white-bread ingredient. I. Preparation of raw and heat-treated soy-flours, and their effects on dough and bread. II. Fractionation of raw soy-flour and effects ofthe fractions in bread. Cereal Chemistry, 37(1), p. 19-29 and 30-54. J. Rank Limited, partly in collaboration with J. G. Hay. British patents: 646311, 706942, 771361, 880182. French patent: 1,070174. Methods for the improvement of the baking properties and crumb color of bread by high-speed, or 2-7 times extended mixing-time. Daniels, N. w., Frazier, P. J., and Wood, P. S. (1971) Flour lipids and dough development. Bakers Digest, August issue, p. 20-26. Pashchenko, L. P., Mazur, P. Ya., Serbulov, Yu. S., and Zolotykh, I. N. (1984) Dependence of the rheological properties of liquid semi-products on a surfactant and oxygen. Khlebopek. Konditor Prom-st, 11, p. 24-7 (Russian). Model of a phospholipid (lecithin) molecule. Kleine Enzyklopiidie-Natur (1971) p. 189. VEB• Bibliographisches Institut, Leipzig, GDR (German). Sullivan, B. (1954) Proteins in flour-Review of the physical characteristics of gluten and reactive-groups involved in changes in oxidation. J. Agr. Food Chern., 2, 1231-4. 724 Handbook of breadmaking technology

Grosskreutz, J. C. (1960) The physical structure of wheat protein. Biochim. biophys. Acta., 38, 400-9. A lipoprotein model of wheat gluten structure. Cereal Chem., 38 336-49. Hess, K. Zwickel-und Haftprotein (Wedge and Adherent Protein) Kolloid z., 136 (1954) 84. Kolloid Z. 141 (1955) 61. Rohrlich, M. and Milller, K. (1968) Investigations concerning the FatjProtein Complex in Cereals. Die Milhlle, 41. Kyowa Hakko Kogo Co Ltd (Patent) Euro. Patent Appl. 134,658 March 20, 1985. 'Improvement of Performance of Vital Wheat Gluten'. Schematic diagrams Fig. 15 Amino acids in Wheat Gluten protein (Dimler). Fig. 16 Model of gluten-sheet showing double-layer of Phospholipid in the Lipoprotein slip• plane (Grosskreutz). Stepanova, O. N. and Akimova, A. A. (1986) (Russ) Khlebopek, Konditer Prom-st, 2, 32-4. Farrand, E. A. (1969) Starch damage and alpha-amylase as a basis for mathematical models relating to flour water absorption. Cereal Chem., 46, March issue, p. 103-16. Schulz, A. (1962 and 1963) The influence of starch-degrading enzymes of rye and wheat of the chloride ion. Brot und Rebiick, 16, 8, p. 101-43, 1962 (German). The salt-effect during the processing of sprouted rye-flours. Brot und Gebiick, 17, 6, p. 112, 1963 (German). Stephan, H. and Schulz, A. (1960 and 1961) Investigations concerning an expedient processing of sprouted rye flours. Brot und Gebiick, 14, 12, p. 240-5, 1960 (German). A contribution to the processing of sprout-damaged flours. Brot und Gebiick, 15, 8, p.162-5, 1961 (German). Huber, H. (1961, 1962 and 1964) Influence of acid and salt on the baking properties of rye flour. Industriebackmeister, 9, No.4, August issue, 1961 (German). Influence of acid and salt on the baking properties of rye flour. Brot und Gebiick, 16, 5, p. 88-95, 1962 (German). The salt-effect during the processing of wheat and rye flour. Brot und Gebiick, February issue, 1964 (German). Mecham, D. K., and Weinstein, N. E. (1952) Lipid-binding in doughs--effects of dough ingredients. Cereal Chem., 29, 6, p. 448-55. Fullerton, J. G. (1969) Lipid-protein interaction. Bakers Digest, December issue, 1969.

CHAPTER 1.6 CHEMICAL BONDING DURING DOUGHMAKING

Laignelet, B., and Dumas, C. (1984) Lipid oxidation and distribution of oxidized lipids during the mixing process of bread flour wheat. Lebens. Wissenschaft und Technologie, 17, 4, p. 226-30. Jackson, G. M. (1983) The effect of endogenous phenolic acids on the rheology of wheat flour doughs. Dissertation Abstracts International, 1983, B 44, No.5, 1439 B. Kolesov, v. M. (1951) The amino-nitrogen content of grain-prolamines. Biochimja, 16, p. 346-9 (Russian). Reznichenko, M. S. (1951) The length of the polypeptide-chains in gliadin. Biochimija, 16, p. 579-83 (Russian). Ewart, J. (1985) Blocked thiols in glutenin and protein quality. J. Sci. Food Agric., 36, 2, p. 101-12. Hess, K. (1954) Protein, gluten and lipoid in wheat grain and flour. Kolloid-Z., 136, 2/3, p.84-99 (German). Noles and references 725

Traub, w., et al. (1957) X-ray studies of the wheat protein complex. Nature (London), 179, p. 769-70. Grosskreutz, J. C. (1961) A lipoprotein model of wheat gluten structure. Cereal Chem., 38, 4, p. 336-49. Vercouteren, R., and Lon tie, R. (1954) The solubilization of the gluten of wheat using dimethyl formamide. Arch. Intern. Physiol., 62, p. 579-80 (French). Bloksma, A. H. (1958) The significance ofthiol- and disulfide-groups in gluten for the baking properties. Getreide und Mehl, 8, 6, p. 65-9 (German). Bushuk, W. (1961) Accessible sulfhydryl-groups in dough. Cereal Chem., 38, 5, p. 438-48. Axford, D. W. E., et al. (1962) Disulfide groups in flour proteins. J. Sci. Food Agric., 13,2,5, p. 177-181. Agatova, A. I., and Proskurjakov, N. I. (1962) Sulfhydryl and disulfide bonds in flour proteins. Biochimija, 27, 1, p. 88-93 (Russian). Lee, C. c., and Samuels, E. R. (1962) A radiochemical method for the estimation of sulfhydryl/disulfide ratio in wheat gluten. Can. J. Chem., 40, 5, p.l040-2. Lutsishina, E. G., and Matyash, A. I. (1984) Wide-band proton NMR-spectrographic study of gluten proteins of wheat. Deposited Doc. 1984 VINITI 3547-84, 10 pp. (Russian). Ponte, J. G. Jr. (1968) Modification of dough properties by organic solvents. Cereal Sci. Today, 13, 10, p. 364-94. Popineau, Y. (1985) Fractionation of acetic acid soluble proteins from wheat gluten by hydrophobic interaction chromatography; evidence for different behaviour of gliadin and glutenin proteins. J. Cereal Sci., 3, 1, p. 29-38. Zawistoll'ska, U., and Bushuk, W (1986) Electrophoretic characterization of a low molecular weight wheat protein of variable solubility. J. Sci. Food and Agric., 37, 4, p. 409-17. Ma Ching Yung, Oomah B. Dave, and Holme, John (1986) Effect of deamination and succinylation on some physicochemical and baking properties of gluten. J. Food Sci., 51, 1, p. 99-103. Bushuk, w., Bekes, F., McMaster, G. J., and Zawistowska, U. (1985) Carbohydrate and lipid complexes with protein in gluten. Veroff. Arbeitsgem. Geteideforsch., 1985, 198,3-9 (German). (Berliner Tag. Getreidechem., 35, 1984.) Wall, J. S. Review of wheat protein; Bietz, J. A., Huebner, F. R., and Wall, J. S. Schematic of configuration differences between gliadin and glutenin and the hydrated visco-elastic structures which form gluten. Bakers Digest, 47, 1,26, 1973. Schematics of complex interactions during breadmaking. (A) Starch-lipid-protein complex of flour, according to Hess, K. (B) Phospholipid-protein bonding. (C) Lipoprotein model, according to Grosskreutz, J. C. (D) Gliadin-glutolipid-glutenin complex, according to Hoseney, R. C. et al. (E) Starch-glycolipid-gluten complex, according to Wehrli, H. P. Hoseney, R. c., Finney, K. F., Pomeranz, Y. (1970) Functional (breadmaking) and biochemical properties of wheat flour components VI. Gliadin-lipid-glutenin interaction in wheat gluten. Cereal Chern., 47, 2, p. 135-9. Wehrli, H. P., and Pomeranz, Y. (1970) A note on the interaction between glycolipids and wheat flour macromolecules. Cereal Chern., 47, 2, p. 160-6. . Pomeranz, Y. (1985) Wheat flour lipids-what they can and cannot do in bread. Cereal Foods World, 30, 7, p. 443-6. Mac Ritchie, F. (1985) Studies of the methodology for fractionation and reconstruction of wheat flours. J. Cereal Sci., 3, 3, p. 221-30. 726 Handbook of breadmaking technology

Pallagi-Biinkfalvi, E. (1983) Analysis by polyacrylamide-gel electrophoresis (PAGE) of proteins in wheat flours and doughs. Acta Alimentaria, 12, 1983 (English). Bogdanov, V. P., et al. (1985) Difference in polypeptide composition of glutenins from wheats with different baking qualities. Prikl. Biokhim. Mikrobiol., 21, 6, p. 838-42 (Russian). Graveland, A. et al. (1985) A model of the molecular structure of glutenins from wheat flour. J. Cereal Sci., 3, 1, p. 1-16. Hoseney, R. C. et al. (1970) Cereal Chem., 47, 2, p. 135-139. Daniels, N. w., et al. (1971) Flour lipids and dough development. Bakers Digest, August issue, p.20--6. Wehrli, H. P., and Pomeranz, Y. (1970) Cereal Chem. 47, 2, p. 160--6. Tortosa, E., et al. (1985) Chemical changes during bread dough fermentation I. Lipids of bread dough. Rev. Agroquim. Tecnol. Aliment., 25, 3, p. 417-27 (Spanish). Ma Ching Yung, Oomah B. Dave, and Holme John (1986) J. Food Sci., 51, I, p. 99-103. Woychik, J. H., Boundy, J. A., and Dimler, R. J. (1961) Hydrophobicities of gliadin and glutenin. J. Agr. Food Chem., 9, 4, p. 307-10 (under title: 'Amino acid composition of proteins in wheat flour'). Cluskey, J. E., and Wu, Y. V. (1966) Structure of gliadin and glutenin. Cereal Chem., 43, p. 119. Lenard, J., and Sing,er, J. S. (1966) Alpha-helices stabilization by hydrophobic amino acids. Proc. Nat. A cad. Sci. USA, 56, p. 1828.

Vakar, A. B. et at. (1985) Influence of D 20 on the physical properties of gluten and wheat dough. Prikl. Biokhim. Mikrobiol., 1, p. 5-24 (Russian). Bloksma, A. H. (1975) Cereal Chem., 52 (3, Part II). 170r. Ewart, J. A. D. (1977) J. Sci. Food Agric., 28, p. 191. Ewart, J. A. D. (1978) J. Sci. Food Agric., 21, p. 551. Ewart, J. A. D. (1985) Blocked thiols in glutenin, and protein quality. J. Sci. Food Agric., 36, 2, p. 101-12. Tsen, C. c., and Bushuk, W. (1963) Dough mixing in air vs. in nitrogen. Cereal Chem., 40, p. 399-408 (under title: Changes in SH and SS contents of doughs during mixing under various conditions). . Sullivan, B., et al. (1963) The oxidation of wheat flour-labile and non-labile SH groups. Cereal Chem., 40, 5, p. 515-31. Mamarit, F. P., and Pomeranz, Y. (1966) The isolation and characterization of wheat flour proteins. IV. Effects on wheat flour proteins of dough mixing and of oxidizing agents. J. Sci. Food Agric., 17, p. 339-43. Hguyen-Brem, P. T., et al. (1983) Oxidation/reduction effects on flour proteins-molecular weight distribution. Getreide Mehl und Brot, 37, p. 35 (German). Dirndorfer, M., et al. (1986) Changes in glutens of various wheat varieties by oxidation. Lebensmittel Untersuch. und Forsch., 183, I, p. 33-8 (German). Kosmina, N. P. (1958) Proteins of rye and rye gluten. Getreidemuhle, 2, 6, p. 122-3 (German). Vones, E., et al. (1964) Significance of wedge proteins of rye flour for dough properties. Cereal Chem., 41, p. 456-64. Anger, H., et at. (1986) Molecular weight and limit-viscosity of arabinoxylan (Pentosan) from Notes and references 727

rye (Secale cereale); formulation of the Mark-Honwink relationship. Die Nahrung, 30, 2, p. 205-8 (German). Neukom, H., and Markwalder, M. (1978) Oxidative gelling of wheat flour pentosans-a new possibility of polymeric linkage. Cereal Foods World, 55, 7, p. 374-6. Holas, J., et al. (1973) Grain polysaccharides of the pentosan type VI. Investigation of the protein component of the pentosans and hemicelluloses. Mlynsko-pekarensky prum. Praha, 19, 1, p. 11-14 (Czech.). Kolesov, V. M. (1951) The amino-nitrogen content of grain prolamines. Biochimija, 16, 579-83 (Russian). Perlin, A. S. (1951) Structure of the soluble pentosans of wheat flours. Cereal Chem., 28, 5, p. 382-93. Montgomery, R., and Smith, F. (1955) The carbohydrates of the gramineae V. The con• stitution of a hemicellulose of the endosperm of wheat (Triticum vulgare). J. Am. Chem. Soc., 77, p. 2834-7. Cole, E. W. (1967) Isolation and chromatographic fractionation of hemic ell uloses from wheat flour. Cereal Chem., 44, 4, p. 411-16. Medcalf, D. G., D'Appolonia, B. L., and Gilles, K. A. (1968) Comparison of the chemical composition and properties between HRS and durum wheat endosperm pen to sans. Cereal Chem., 45, 6, p. 539-49. Kosmina, N. P. The Biochemistry of Breadmaking, VEB-Fachbuchverlag, Leipzig, 1977 (German). Holas, J. et al. (1974) Grain polysaccharides of the pentosan type XII. Changes in the pentosan fractions during breadmaking. Mljmsko-pekarensky prum. Praha, 20, 2, p. 46-8 (Czech.). Schmieder, W. (1977) Problems concerning the evaluation of rye for breadmaking from analytical data, with special reference to breeder's sample material. Dissertation, 1977 (German). Drews, E. (1973) Variations in the quality of flour type 997, depending on the properties of the rye grain. Getreide Mehl und Brot, 27, 10, p. 305-311 (German). Drell's, E., and Zwingelberg, H. (1977) Results from many years of rye investigations concerning varieties, location, and crop year with particular reference to flour properties. Getreide MellI und Brot, 33, 2, p. 34-7 (German). Drews, E. (1979) Milling properties as a function of grain properties, and their effect on flour quality. Getreide MellI und Brot, 33, 2, p. 29-34 (German). Meuser, F., et al. (1986) Chemical/physical properties of rye pentosans. Veroff. der Arbeitsgem. fur Getreideforsch. in Berlin, 203, p. 73-89 (German). Kuhn, M. C, and Grosch, W. (1985) The fractionation and reconstruction of rye flour-special technique to study the non-starch polysaccharide hydrolases in rye bread production. Getreide Mehl und Brot, 39, 11, p. 340-344 (German), and in Veroi]: Arbeitsgem. Getreideforsch. Berlin, 1986,203, p. 21-29 (German). Simmonds, H., and Orth, R. A. (1973) Structure and composition of cereal proteins, as related to their potential utilization. In: Industrial Uses of Cereals, Y. Pomeranz, editor, American Association of Cereal Chemists, St Paul, MN, USA. Ewart, J. A. D. (1968) Action of glutaraldehyde, nitrous acid or chlorine on wheat proteins. J. Sci. Food Agric., 19, p. 370. 728 Handbook of breadmaking technology CHAPTER 1.7 TYPICAL FORMULATION AND PROCESS SCHEDULES (INCLUDING CASE STUDIES) FOR WHEAT AND RYE BREADS EMPLOYED IN WESTERN AND EASTERN EUROPE AND NORTH AMERICA

1.7.1 France Calvel, R. (1972) Technical requirements for flours used for bread and baked-products in France. Getreide Mehl und Brot, 26, 3, p. 75-8 (German).

1.7.2 Spain Barber, S., et al. (1983) Microflora of the sour dough of wheat flour bread I. Identification and functional properties of microorganisms of industrial sour doughs. Rev. Agroquim. Tecnol. Aliment., 23, 4, p. 552-62 (Spanish). Laboratorio de Cereales y Proteaginosas, Instituto de Agroquimica y Technologia de Alimentos (CSIC), Valencia 10, Spain. II. Functional properties of commercial yeasts and pure strains of S. cerevisiae in sugar solutions. Rev. Agroquim. Technol. Aliment., 25, 3, 1985, p. 436-46 (Spanish). III. Functional properties of commercial yeasts and pure strains of S. cerevisiae in wheat flour. Rev. Agroquim. Tecnol. Aliment., 25, 4, 1985, p. 447-57 (Spanish). Galli, A., and Ottogalli, G. (1973) Microflora of the sour dough of panettone cake. Annali di Microbiologia ed Enzimologia, 23(1/2/3), p. 39-49 (Italian). Azar, M., et al. (1977) Microbiological aspects ofSangak bread. J. Food Sci. and Technol., 14, 6, p. 251-254.

1.7.5 Federal Republic of Germany (FRG) Quality of the German wheat crop 1986, AGF Detmold, published in Die Miihle und MischJuttertechnik, 1986,42, p. 572-5 (German).

1.7.6 German Democratic Republic (GDR) Quality standards of flours and meals TGL 27424/01. Technology oj Industrial Baking by Schneeweiss, R., and Klose, O. VEB-Fachbuchverlag, Leipzig, 1981, p. 394, Table 66 (German). Special Processes in Baking by Schwate, W., and Ulrich, VEB-Fachbuchverlag, Leipzig, 1986 (German). Authoritative reference for the preparation of special breads. National bread and roB types produced in the GDR, and flour types used to produce them. Adaptation from: Technology oj Industrial Baking by Schneeweiss, R., and Klose, O. Leipzig, 1981, Table 3, p. 21, Definition of Bread Varieties (German). Maschinenlehre Backwaren by B. Schramm, 2nd edn, 1978, VEB-Fachbuchverlag, Leipzig, GDR (German), a machinery handbook for the baking industry recognized by the Food Ministry as suitable for professional education.

1.7.7 USSR Reference sources include: The Technology oj Breadmaking by L. Ja. Auerman, Moscow, 1972 (Russian); German language version published by VEB-Fachbuchverlag, Leipzig, GDR (German), 1977. The Biochemistry oj Breadmaking by N. P. Kosmina, Moscow, 1971 (Russian); German language version published by VEB-Fachbuchverlag, Leipzig, GDR (German), 1977. The Problem ojBaking Properties by Natalie P. Kosmin (Professor of Grain Chemistry at the High School for Milling at Tomsk, USSR), published by Moritz Schafer, Leipzig, GDR. Biochemistry oj Grain and Breadmaking (Biokhimiya zerna i Klebo-pecheniya) by V. L. Kretovich, published by the Academy of Sciences of USSR, 1958. Notes and references 729

Lutsishina, E. G., and Matyash, A. I. (1984) Wide-band proton NMR-spectrographic study of gluten proteins of wheat. Deposited Doc. 1984 VINITI 3447-84, lOpp. (Russian) available from VINITI. Pashchenko, L. P., et al. (1984) Dependence of the rheological properties of liquid semiproducts on a surfactant and oxygen. Khlebopek. Konditer Prom-st, 11, p. 24-7 (Russian). Mazur, P. Ya. (1986) Influence of oxidizers on the change in binding-energy of moisture in flour and dough. Izv. Vyssh. Uchebn. Zaved. Pisheh. Tekhnol., 5, p. 33-7 (Russian). Losa, A. I. (1939) Use ofPFWS soured with L. delbriickii instead of a dough sponge. Bulletin Chlebopekarnaja promyschlennost (WNIIChP publication 1939-1940),4-5,46. Chernaya, L. S., et al. (1986) A biologically-active mixture for improving the quality of wheat bread. Khlebopek. Konditer Prom.-st, 5, p. 28-9 (Russian). Karpenko, V. I. (1986) Relation of dough properties and bread quality to the separation of glutathione from yeast. Khlebopek. Konditer Prom.-st, 9, p. 40-:2 (Russian). Belova, L. D., et al. (1985) Use of starch-syrup to obtain baker's yeast. Khlebopek. Konditer Prom.-st, 4, p. 40-:1 (Russian).

1.7.8 Hungary Case study: The Varpalota Bakery-a modern production unit in the District of Veszprem (Lake Balaton), PRH. Backer und Konditor, 1, 1987, p. 11-12. 1.7.9 Czechoslovakia International Exhibition SALIMA-85 in Brno, Czechoslovakia. Baked-product range, Mixing aggregate T 457,0, Flour feed aggregate T 437'0, as components of the continuous sour-dough and doughmaking plant T 995·0 of Topos, Sluknov, Czechoslovakia. Wire-band tunnel-ovens PPC series of the milling-machinery manufacturers at Pardubice, Czechoslovakia; 3-deck oven type 30 of Merkuria, Czechoslovakia. Complete Doughmaking-lines KVT 1000, 1500 and 1800 for Full-sour to Full-sour production of bread on a continuous basis. Bread-roll lineS't 940 and t 985. Leipzig Fair 1985 (GDR) KVT Type 995·0 for continuous doughmaking line for rye and mixed rye/wheat doughs with outputs 1800 to 25OOkg/h dough, exported by Technopol, Bratislava, Czechoslovakia. Mixer T 457·0 for the KVT doughmaking plant. 1.7.1 0 Poland Case study: Newest and largest bakery and confectionery in Warsaw, Krakowiak Street (near Warsaw Airport). First stage of construction began 1976 for confectionery production, second stage construction of the bakery with six production lines and tunnel-ovens, 2 laboratories, administration and cultural areas, commissioned in 1982. Further construction projects are in hand. Backer und Konditor, 1, 1985, p. 19-21. 1.7.12 United Kingdom (UK) Case study: Two 1950s comparisons of a large multiple-chain London plant bakery, and that of the author's rural family bakery located in a South Devon market town on the coast. Todd, J. P., et al. (1954) Chem. and Industry, 50. Hawthorn, J., and Todd, J. P. (1955) J. Sci. Food Agric., 501. The Blanchard batter process'-no-time dough with less power, article in Milling, 146, p. 520-:21, 1965. 'Blanchard batter, process for bread', article in Milling, 147, p. 519, 1966. 730 Handbook of breadmaking technology

'Process for the improvement of wheat-flour bread', State Committee for Inventions of USSR No. 164860 July 7, 1963. Auerman, L. J., Kretowitsch, W. L., and Polandowa, R. D. Meredith, P. (1966) Combined action of ascorbic acid and potassium bromate as bread dough improvers. Chem. and Industry, p. 948-9. Barret, F. F., and Joiner, R. R. (1967) Dough developer combination ADA and potassium bromate. Bakers Digest, 41, 6, p. 46. Menger, A. (1977) Getreide Mehl und Brot, 31, p. 48. Menger, A. (1978) Getreide Mehl und Brot, 32, p. 13.

1.7.13 North America Kilborn, R. H., and Tipples, K. H. (1968) Sponge-and-dough type bread from mechanically developed doughs. Cereal Sci. Today, 13, 1, p. 25-30. Fermi-tech pre-ferment process, developed by Fermitech Company, Rogers Group Inc., Oberlin, Ohio 44074, USA. Nutrient slurries for pre-ferment systems. Case study: Automatic flour-pre-ferment system at Flowers Baking Company, Miami, Florida, USA. Johnson,J. A. (1974) Precursors of bread flavor. Department of Grain Science, Kansas State University, USA. Proceedings of the 8th National Conference on Wheat Utilization Research at Denver, Colorado, USA. Ponte, J. G. Jr. (1985) Short-time doughs, Bakers Digest (Technical Source), May issue. Freed, R. J. (1963) Continuous dough-developer and extruder. Bakers Digest, 37, 3, p. 55. Kline, L., Sugihara, T. F., and McCready, L. B. (1970) Bakers Digest, 44, p. 48. Nature of the San Francisco sour dough French bread process. I. Mechanics of the process. Bakers Digest, 44, p. 51. II. Microbiological aspects. Sugihara, T. F., Kline, L. and Miller (1971) Microorganisms of the San Francisco sour dough bread process. I. Yeasts responsible for the leavening action. Applied Microbiology, 21, p. 456. II. Isolation and characterization of undescribed bacterial species, responsible for the souring activity. Applied Microbiology, 21, p. 459 (Kline and Sugihara).

CHAPTER 1.8 MEASUREMENT AND CONTROL TECHNIQUES FOR RA W MATERIALS AND PROCESS VARIABLES

Auerman, L. Ja. (1972) Technology of Breadmaking, Moscow; VEB-Fachbuchverlag, Leipzig, 1977 (German), under: Complex parameters which reflect the quantity of gluten and its quality in flour, p. 62-3. Gluten evaluation using the Hpek and Hd Parameters, refer to: The Laboratory Handbookfor Baking Technology by L. I. Putschkova, Moscow, 1971, published by Pistschewaja promyschlennost (Russian), which contains the calculation tables. Wiinsche, R. and Tscheuschner, H.-D. (1984) The cell-structure of wheat-flour dough and the bread-crumb and possibilities for their automatic analysis. Wiss. Zeitschriji der TV Dresden, 33, 3, p. 115-18 (Germany). Bloksma, A. H. (1981) Effect of surface-tension in the gas/dough interface on the rheological behaviour of dough. Cereal Chem., 58, 6, p. 481-6. Notes and references 731

Carlson, T. L.-G., and Bohlin, L. (1978) Free surface energy in the elasticity of wheat-flour dough. Cereal Chem., 55, 4, p. 539-44. Kuzminski}, R. v., Scerbatenko, V. V., and Vassin, M. I. (1977) Dynamics of the cell structure of the bread-crumb. Chlebopek. i kond. prom., 21, 5, p. 21-2. Kuzminski}, R. v., Scerbatenko, V. v., and Vassin, M. I. (1977) Model for the evaluation of bread-crumb cell structure. Chlebopek. i kond. prom., 21, 6, p. 19-20. Zimmermann, R., and Schmidt, S. (1977) The microscopic characteristics of the baked-crumb. Backer und Konditor, 25, 9, p. 262-4 (German). USSR laboratory wheat-flour baking test GOST 9404-60 Standard, paragraph 55-64, Flour and Bran Test Methods: Moscow Isdatelstwo Standard ow, 1963. Laboratory Manual for Technology of Baked Products by Putschkowa, L. I., Moscow, published by Pistschewaja promyschlennost, 1971. AACC standard method for assessment of the baking quality of bread-flour by the sponge• dough pound-loaf method in USA-AACC Method 10-11. Canadian Remix Baking Test, 1960. Irvine, G. N., and McMullan, M. E. Cereal Chem., 37,5, p. 603, 1960. Rye baking-test: sour-dough baking test, Standard Methodsfor Grain Flour and Bread, 4th edn, 1964, p. 151 (German).

Flour Pentosan Determination Cerning, J., and Guilbot, A. (1973) Cereal Chem., 50, p. 176. Petzold, H., and Volkmer, M. (1980) Backer und Konditor, 28, 1980, p. 282.

Yeast Standard test for the baker's yeast industry (proof-time). GDR Standard TGL-25111j03, GDR, May 1971. Jelitzki and Semichatowa: Production-based method for the enzyme-activity of yeast, AII• Union Research for the Baking Industry of USSR.

Bergander, K., and Bahrmann, K. (1957 and 1058) Shelf-life of yeast by electrometric measurement of pH and redox-potential. Nahrung, 1, p. 74, 1957; and Nahrung, 2, p. 500, 1958. Standard Test Method GDR Standard TGL-25111j04 Shelf-life of Baker's Yeast. Josii:, D. (1980) Criteria for the determination of the quality of active dry yeast. Getreide Mehl und Brot, 34, 7, p. 179-81 (German).

Sour-dough Starter Cultures and Sour-dough Stephan, H. (1982) Characteristics of various sour-dough processes and resultant bread quality. Getreide Mehl und Brot, 1, p. 16-19 (German). Schulz, A. (1941) Development and physiological activity of the bacteria and yeasts during the sour-dough stages of whole-rye bread production, and their influence on flavour and quality of the bread. Mehl und Brot, 41, p. 377-9 (German). Fortschrittliche Backerei, 71, Berlin, 1941 (German). Schulz, A. (1954) Zeitschriftfiir das gesamte Getreidewesen, 31, 7-9, p. 51. Gerstenberg, H. (1978) Detection of dough-acidulants in bread from the citric acid content. Z. Lebensmittelchemie und gerichtlichen-chemie, 32, p. 125-6. Rabe, E. (1980 and 1981) Organic acids in breads from various processes. Part I: Methods for the determination of the mode of acidulation. Getreide Mehl und Brot, 34, 4, p. 90-4, 1980. 732 Handbook of breadmaking technology

Part II: Various methods for the determination of the types of acidity. Getreide Mehl und Brot, 6, p. 146--50, 1981. Stephan, H. (1982) Getreide Mehl und Brot, 1, p. 16--19 (German). Pelshenke, P., and Sehulz, A. (1941) Berliner short-sour process. Miihlenlaboratorium, 11, 11, p. 105.

Wheat Sour-dough Barber, s., Baguena, R., Martinez-Anaya, M. A., and Torner, M. J. (1983) The microflora of the sour dough of wheat flour bread. I. Identification and functional properties of microorganisms of industrial Sour-doughs. Rev. Agroquim. Tecnol. Aliment, 23, 4, p. 552--62 (Spanish). Spicher, G., and SeMI/hammer, K. (1977) Comparative investigations concerning the yeasts of pure sour-dough cultures and spontaneous sour-doughs. FSTA, 12, M 1431. Lorenz, K. (1983) Sour-dough processes-methodology and biochemistry. Bakers Digest, 57, 4, p. 41-5. Spicher, G., SchrOder, R., and SeMI/hammer, K. (1979) The microflora of sour-dough VIII. Yeast composition of sour-dough starters. Z. Lebensm. Untersuch. und Forschung, 169, p. 77-81 (German). Spicher, G., and Stephan, H. (1982) Handbook of Sour-dough Biology, Biochemistry and Technology. BBV Wirtschafts-information GmbH, Hamburg (German). Sugihara, F. (1977) Non-traditional fermentation in the production of baked-goods. Bakers Digest, 51, 5, p. 76, 78, 80 and 142. Calvel, R. (1980) Fermentation and processing of natural sour (French). Industries des cereales, No.7 p. 27-35. Industries des cereales, No.5 p. 31-6. Galli, A., and Ottogalli, G. (1973) Fermentation and processing of the sour-dough of panettone cake. Annalidi Microbiologia ed Enzimologia, 23(1,2,3), p. 39-49. Difco Laboratories Inc., Detroit 1, Michigan, USA. Manufacturers of culture media and reagents for microbiological and clinical laboratory procedures. Man, J. C. de, Rogosa, M., and Sharpe, M. E. (1960) A medium for the cultivation of Lactobacilli. J. Appl. Bact., 23, p. 130. Gibson, T., and Abd-el-Malek, Y. (1945) The formation of carbon-dioxide by Lactic acid Bacteria and B. licheniformis, and a cultural method of detecting the process. J. Dairy Research, 14, p. 35. Stamer, J. R., Albury, M. N., and Pederson, C. S. (1964) Substitution of Manganese for Tomato Juice in the Cultivation of Lactic acid bacteria. Applied Microbiology, 12, p. 165. Breed, R. S., Murray, E. G. D., and Smith, N. R. (1957) 'Bergey's Manual of Determinative Bacteriology', 7th Edition, Baltimore: Williams and Wilkins. Gibbs, B. M., and Skinner, F. A. (editors) (1966) 'Identification Methods for Microbiologists', 2 vols. London: Academic Press.

1.8.2 Process Variables /988 Reference Source-A statistical reference manual and specification guide for wholesale baking, published by Sosland Publishing Company, P. O. Box 29155, Shawnee Mission, KS 66201, USA. Temperature Calculation Equations, p. 8. Intensive mixing-aggregate IMK 150, made in the GDR-Winter and Summer dough-water Notes and references 733

temperature adjustments for Wheat and Rye-jlour processing. Machine Manual Baking by B. Schramm, VEB-Fachbuchverlag, Leipzig, GDR (1978), p. 112 (German).

Application of NIR Spectroscopy In-line monitoring of flour-protein, -moisture, -damaged starch, ash, and particle-size, using the Infra Alyzer 250 of Technicon Instruments Corporation, 511 Benedict Ave, Tarrytown, NY 10591-5097. Dough moisture determination at 2045 nanometres within 1 minute, using the GarnerjNeotec 3000 or 7000 units. Gardner Neotec Division, Pacific Scientific, Silver Spring, MD, USA. Final baked-product analysis includes: protein, moisture, fat, sugar, fibre, and SSL levels, using selected wavelengths. TKO plate-dryer for the determination of dough-yield, GDR Standard TGL-29066 (Food Engineering School, Dippoldiswalde, GDR). Nomogram application to relate flour-weight to dough-yield, dough piece yield and baked product yield. Mixing and mixing regimes versus optimization of dough-yield. Efficient use of electric-motors as a power source. Microelectronics, biotechnology and information technology application for process measurement and control systems, leading to CAM and CIM. Data acquisition at each production phase. Fixation of responsibilities, I\"ork-jiol\", and information-flow. Training, and constant updating of qualified personnel. Coordination of problems involving measurement by formation of working-groups, within corporate organizations. In-line monitoring ofdough viscosity and rheology in the oscillatory and relaxation modes, time programmed and computer interfaced. Optical in-line torque transducers can also be applied to measure viscosity; mounted in-line with the drive shaft and mixer element, both speed and torque during dough mixing can be continuously monitored. Measuring systems based on dough deformation in the oscillatory and relaxation modes: System R2 of Rheotec AB, S-22370 Lund, Sweden, for both 'in-line' and 'on-line' measurement of dough rheological deformation in the oscillatory mode, at chosen optimal material response frequencies, within the range 10- 3 to 20Hz. IR-absorption spectroscopy can be applied to the measurement of hydrogen-bonding, monitoring changes taking place during storage of both wheat and flour (maturation), under specified conditions of time, temperature and humidity. Fourier transform infrared (FTl R) spectroscopy, in combination with attenuated total reflectance (ATR) sample presentation, will now allow improved quality spectra from aqueous solutions of food biopolymers, thus overcoming the hitherto limited use of water as an IR solvent, owing to strong band absorption within the range 5000-400 cm - 1. Wilson, R. H., Goodfellow, B. J., and Belton, P. S. (1988) Fourier transform infrared spectroscopy for the study of food biopolymers (includes a complete IR A TR spectrum of bread). Food Hydrocolloids, 2, 2, p. 169~78. McClure, W. F., and Davies, A. M. C. (1987) Fourier self-deconvolution in the analysis ofNIR spectra of chemically complex samples. Mikrochim. Acta, 1(1~6), p. 93~6 (published 1988). Wilson, R. H., and Belton, P. S. (1988) A Fourier transform infrared study of wheat starch gels. Carbohydrate Research, 180, p. 339-44. NI R spectroscopy (reflectance) has also been applied to the measurement of the cold pasting viscosity of extruded starches and flours. The amount of reflected light increases with increasing cold pasting viscosity. Correlations between measured and NIR-reflectance 734 Handbook of breadmaking technology spectra calculated viscosities, from 200 to 1600 mPa s were good, indicating possible process control applications.

Meuser, F., et al. (1987) Application ofNIR spectroscopy for measurement of the viscosity of extruded starch and flours (German). Veroff. Arbeitsgem. Getreideforsch., 208, p. 61-7 (Berliner Tagung fiir Getreidechemie, 37, 1986). N M R instrumental techniques apply powerful magnetic fields from superconducting magnets, which are capable of resolving and identifying minor, but significant structural differences in complex molecules, e.g. polymer composition, chain-branching, tacticity and residual monomer content. High resolution pulsed proton NMR can be used to measure spin-lattice, and spin-spin NMR relaxation-times, thus allowing a determination of free and bound water in materials, and water mobility on storage. Changes in the colloidal state of water with time can be monitored under specific storage conditions, e.g. starch, wheat proteins, and non• starch polysaccharides. The advantage of NMR spectroscopy is that it is a rapid and non• destructive method offood analysis. The most widely applied techniques are based on proton NMR spectroscopy, i.e. water content of foods, solid/liquid ratio of fats and emulsions, lipid-protein exchange reactions in emulsions, monitoring the freezing-processes of various foods. More recently, pulsed NMR spectroscopy has gained in importance for the investigation of food components. Korn, M. (1983) Deutsche Lebensmittelrundschau, 1, p. I (German). Lutsishina, E G., and Matyash, A. I. (1984b) Wide-band proton NMR spectroscopic study of gluten proteins of wheat. Deposited Doc. 1984 VINITI 3547-84, USSR, 10 pp. Available VINITI USSR (Russian). Proton NMR spectroscopy is also being applied to the study of the mechanism of tripeptide glycosylation (glycoproteins), and their conformations. UV spectroscopy has been applied to baking quality determination in Hungary, using 2M urea as a resolution medium for protein, gluten-forming proteins, correlating well with dough water absorption and baking quality. Kovacs, E, and Selmeczy, A. (1985) Application of UV -values in the determination of baking quality. Elelmez. Ipar, 39, 7, p. 272-5 (Hungarian).

Cleanliness and Sanitation (hygiene) American Baking Industry Sanitation Standards Committee (BISSC), represented institutions are: American Bakers Association, Bakery-equipment Manufacturers, American Society of Bakery Engineers, Associated Retailers of America (Bakers), Biscuit and Cracker Manufacturers Association, American Institute of Baking, also Consultants from nationally well-known sanitarians. As a result the FDA publishes lists of equipment and certified manufacturers which meet BISSC standards. Hazard Anall'sis and Critical Control Point Sl'stem (HACCP) concept accepted in USA by the FDA, as accepted procedure for Food Pro~ess Inspection (Denver National Conference of Food Protection, 1971) Issue of 'FDA Compliance Program Guide Manual'. USA concept ol'good manufacturing practices' (G M Ps) FDA Inspectorate in the USA empowered by Congress to examine food producer's quality assurance programs and records to assess daily operations. Federal Food and Cosmetic Act requires the processor to identify control points, and hazards ()f contamination from unsanitary environment, and accept total responsibility legally for its entire programme. Good Manufacturing Practices (GM Ps) Manual is a guideline as to how a food plant is maintained in a clean state. Notes and references 735

Duty offood industry to demonstrate to the public, government and regulatory-agencies that it is producing clean, wholesome and safe foods. Swab test-kits for surface-sanitation, Millipore Corporation, Bedford, MA 01730, USA. UV-liquid sterilizers, PWS Sterilizer Bulletin, available from: Pure Water Systems, 343 Boulevard, Hasbrouck Heights, NJ 07604, USA. Instant spray-nozzle hot/cold water and steam cleaner units, available from: Strahman Valves, Inc., 3 Vreeland Road, Florham Park, NJ 07932, USA. Birco nocorrodefoamer, available from: Birco Chemical Corp., P.O. Box 1315, Denver, CO 80201, USA. Morton Biocidal System includes static and mobile high-pressure washing, cleaning and sanitizing equipment, and in situ production of low pH gaseous chlorine, and sodium hypochlorite from just salt, water and low voltage electricity, available from: Morton Salt Company, Division of Morton Norwich Products Inc., 44 Dock Street, St. Louis, Missouri 63147, USA. Quarternary based combined c1eaner/disinfectant/sanitizer/virucide, marketed by: Robert Langer Co., Inc., USA. Water-activity measurement for prediction of microbial growth support, available from: American Instrument Company, Travenol Laboratories, Inc., Silver Spring, MD 20910, USA. Automatic insect control units, USDA approved, marketed by Virginia Chemicals, Dept 116, Portsmouth, VA 23703, USA. High-pressure/loll'-volume, compact, stationary or mobile, cleaning-station systems, marketed under the 'Economiser' trademark, are available from: Chemidyne Corporation, 8679 Freeway Drive, Macedonia, OH 44056, USA. UHF rodent scarer, operating on compressed air, at low cost, and maintenance-free, is marketed by: Rat-X, 325 W. Huron, Chicago 60610, USA, being international leading rodent-control specialists. Critical Control Point, total-systems approach, considering each unit operation. 'Reference Source', Bakers Digest, 1986, p. 40. Falcon sll"ubes, and Falcon disposable plastic equipment, available from: Falcon Plastics, Division of BioQuest, Baltimore Biological Laboratories, Cockeysville, MD, USA. Atomic Energy Agency, Vienna, responsibile authority for the application of ionizing radiation to food. O.tficial Journal of European Communities No. C99. 13:4 :87 lists current radiation clearances obtained by national governments. UK food irradiation currently based on Food (Control of Irradiation) Regulations Amendment 1972. Baltimore Biological Laboratories ( BBL) culture media for Microbiological studies, available from: BBL, Cockeysville, MD, USA. D(j(-o Laboratories Inc., Detroit 1, Michigan, USA, suppliers of culture media for microbiological studies. Public Health Service Publication, paragraph 729 Fluorescent Antibody Techniques, US Government Printing Office, Washington, D.C., 1960, USA. Spicher, G. (1969) Investigations concerning the occurrence of aflatoxin-forming microflora, and aflatoxin found in bread. Brot und Gebiick, 23, p. 149-52. 736 Handbook of breadmaking technology

Frank, H. K. (1966) Aflatoxins in food Arch. Lebensmittelhyg., 17, p. 237-42 (German). Frank, H. K., and Eyrisch, W. (1968) The detection of aflatoxins, and the occurrence of pseudo• aflatoxins in food. Z. Lebensm. Vnters, Forsch., 138, p. 1-11 (German). Bosenberg, H., and Eberhardt, E. (1969) Studies concerning the contamination of food in supermarkets by moulds. Med. und Erniihrung, 10, p. 12-13 (German). Spicher, G. (1970) Investigations of the occurrence of aflatoxin in bread. Zbl.! Bakt., II, Abt. 124, p. 697-706. Spicher, G. (1984) The toxins of mould growth on baked products, 2nd Part: Mycotoxins occurring in mould contaminated sliced-bread. Lt. Lebensm. Rdsch., 80, 2, p. 35-8. Mycotoxin quantitative estimations using chromatography with UV-detection. Gorst-Allmann, C. P., and Steyn, P. S. (1979) (TLC method) J. Chromatography, 175, p. 325. Durackova, z., Betina, V., and Nemec, P. (1976) (TLC method) J. Chromatography, 116, p. 141. Howell, M. V., and Taylor, P. W. (1981) (TLC method) J. Assoc. off, analyt. Chemists, 64, p. 1356. Lee, K. Y., Poole, C. F., and Zlatkis, A. (1980) (HPTLC method) Simultaneous multi• mycotoxin analysis by HPTLC with continuous multiple development and two solvent systems of different polarity. In: Bertsch, W., and Kaiser, R. E. (editors): Instrumental HPTLC, Published by Hiithig, New York, 1980, p. 263-73. Scott, P. M. (1981) (HPLC method) Liquid chromatography in the analysis of mycotoxins. In: Trace Analysis, Vol. I, edited by Lawrence, J. F., Academic Press, New York, p. 193 et seq. Castegnaro, M., and O'Neill, I. K. (1982) Environmental Carcinogens-Selected Methods of Analysis, Some Mycotoxins. Vol. 5, IARC, Lyon, 1982.

CHAPTER 1.9 WEIGHER/MIXER FUNCTIONS AND DIVERSE TYPES OF MIXERS AND MIXING-REGIMES

Integrated electronic and microprocessor-based control systems for ingredient handling: Dietrich Reimelt KG, 6074 Rodermark-Urberach, FRG. Reimelt-Atlas SP-80 computer-interfaced ingredient-batching/weighing, checking/ optimiz• ation, production-line control and formulation cost control systems, tailor-made from core intelligence software elements and appropriate hardware. Pneumatic transport of raw materials of variable density, e.g. brans and meals, also brown flours. One-step weigh and mix systems Lift and sift system marketed by Russel Finex Limited, London WC2H 7EQ, UK. Negative vacuum raw material transport systems. Travelling-weigher aggregates. Tweedy weighing and mixing systems for CBP brews and straight doughs. Kerry Flour Handling Systems Limited, Crawley, Sussex RHlO 2PX, UK. Automatic pneumatic transport, load-cell censor weighing, and centrifugal sifting aggregates for flours of diverse type and composite bulk density and particle-sizes flours, e.g. brown flours, specialty flours. Weigher/mixer function concepts and their relative merits. Types (~l mixer and mixer-regimes: Notes and references 737

Single-arm conventional discontinuous (batch) mixers, operating at 15 to 50 rpm, with mixing times of up to 20 minutes. Single-arm high speed discontinuous (batch) mixers, operating at 70 to 100 rpm, with a choice of 2 speeds, e.g. Diosna/Dierks, Osnabriick, FRG; or types HLK-50, S-125, and S-250 manufactured in the GDR by VEB-Biickereimaschinenbau, Halle, GDR. Extremely robust and versatile machines for large and small bakeries, hotels and restaurants, with a high torque at a reduced rpm. A mixer for the craftsman, who believes in fermentation, and who has a mixed trade. Twin-arm, elliptical-orbit, discontinuous (batch) mixers, with the unique cyclodynamic action, of which the Artofex is the prototype. Of Swiss origin, these machines are marketed in the UK by: Artofex Limited, Enfield, Middlesex. The Record Bakery Equipment Co. Ltd of St Albans, Herts ALl UF, UK, market a machine of similar design. Spiral mixers are ideal for use with the CBP, activated dough development (ADD), short• time, or soy/untreated flour processes. Although intended as a discontinuous (batch) machine, it can be integrated into a quasi-continuous system, using interchangeable mixing bowls with a full-length centre column, and non-wrapping spiral. The short mixing-cycle allowing doughs to be worked off on a line system, with a throughput of 3 tonnes/h. Such a system with computer control is available from: All Foods Engineering Services Limited, Newcastle, Staffordshire ST5 6NR, UK. Spirals have gained in popularity in EC countries, owing to their versatility, short mixing-cycle, simplicity and reliability. Design options are: spiral arm only, spiral and central pillar or plinth, fixed/removable bowls, bowl-tippers, etc., from Dierks 'Diosna' range (FRG), Kemper (Austria), Thomas Collins (UK), Eberhardt (FRG), Werner and Pfleiderer (FRG), APV-Baker, formerly Baker Perkins (UK), Sottoriva (Italy), Sancassiano (Italy), Boku (FRG), Oase (FRG), Record (UK), and Artofex (Swiss), etc. Wendel mixers, are multifunctional, with an advanced complex wave path, resulting in alternative short, frequent dough stretching and compression actions, forming a developed three-dimensional gluten network. Ideal for all wheat and rye doughs; the action is especially suited to coarse meal doughs, and soy/untreated flour doughs for 'clean-label' products. This machine is also ideal for biscuit doughs and cake batters. The prototype of these high technology mixers is the Diosna Wendel, which has two wendel-elements, rotating in opposite directions. Type A2-ChTM for 45 kg flour batches, and the A2-Ch-TB for up to 100 kg, manufactured in the Ukrainian SSR of the USSR, are batch mixers with adjustable mixing elements, and fixed mixing-bowl, which can be removed and transported on tyred-wheels. Type SM85 spiral-kneader, manufactured in Yugoslavia by GOSTOL of Nova Gorica, is a heavy-duty machine for doughs of 135 kg. Machine type SM I25 for 200 kg flour has a work• input of 11 to 15 kW, and the smaller SM 85 delivers 7 to 11 kW. The spiral mixing element rotates at 110 to 220 rpm within one half of the machine-bowl, and the ploughshare mounted within the machine-bowl axis, distributes the dough evenly. The machine-bowl rotating in the opposite direction to the mixing-arm, being independently powered by a 2'2-kW motor, its direction of rotation being reversed during mixing. On completion of mixing, the mixing-arm, ploughshare and drive are raised electromechanically to allow removal of the bowl. Intensive discontinuous (batch) mixers, which can be either vertical or horizontal in design, can often be operated on a quasi-continuous basis, owing to the short mixing cycle, thus allowing integration into line-production systems. Those used for the CBP in the UK include the following machines: Tweedy model range 35, 70, 140, 160,200,4400,300 and 6600, giving outputs of 216 to 3300 kg dough/h; Gilbert 35 and 70, or 140; Mono 28, 70 and 100, all introduced with the CBP during the 1960s. These machines delivering energy-inputs of 8 to 11 W h kg - I dough, at 400 to 420 rpm, over 90 to 120 s. However, much energy is dissipated as heat, resulting in dough temperature increases. This, coupled with the 'clean-label' 738 Handbook of breadmaking technology

requirement and use of only organic-based additives, has resulted in a current trenq away from these machines. The Stephan TK 150, top-loading, horizontal mixer, can be used for all mixing requirements, including: doughs, pizza-doughs, pastry, cake-batters, and grinding stale-bread crumb, by changing mixing-heads. It is engineered in the FRG by A. Stephan und Sohne GmbH & Co., D-3250 Hameln 1, mixing speeds being 750, 1500 or 30QO rpm, depending on the product, utilizing a power-rating of 15·5 kW. Maximum dough-loading is 90 kg per batch, rapid mixing and unloading cycles allowing throughputs of about 800 kg/h. This is a high-technology intensive batch mixer with hydraulic discharge, direct into dough-trolley, or onto conveyors. The Collette intensive mixers, engineered in Belgium, represent prototype intensive mixers for the baking and food industries, pioneered during the 1970s. The wheel-in bowls eliminate handling and tipping, with capacities of 5 to 600 litres, and the use of additional bowls provides a quasi-continuous operation. The 1MK 150, engineered in the GDR by VEB Backereimaschinenbau, Halle, GDR, is a very• heavy-duty intensive-mixer, mounted within a twin-standing, which houses the water-dosage unit and the control panel. Driven by a 60-kW motor, transmission is direct via 10 drive-belts, reducing the rpm from 1470 to 415 to 420, delivering an energy-input of 8-10 W h kg- 1 dough, within 2-3 minutes, which is recorded on an amperometer. Raising and lowering of the mixer-bowl is achieved hydraulically, the oil-pump being driven by a separate 3-kW motor. This machine is extremely flexible for wheat and rye flour doughs, allowing throughputs of up to 3000kg dough/h. Using eight machine-bowls, one IMK 150 at maximum output of about 1900 kg/h, is capable offeeding two lines continuously for an oven of 50m2 baking-surface. The horizontal-bar and drum high-speed mixers used in the USA and Canada, range in capacity from 100 Ib to 2500 Ib, operating at two speeds, 35 rpm in the slow mode, and 70 rpm maximum. Power-ratings ranging from 5 hp up to 125 hp. Horizontal mixers can be either of the stationary or tilting bowl design. In the former case, the bowl drum is solidly fixed to the mixer frame, the dough being removed by lowering the electrically operated sliding-door and slowly revolving the mixer arms. The tilting machine bowl design ejects the dough by tilting the bowl hydraulically at a 90 to 140 degree angle. Horizontal mixers are heavy-duty; high• torque machines with transmission ratios of 2: 1. The mixer drum is trough-like with a curved bottom and flat sides and ends, of stainless steel construction, with rounded joints and corners. The drum has a refrigerated jacket, running around it, with external insulation to prevent condensation and refrigeration loss. Dough mixing and development is effected by a rolling, kneading and stretching action imparted by cylindrical bars, which are mounted along the length of the bowl-drum on 2, 3, or 4 opposite arms of a cradle attached to the agitator shaft, a 3-arm cradle having a Y -profile, and a 4-arm cradle that of a cross. The profile of the bars can vary from being smooth and rounded to being curved or sigma-shaped, thus improving traction and mixing intensity. The 3-arm cradle usually also has a breaker-bar positioned at the top rear to absorb the impact, and fold the dough when tossed towards the rear of the bowl-drum. Although these mixers have quoted capacities of 1000, 2000 and 2500 lb of dough, these are only maxima, and experience has shown that much improved mixing efficiency in terms of mixing intensity is achieved by reducing dough loads by about 15 %. Since these mixers are also utilized for the preparation of sponges for the sponge and dough processes on the North American continent, a reduction in weight loading of about 60% for sponge mixing becomes mandatory, owing to the firmer, lower absorption of these doughs. These mixers are marketed by Baker Perkins (APV-Baker); Peerless Machinery Corporation; and Oshikiri HM Series marketed by Gemini, Philadelphia, PA 19115, USA; the American Machine and Foundry Company of Richmond, Virginia 23227, USA, is also a long-established manufacturer of horizontal-bar mixers. The UniPlex and BiPlex intensive batch mixing systems were introduced by Baker Perkins in Notes and references 739

1984. The UniPlex is an intensive mixer with a similar mixing concept to the Stephan TK150, intended for mechanically developed doughs (MDD), ADD, and bulk-fermented systems. However, the UniPlex is intended for the larger operation, requiring more ingredient-feed sophistication, coupled with a choice of three levels of automation. Wheat and rye flours can be accommodated as well as enriched doughs of most types. Four maximum output capacities are available: 1600 kg/h, 2200 kg/h, 3000 kg/h and 4000 kg/h, using power-ratings of35, 45,55 and 75 kW respectively. These output capacities are based on mixing times of2·75 to 3·25 minutes. The BiPlex utilizes a two-stage mixing concept, the spiral mixer-element describing a planetary orbit within a horizontal fixed cylindrical bowl at high speed for about 4 minutes, thus effecting hydration, dispersion, and atmospheric oxygen uptake; the second stage, of about 1 minute duration, involves a high-speed rotation about a fixed shaft, thus completing the development stage. Oxidants synergistic to oxygen, e.g. ascorbic acid and azodicarbonamide perform best with this mixer, yielding short-time doughs. However, untreated flour with a soy-lipoxygenase source to effect oxidation could be utilized. In the case of sponge-and-dough processing, or straight doughs, involving bulk fermentation, the planetary mode only is necessary. Owing to the efficient dynamics, minimal heat is dissipated, reducing undesirable dough temperature rises and the need for cooling or refrigeration. The BiPlex 200 with 2 litres capacity provides 106 kg batches at the rate of 15/h, equivalent to a throughput of 1590 kg dough/h. The high volume output systems have a fully integrated and automated mixer, ingredient weighing and feed facility under microprocessor control, which stores formulations and provides diagnostic information. The main motor power-rating is 22 kW, and the planetary motor 4 kW. The BiPlex process and mixing system has been developed, patented and manufactured by APV-Baker (formerly Baker Perkins Limited) of Peterborough, UK. Continuous dough-mixing systems demand exact and systematic operating procedures, the dough being assembled, mixed and developed in distinct stages, leaving the developer aggregate by extrusion. Processing operations comprise two stages: raw material preparation and dosage, and continuous dough mixing. Sieved and blended flour is transported into the daily-silos and fed to the weigh-head (with load-cells), of the mixing-aggregate. Yeast, salt, shortening and dough improvers/conditioners being prepared in either slurry or solution form, as appropriate, at the preparation-station using special containers and agitation• aggregates. The exact amount of yeast and salt are automatically metered according to the flour weight measured by the weigh-head load-cells. Usually, if the weight of the flour is changed, a synchronization-device adjusts all the liquid ingredients accordingly. However, the operator must check this function before delivery to ensure that the formulation is adhered to, and correct as necessary. Rotational speeds of continuous mixing-aggregates can usually be regulated from 25 to 170 rpm, dough residence times being about 2-4 minutes, depending on the rpm and extrusion outlet adjustment. Mixer-housings are usually cylindrical, with baffle-plates or pins often mounted on the inner surface, to increase resistance during mixing. Dough throughput capacities, depending on chosen rpm, average 500 to 1500 kg dough/h, larger units for 1800 to 3000 kg/h being also available. The use of an active pre-ferment with this mixing system improved its feasibility. Do-Maker and Amflow systems, as commercially practised in the USA, produce an unorientated cell structure in the bread, and a very soft crumb texture, fine grain and high specific volume. The excessive soft, gummy crumb texture, and flavour and aroma reduction being ameliorated by: passing through a conventional make-up process; use of 50% total flour in the pre-ferment; air injection into the developer. Some loss of operational rationalization resulting. Essential processing steps being: an active pre-ferment containing yeast, inorganic nitrogen, flour or fermentable sugars and pH adjustment; continuous production of an assembled dough in a pre-mixer/incorporator from the mature pre-ferment, residual ingredients, high oxidant levels; intensive mixing, at high speed and pressure to full development within a small chamber, anaerobically; direct scale/deposit into baking pans. This latter development-head being a counter-rotating double-arc element at speeds of up to 740 Handbook of breadmaking technology

290 rpm, over about 1 minute, at energy-input levels of O· 3 to 0·4 hp min - 1 Ib - 1 of dough. Production capacity ranges being 4000 to about 7000 Ib h -1. Automatic divider/panning rates approximate to 80 pieces/min. European continuous systems, had to be designed or modified to satisfy the consumer demand for variety- and hearth-breads from wheat- and rye-flours, mixed wheat/rye breads, specialty• breads, producing products of lower specific volumes, higher densities, employing much leaner formulations on average. Whereas, the American systems perform ingredient incorporation or premixing, and actual mechanical dough development in two distinct mixing modes, the European systems perform these two functions within the same machine aggregate. Furthermore, in many cases, European systems do not rely entirely on purely mechanical development, variable bulk fermentation floor-times being allowed to attain full dough maturity, even when pre-ferments are being utilized. The Konpetua continuous system was developed in the FRG in 1967, and built by Werner and Pfleiderer of Stuttgart, the first commercial installation on a large scale being in 1968. The main feature of this aggregate is its mixing flexibility, and ease of adaptation to changing production requirements. The twin rotating mixer shafts, equipped with variously shaped mixing elements are housed in a cylindrical chamber. Production capacities range from 300 to 5400 Ibjh (136 to 2454·5 kgjh), depending on chamber diameter. When a small and a large unit are utilized as a dual system, hourly dough outputs can be increased to around 8500 lb/h (3864 kg/h). Dough consistency is controlled by feedback from a wattmeter, which automatically corrects fluctuations in metered dough water. The developed dough is extruded through an adjustable outlet onto a belt conveyor, and proceeds to make-up aggregates. The Kontinua continuous system, also manufactured by Werner and Pfleiderer of Stuttgart, suitable for standard type bread production from wheat- and rye-flours, and wheat/rye mixtures, offers high volume outputs (see Figs 71 to 74). The two types FMS 400 and FMS 500 deliver output capacities of up to 2000 and 3500 kg dough/h, respectively of mixed rye/wheat• flour doughs; and 1500 and 2400kg/h of wheat-flour dough respectively. Variable speed motors of 42 kW provide an rpm range of 600 to 2200. The Buss-Ko-System List, is a Swiss continuous mixer, consisting of a cylindrical housing, enclosing a mixing worm designed as a helix with interruptions. Sets of mixing protrusions, fixed to the housing, project into the gaps in the helix, so that as the worm rotates, the dough is forced towards the extrusion end. Mixing and development of the dough being achieved simultaneously. The Ivarsson system, commercially introduced in Sweden in 1957, has metering and feeding aggregates for liquid and dry ingredients feeding into the cylindrical mixing-aggregate of horizontal design. The mixing elements are two straight shafts, and one spiral ribbon kneader rotating eccentrically. The ingredients are fed in at one end of the cylinder, being mixed, and then forced by the spiral towards the discharge end, thus effecting dough development. The residence time being controlled by an adjustable extruder outlet is on average 90 s. The average throughput is 100 Ib/minute, the mixed dough being given a 30-60-minute maturation-time, before passing through a conventional make-up schedule. The Strahmann mixer, of German design and manufacture, also attracted interest in the UK during the early 1960s. Modified patents were taken out by Simon of Stockport under the joint name Simon-Strahmann. These modifications included a degree of control over shear and pressure rates during mixing, and the retention of conventional moulding techniques, thus providing products with either accepted standards or finer-grained 'texturized' crumb porosities. Elias, D. G., and Wragg, B. H. (\963) Cereal Sci. Today, 8, p. 271. Eggitt, P. W. R., and Coppock, J. B. M. (1965) Cereal Sci. Today, 10, p. 406. The mixer shaft, rotating at 120-300 rpm, was provided with a series of impellers, with a static shear disc positioned in front of each. The shear discs have apertures of varying dimensions, Notes and references 741

depending on their location along the shaft. The dough is forced through these apertures by the preceding impellers, about 20 in number, driven by a 35 hp motor. The first four sections had open discs with coarsely pitched impellers, thus effecting a premix function. Subsequent disc apertures were reduced, giving pressures up to 30 psi, and resulting in dough development with considerable air occlusion, leading to texturization. Mixing intensity could be controlled by shaft-speed, shear-disc aperture, and feed-rate. Energy-input levels were about 5 W h lb -\ for fine texture, and 4 W h lb -\ for irregular, conventional dough porosity. The whole system is enclosed within a horizontally mounted cylindrical housing. An additional feature of the Simon-Strahmann system was a special patented rotary-divider. This was fitted to the extruder outlet, the dough being extruded into a circular chamber with a 6-segmented scaling rotor, controlled by a pressure-sensitized microswitch, which rotates the rotor as each segment is filled with dough. The dough being discharged from the segments, rounded, given an intermediate proof before sheeting and moulding. Such treatment resulting in an open-textured conventional type loaf. The Oakes continuous mixer/modifier, designed by E. T. Oakes Limited in the UK, was the only continuous system which could be recorded as a commercial success in the UK baking industry. First introduced commercially in 1964, this unit was compact, flexible in product adaptation, and easily cleaned. The dough was extruded as a continuous ribbon, being either put through a standard divider, or an Oakes continuous automatic divider, designed to give better uniformity, and dough-weight accuracy. The dough-pieces then passed through a conventional make-up procedure. A system was designed for the CBP with complete ingredient facilities, dough development, followed by dividing and conventional make-up. Direct panning never found favour in the UK baking industry. Throughput capacities of 1800 to 49501b dough/h were possible with the Oakes mixer/modifier, and a specially designed automatic divider eliminated variations in dough density and consequent scaling weight variations. Continuous feeding of the divider with a constant head of dough from the mixer/modifier in an inert state gave reduced quality difference between bread from bulk fermented and mechanically developed doughs. However, the UK Baking Industry concluded that the disadvantages of a continuous system, viz. reduced flexibility of product types; synchronization problems with conventional make up machine-aggregates; reduced water absorption; and floor space and line integration, compared with the use of CBP batch mixers, could not be justified during the 1960s. Therefore, continuous processing progressively diminished in favour of the quasi-continuous CBP batch system. Socialist community countries (COMECON) applied continuous breadmaking systems of diverse processing techniques and machine-aggregates with much success, after pioneering work carried out in the USSR during the 1950s. After that time, mixing-aggregates suitable for various output requirements for wheat and rye-flour, as well as mixed rye/wheat-flour doughs were developed in most of the COMECON countries as a result of special trade arrangements to avoid excessive competition. In the USSR, during the 1930s work was already under way concerning continuous breadmaking technology under such pioneers as Woronkow, Beljakow, Molodych and Proworichin. In 1944, an engineering and scientific collective in the mechanics laboratory of the WN I I ChP in Moscow under the direction of G. E. Nudelman, began research on intensive mechanical methods of continuous mixing, and the first production installation was realized in 1947. Then followed the development of a continuous two-phase system for wheat-flour dough, the first phase being a liquid pre-ferment, the final doughs being fermented in a carousel system. Nudelman, G. E. (1952) Automatic production line for the manufacture of bread-roll doughs. Collective papers from scientific lectures No. 178 Moscow, Pistscherpromisdat, 1952, (Russian). The N. F. Gatilin bunker-aggregate, was first installed in Soviet bread factories in 1946 for the preparation of rye bread from firm sour-doughs, together with the AZCh oven, for the 742 Handbook of breadmaking technology

production of 100 t of bread per day. However, since then its application has been extended to the production of whole wheatmeal bread from firm sour-doughs, and wheat-flour bread from second grade wheat-flour using a sponge-dough process. For factories with outputs of 20 t per day, a smaller version, the BAG-20 was introduced for wheat-flour sponge-doughs, and rye doughs from firm sour-doughs at up to 30 t daily output. These systems eliminated the use of machine-bowls for sours, sponges and doughs, but the preparation of the pre• ferments (sours and sponges) was on a batch basis. During the early 1970s, Bunker aggregates with continuous-mixing and reduced bulk fermentation-times were introduced. Tschernjakow, B. I. Chlebopekarnaja i konditerskaja promyschlennost (ChKP). 12,9, 33, 1968 (Russian). Such aggregates were designed for outputs of about 30 t of 1 kg hearth-breads per day, using sponges prepared on a large scale from 70% of total flour, and 66% of total dough water. The sponges were fermented for 4'5-5,0 h at 28°C. The final doughs, set at 32°C, remained in a stationary-bunker for 20-25 minutes maturity-time before make-up. This aggregate is fully automated. A similar concept using aggregate L4-ChAG was applied to the production of both wheat and rye bread at 15 t per day. The I. L. Rabinoll'itsch continuous aggregate ChTR, for wheat-flour doughs, utilizes a direct fermentation process, using either 1·5% compressed yeast and 5% to 20% liquid yeast, or 50% to 60% liquid yeast. The dough temperature being set at 27 to 29°C for a bulk fermentation time of 4·5 to 5·0 h. Roiter, I. M. Modern Breadmaking Technology in Industrial Bakeries, Kiev, Published by Technika, 1971 (Russian). The W. M. Dontschenko continuous aggregate ChTU-D, utilizes a Ch-12 mixing-aggregate (Fig. 24, item 5) with discharge into a worm-pump, which further develops the dough before it is transported upwards through a pipeline into the divider. The A2-ChTT continuous mixing-aggregate, exhibited at the 1987 Leipzig Fair, is intended for throughputs of 1300 kg/h at a power-rating of only 3 k W. The C::echoslovakian manufactured continuous doughmaking plant series KVT 1000, J500 and 1800, producing 1000, 1500 and 1800 kg dough/h, illustrated in Fig. 75, although intended as a complete line assembly, can also be adapted for non-line systems. This system is utilized for mixed wheat/rye-, or rye-flour processing, at a power-rating of 12kW, the KVT 1000 throughput ranging from 850 to 1000 kg dough/h. This is a well-engineered plant, which has found very wide acceptance in the GDR baking industry, as well as other baking industries of the COMECON countries. The FTK 1000 continuous doughmaking plant, which is also well engineered, is manufactured in Hungary, and also exported throughout COMECON. It is capable of outputs of 1000 kg of rye-flour dough/h, or 810 kg/h of wheat-flour dough. This plant has centralized control systems, but offers control units on individual aggregates, utilizing a building block elemental design. The illuminated central control panel comprises the grouped control mechanisms, automatic systems making full use of transistors and thyristors for motor control. Grouped control-mechanisms are provided for the following functions: energy-distribution; programming; instrumentation; switches and preset; malfunction warning lights; switchover from manual to automatic control; safety devices for electrics; illuminated display for all functions. Sequence numbering on the control panel clarifies the construction and schematic layout of the FTK 1000 plant. In the Federal Republic ()(Germany (FRG), mechanization and automation of the sour-dough acidification and perpetuation processes are described by D. Thorner of Dusseldorf. Thiirner, D. (1982) Getreide Mehl und Brot, 2, p. 44-7 (German). Patented as the 'Isernhager natural dough-souring process', this process can be applied to the production of a complete range of rye-flour bread, providing a uniform supply of sour-dough Notes and references 743 from Monday to Saturday with flexibility. The maturing time of the sour is 18 h, and the required amount of sour, about 36 kg, for each batch, is directly metered into the mixer. In the case of the 'salt/sour process', the amount of sour-dough for a given flour mix is read off from tables. Any mature sour not processed within 6 h of the full maturity-time, is transferred to the starter-machine, and then flows into the dosage tank after 24 h, which contains enough sour-dough for a day's production. The plant is intended for sour-dough batches of 1500 kg, but can be increased to 2000 kg. When two starter-machines are coupled with one dosage• tank, outputs of up to 4000 kg of sour-dough/day are possible.

CHAPTER 1.9 WEIGHER-MIXER FUNCTIONS AND DIVERSE TYPES OF MIXERS AND MIXING-REGIMES

A joint design and construction between VNI in Vienna and Reimelt of Frankfurt/FRG, has produced a patented system for the continuous preparation and storage of natural sour• dough. Foramitti, A. (1982) Getreide Mehl und Brot, 2, p. 47-50 (German). This is a two-stage process, using a fermentation-tube and a tank. The first stage can be stored for 4 days, under control, without excess acid formation or damage to the organisms, thus permitting stoppages as and when necessary. The second stage provides a uniform quality sour for bread production. Selection of process parameters; fermentation power of sour• dough yeasts are maintained to give a balanced lactic:acetic acid content. The first plant is in operation at the VNI, one of Europe's largest bakeries in Vienna, producing up to 4·8 t sour• dough/h, commissioned in 1979. This fully mechanized, continuous, automated plant can be operated by just one person and guarantees homogeneous sour-dough and consistent bread quality. Short-time (no dough-time) processes, involving either totally mechanical, or a combined mechanical/chemical development process, have found favour in some countries. However, the elimination of fermentation results in a bread flavour, and crust and crumb structure which is unacceptable in many countries with discerning consumers and bakery technologists.

Sheeting methods for dough development, using sheeting-rolls and repeated passage of doughs through them are utilized in countries where energy resources are limited, and the cost of expensive mixers prohibitive. In countries such as Peru, parts of Spain, south-east Asia, and parts of Africa, labour-intensive methods remain efficient owing to the plentiful supply of manual labour. Where bread is produced from composite-flours, e.g. wheat/maize, wheat/ sorghum, wheat/millet, or wheat/triticale, in various ratios, low-power pressure sheeting remains an ideal form of dough development. Bushuk, w., and Hulse, J. H. (1974) Cereal Science Today, 19, 8, p.424-7. produced bread of acceptable volume, grain, texture and colour from composite flours of80% CWRS (Manitou) wheat-flour mixed with up to 20% non-wheat flour, using toO% CWRS wheat-flour as control raw material. The doughs being mixed by hand, and rested for 30minutes before dividing and passing, in to small pieces of equal weight, through three sets of sheeting-rolls, using 10 passes in the case of each set. Thus effecting mechanical dough development. After a to-minute first proof at 35°C and 80% RH, the doughs were again sheeted successively through three sets of rolls adjusted to increasing roll-gap. The dough-pieces were then moulded either manually or mechanically, and panned. Final-proofing was 55 minutes at 35T and 80% RH, baking at 221°C for 25 minutes. Results were also compared with the same flours processed by the CBP, and Canadian remix-test bake procedures. The conclusions were that simple dough development by pressure sheeting, gives results comparable with those obtained by high-energy mixing procedures. 744 Handbook of breadmaking technology

Kilborn, R. H., and Tipples, K. H. (1974) Cereal Chemistry, 51, 5, p. 648-57, using a Canadian CWRS wheat-flour of 12·5% protein, confirmed the efficient development work performed by sheeting-rolls at much reduced energy input levels, compared with high-speed mixers. The actual rate of energy input is only slightly less than that imparted by an intensive pin-mixer. This confirms the importance of the mixing parameters 'specific mixing-intensity' and the type or mode of work-input, and dough structuralization, i.e. compression (pressure), elongation (stretching), or shear forces. Excessive sheeting of doughs gives rise to symptoms of loss of resilience, and permanent deformation. However, structuralization by sheeting at optimal intensity (about 20 folds), will create over 1 millions layers, and simultaneously, the dough becomes reorientated through a 90 degree angle at each folding-action, thus creating a two-dimensional (cross-hatched) versus a unidirectional network formation. Research has indicated that the sheeting-procedure can effect energy savings of up to 70%, compared with mixer energy-inputs, and produce bread of equal quality to that produced by the conventional, latter technique. This concept has potential, but requires line-flow mechanization/automation, in order to fix process control parameters. Integration into a continuous mixing system is indicated, allowing reduced or no-fermentation-time doughmaking. The Reddi-sponge system, can completely eliminate the fermentation process stage, enabling the baker to save about 4 hours in bread and roll production. On completion of mixing, and a 15-minute rest period, doughs can be divided, proofed and baked.

Pre~rerment systems, however, protect bread quality and flavour. Pre-ferments can be varied in composition to include soluble nutrients for the yeasts, and sours for both wheat- and rye• flour processing; up to 25% of total dough salt content; and pregelatinized/partially hydrolysed biopolymer-rich raw materials. Their viscosity can be varied by adding from 10% to 60% of total flour content; temperature control, depending on maturation-time, being varied from 20°C up to about 40°C as required. Such procedures allow floor-times of 10-15 minutes, or direct dividing, proofing and baking. Maes, E. (1959 and 1960) Automatic bread machine. Backer und Konditor, 13, 19, p.9, 1959 (German). Brot und Gebiick, 14, 1, p. 1, 1960 (German). Maes, E. (1964) Brot und Gebiick, 18, 6, 1964 (German). Other innovations include the use of liquid-yeast, and the application of biotechnology in the form of specific enzymes, e.g. amylases, proteinases, amyloglucodisases, pentosanases, lipoxygenases (soy source, marketed in the USA as 'Wytase W-52' of J. R. Short Milling Company, Chicago, IL 60606), cellulases, and oxidoreductases, etc. Yeast species, other than S. cerevisiae, which can be included in pre-ferments include the following strains: S. delbriickii, for rapid flavour production; Candida lusitaniae, for increased flavour development; Candida krusei, Pichia saitoi and Torulopsis holmii as starters for sour• doughs: Candida milleri and S. exiguus for wheat-sours and pannetoni bread (Italy); S. rouxii for sweet-dough ferments; Torulopsis cellulosa, and T. candida used as starters for sangak bread (Iran); also S. rosei for all frozen-dough baked products. The basic control parameters of yeasts, sours and their pre-ferments are: nutrient food supply (up to 6% is optimum); water content (100% of flour absorption gives the most rapid digestion rate); dough temperature (30 to 40°C is appropriate for short pre-ferment-times); medium pH range 4·0 to 6·0 (for enzymic activity); flour content (10% allows rapid digestion, 25% is a good average concentration); salt concentration (25% of total dough salt content controls cell osmosis). Notes and References for Part 2

CHAPTER 2.1 FERMENTATION OF WHEAT AND RYE-FLOUR DOUGHS

Yeast-forms for breadmaking include: fresh compressed; fresh cream liquid; dry active; dry instant active. Water contents are, 68% to 75%, 80% to 82%, 6% to 8% and 4% to 6% respectively. Relative storage life is approximately 3 weeks, lOdays, 2 to 12 months, 1 year plus, respectively. Fresh compressed requires dispersal in water before mixing. Fresh cream liquid can be metered directly. Dry active requires rehydration in water at 40°C for 15 minutes before addition. Dry instant active can be dry blended with dry raw materials, or added at a later stage. Compared tofresh compressed used at 1 part by weight, fresh cream liquid requires 1·5 to 2·0 parts, dry active 0·5 parts with extra water, and dry instant active 0·4 parts with extra water added. Frozen-dough yeast, is a strain engineered to become desensitized to sub-zero temperatures. This permits a normal proof-time after about 90 days storage at - 20°C of the frozen dough products. Other strains of yeast require extended proof-times, with no guarantee of consistent results. Compared with the use of fresh compressed at 1 part, frozen-dough yeast requires only 0·4 parts with the appropriate 0·6 parts water added extra, to adjust the weight difference. This yeast requires no rehydration, the frozen yeast product being transferred from sachet to mixer bowl. It is viable for about 1 year when stored at -18°C. Its relatively slow fermentation rate makes it also ideal for bulk fermentation and Viennoiserie work. Also, whereas about 5% fresh compressed yeast is required for frozen-doughs (flour weight), the frozen-dough yeast can be used at the 2% level for lean doughs. Liquid yeast is gaining in popularity for industrial bakeries, owing to the advantages of bulk• handling systems, being delivered in refrigerated tankers depending on climatic temperature. Liquid yeast has been used in the USSR for many decades in the large city industrial bakeries. The average dry matter content of liquid yeast is 20%, compared with about 30% for fresh compressed yeast.

CHAPTER 2.2 INDUSTRIAL PROPAGATION AND PRODUCTION OF YEAST FOR THE BAKING INDUSTRY

Yeast reaction products: 100 parts of monosaccharide reacts with the yeast enzymes to yield 49 parts of ethanol and 47 parts of carbon dioxide, together with such other organic by• products as glycerol; lactic, acetic, malic and succinic acids; aldehydes; fuse1 oils; and numerous flavour compounds. Belova, L. D., et al. (1985) at the WNIIChP (All-Union Research Institute for the Baking Industry) Moscow, USSR, have shown that hydrolysed starch syrup, derived from potato or wheat can be used instead of molasses for the production of baker's yeast, at biomass yields 61-63%. Khlebopek. Konditer Prom.-st., 4, p.40-1 (Russian). 745 746 Handbook of breadmaking technology

The yeasts by S. Burrows, in A. H. Rose and J. S. Harrison (editors), Academic Press, New York, Vol.3, 1970, p.349-420. Harrison, J. S., in D. J. D. Hockenhull (editor), Progress in Industrial Microbiology, Vol. 10, Elsevier, Amsterdam, The Netherlands, 1971, p.162-3. Microbial technology. In H. J. Peppler and D. Perlman (editors), Academic Press, New York, Vol. 1, 1979, p.157-85. Reed, G. In G. Reed (editor), Prescott and Dunn's Industrial Microbiology, 4th edn, A VI Publishing Co., Westport, CT, 1982, p.593-633. Trivedi, N. B., Cooper, E. J., and Buinsma, B. L. (1984) Food Technology, 38, p.51-7.

2.2.1 Yeast Physiology Wang, H. Y., et al. (1977) Biotechnology and Bioengineering, 19, p. 69-86. Grossman, M. K., and Zimmermann, F. K. (1979) Mol. Gen. Genet., 175, p.223-9 Cohen, J. D., et al. (1984) Mol. Gen. Genet., 196, p.208-16.

2.1.2 Improvement of Industrial Yeasts Trivedi, N. B., and Jacobson, G. (1986) Recent advances in baker's yeast. In M. R. Adams (editor), Progress in Industrial Microbiology, Vol. 23, Elsevier Applied Science. Entain, K. D., and Frohlich, K.-U. (1984) J. Bacteriology, 158, p.29-35. Car/son, M., et al. (1983) Molecular Cell Bioi., 3, p.439-47. Toda, K., and Yale, I. (1979) Critical glucose concentration for catabolic repression. Biotechnology and Bioengineering, 21, p.487-502. Rogers, D. T. and Szostak, J. W. (1985) of the US Genetics Institute, US Application 796,551 dated Nov. 8, 1985. Method of yeast-biomass production suppression and increased leavening-power (carbon dioxide and ethanol production). Societe Industrielle Lesaffre, UK Patent 1,593,211, 1979, Method of industrial hybridization of baker's yeast meiotic spore clones from strains with desirable properties (rapid and slow rates of fermentation). European applications for leaner doughs demand more rapid fermenting strains. Commercial yeast strains can either be constructed by the classical hybridization techniques, or by protoplast fusion after cell-wall digestion with specific enzymes. van Solingen, P., and van der Pratt, J. B. (1977) J. Bacteriology, 130, p. 946-7 is an example of fusion between yeasts achieved by a commercial yeast company. Spore clones are not always haploid (n chromosomes), and often exhibit sporulation; resultant crosses can give hybrids which exceed the diploid (2n chromosome) number. Digestion is carried out in an osmotically stabilized medium to protect the protoplasts from lysis, the two desired strain pro top lasts being mixed in the presence of polyethylene glycol and calcium ions. This results in spheroplast-agglutination followed by fusion. Numerous hetero- and homologous fusion ratios are possible, multinucleate pro top lasts being formed. Sexual reproduction involves three phases: plasmogamy (plasmic-fusion), karogamy (nuclear• fusion), and meiosis (reduction division). The plasmic-fusion mixture is then plated on isotonic recovery agar, where karogamy (nuclear-fusion), cell-wall regeneration and growth takes place. Owing to participation of several nuclei in this process, a genetically unstable hybrid nucleus may result. At the subsequent mitotic events of cell to colony growth, chromosomes are randomly lost, therefore each colony recovered from a protoplast fusion experiment can consist of many variants, which differ in chromosome content. In the case of Notes and references 747

Baker's yeast (S. cerevisiae), the haploid (n chromosome) stage is rare and short-lived. It occurs during meiosis (reduction division), and is normally restricted to the formation of the ascospores, which copulate immediately on release from the ascus. The diploid (2n chromosome) phase is characterized by the formation of large cells, after plasmogamy and karyogamy have yielded the zygote, which sooner or later reproduces by budding on a large scale. The budding process results from mother cells forming small bladder-like protrusions, which result from a combination of cytoplasmic and nucleic material, the resulting daughter• cells eventually being pinched off as independent living entities. Protoplast-fusion experimentation can provide problems in the selection of a heterologous fusion product. This can be effected by utilizing a number of techniques: -the industrial strain can be converted into a mitochondrial DNA-less petite, which can be fused to a laboratory-cultured strain with auxotrophic markers and the desired gene properties, e.g. maltose production. The resulting heterologous fusant can then be selected on a small amount of medium, containing glycerol as a non-fermentable source of carbon; -another procedure, as described by Putrament, A., Baramowska, H., and Prazmo, W. in Molec. Gen. Genet., 126, 1973, p.357-66, two industrial strains can be treated with manganese, in order to create mitochondrial point mutations, resulting in respiration deficiency or resistance to mitochondrial specific antibiotics (e.g. oligomycin, chloramphenicol and erythromycin). The heterologous fusant is then selected depending on complementary petite mutations that restore growth on non-fermentable substrates, or a double antibiotic resistance. Both techniques depend on the complementation of cytoplasmic markers, and there are no guarantees of karogamy (nuclear fusion). Karogamy requires the presence of a dominant selectable marker from each of the two strains to be fused. Selectable markers are few in S. cerevisiae, but marker genes known as CUPI (copper resistance), and ROC (resistance to the disinfectant roccal) have been reported by Broach, 1. R. in J. N. Stratern, E. W. Jones andJ. R. Broach (editors), The Molecular Biology of the Yeast Saccharomyces-Life Cycle and Inheritance, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, 1981, p.653-727. Protoplast fusion can now be induced electrically, thus eliminating the use of polyethylene glycol. An alternating current of chosen frequency, producing a microsecond pulse, induces an electric dipole in the spheroplasts, resulting in a binding of the protoplasts to one another, and the formation of protoplast chains between the electrodes. The microsecond pulse causes localized disruption at the point of protoplast/protoplast interface. This technique gives up to 100% efficiency in a large mass fusion chamber, although fusants from microliter fusion chambers are difficult to recover. A baker's yeast strain was produced by protoplast-fusion by Universal Foods Corporation, being the subject of U.S. Patent Appl. 503,323,1983, due to Jacobson, G. K., and Trivedi, N. However, this strain was constructed by utilizing complementary spontaneously occurring petites found in commercial strains. The fusants were selected on hypertonic glycerol, and then streaked on non-selective medium. The clones from this medium were then screened on glycerol, acetate and sucrose media. Colonies showing good growth on these media, indicate stable regeneration. Clones showing at least 75% of parent strain yields can then be evaluated in various dough systems, containing flour with no additives as control; flour with 2% flour weight of salt; and flour with 2% added salt and 20% flour weight of added sucrose. In each case doughs are made by adding 15 ml of water, containing 50 mg of yeast solids. In each case, total carbon dioxide over a 4 hour period, recorded every 30 minutes, is measured barometrically; plots being made as total gas evolved, and rate of gas liberated during each 30-minute period. Such tests are an indicator of the organism's resistance to high osmotic 748 Handbook of breadmaking technology

pressures, and relative independence from nitrogen sources from yeast-foods, often added in bakeries. Activity in lean doughs, and in the presence of salt are also important criteria. Maltose is the predominant sugar in flour, only trace amounts of glucose and sucrose being present, and maltose fermentation is quite sensitive to the addition of salt. Sucrose, used at high concentration in excess of a dough's leavening requirements, has an inhibitory effect on fermentation, repressing the maltose utilization system of the yeast. Therefore, strains which are designed for sweet doughs do not require an active maltose utilization system. Yeast strain vitality, is measured as total gas evolved and linear rate of gas production over a 4 h period, using the three dough systems described above. Yeast is classed as a unicellular eukaryote (Greek: eu = normal/typical) since, in common with plants and animals, it has a well-defined nucleus with chromosomes, which divides by mitosis. Bacteria have no nuclear membrane, or endoplasmic reticulum and mitochondria and do not show sexual reproduction. Therefore, yeast can be utilized in eukaryotic molecular biology. This involves 'recombination' or the crossing-over between parts of chromosomes, and the reassortment of chromosomes. A typical haploid yeast has a single set of 15 or more chromosomes, two such cells of opposite mating types, a and b, can fuse, their nuclei fusing to form a diploid nucleus with two complete sets of chromosomes. During meiosis (a phase of sexual reproduction), the chromosomes become double structures, forming two chromatids. Homologous chromosomes then pair and exchange parts of their chromatids by crossing-over, thus four haploid sexual spores form, each spore can then have a new gene combination different from the parent cells. Genes on the same chromosome recombine by cross-over, and genes on different chromsomes become shuffled as chromosome pairs reassort. Biological yeast activity, can be enhanced by mixing with other ingredients which promote the fermentation process. Such mixtures can be dried down to 10% moisture, and stored for up to 3-month periods with improved leavening power, compared with the use of the control yeast. Dough fermentation times can reduce by 50-80 minutes, and bread quality be improved. Chernaya, L. S., et al. (1986) Klebopek. Konditer Prom.-st, 5, p. 28-9 (Russian), at WNIIChP (All-Union Research Institute of USSR). Chernaya, L. S., et al. (1986) Klebopek. Konditer Prom.-st, 7, p.25-8 (Russian), at the Vses Nauchno-Issled. Institute Khlebopek. Prom., Moscow, USSR. Waste bread-crumb can also be hydrolysed with either acid at pH 1·6 and lOO°C, or alpha• amylases followed by amyloglucosidase to produce low-molecular-weight polymers at 60°C. Such hydrolysates act as useful substrate starters for both yeasts and lactobacilli in wheat and rye bread production. Pashchenko, L. P., et al. (1986) Klebopek. Konditer Prom-st, 8, p. 81-3 (Russian), at Voronezh. Tekhnol. Institute, Voronezh, USSR. Use of bread-crumb hydrolysates in liquid rye-starters. Berchtold, J., and Meuser, F. Eur. Pat. Appl. EP 154,135 Sept. 11,1985. Lieken-Batschneider Miihlen und Biickereibetrieb GmbH: Amylolytic flour/crumb hydrolysate for bread dough. A perpetual liquid yeast system for preparation in the bakery was developed by A. I. Ostrowski in the USSR. A gelatinized flour/water suspension is initially fermented at 48-54°C with thermophilic lactobacilli. The resultant high lactic content mash is then cooled to 28-30°C, transferred to another container and used as a substrate for yeast propagation using various strains. After maturation, a definite amount of the mature liquid yeast is taken for doughmaking, and replaced with fresh substrate. This maintains the propagation cycle of the liquid yeast. Such a product is economic in use and produces a flavourful baked product, but its preparation must be under careful aseptic control to avoid wild-culture contamination. Noles and references 749

2.2.3 Post-fermentation Yeast Technology Fresh compressed or cake yeast, quality standards should include a sensory evaluation of colour, consistency, smell and taste. Other quality parameters should include: moisture content (maximum 75%), time required to reach a standard 70mm gassing height should not exceed 75 minutes, and the shelf-life at 35°C not less than 48 hours. Samples should be evaluated for technical culture purity, and glutathione content (proteinase activation). For bakeries, fermentation-speed is the first priority. A standard dough proof height of70 mm in a cylinder, should be attained within 45-52 minutes. Dry-yeast, whether in pellet or granular form, should contain a maximum of 10% dust material, and a maximum moisture limit of8%. A storage-life of not less than 12 months, at a moisture maximum of 8% should be a realistic standard. The 70 mm cylinder proof height should be realized within 90 minutes. Instant active dry yeast (lAD Y), was introduced in the 1960s by Gist-Brocades to overcome the problem of rehydration. Porous, cylindrical shaped particles providing a larger surface area, and instantization. Frozen-dough yeast, for use in doughs for frozen products, as well as liquid yeast, with about 20% solids for use in industrial bakeries, are latter-day developments in Western Europe.

CHAPTER 2.3 CHEMICAL CHANGES IN YEASTED DOUGHS DURING FERMENTA TION

Sponge, pre-ferment, sour-dough andftnal-dough convert an initially dense, inelastic dough• mass into a physical state which can be leavened by the gaseous products of fermentation, simultaneously producing flavour and aroma substances. The final result is a fully 'ripened or matured' dough for baking. Dough-maturation, can only be achieved when the following prerequisites proceed in a systematic manner: adequate gassing immediately after mixing; optimal physical dough properties for machining: adequate elasticity for gas-retention; adequate protein and starch hydrolysis products for crust-colouration, flavour and aroma. Dough fermentation is essentially an anaerobic process, carbohydrate being utilized by the yeast cell to produce energy, the by-products being alcohol and carbon dioxide, in the absence of oxygen. Many en::ymes participate in the series of intermediate stages of anaerobic breakdown, known as the tricarboxylic acid (TCA) cycle. The collective ::ymase-en::yme complex in yeast, hydrolyses the monosaccharide molecule to alcohol and carbon dioxide (two molecules of each). Baker's yeast (S. cerevisiae) is capable of fermenting most types of sugar in dough, e.g. glucose, fructose, saccharose (sucrose) and maltose. Glucose and(ructose are fermented first, almost spontaneously, followed by saccharose, which can be hydrolysed extracellularly to glucose and fructose by the periplasmic invertase. The activity of this external invertase, and its concentration depends on cultural conditions, the appropriate gene having been sequenced to encode a 1·9 kilo base pair (kb) and a 1·8 kb mRNA, the former being under glucose regulation, encoding the external invertase. Chu, F. K., Watorek, w., and Maleg, F. (1983) Arch. Biochem. Biop/tys., 223, p.543-55. Taussig, R., and Carlson, M. (1983) Nucl. Acids Res., tt, p.1943-54. Car/son, M., and Botstein, D. (1982) Cell, 28, p. 145-54. Carlson, M., Taussig, R., Kustu, S., and Botstein, D. (1983) Molee. Cell. Bioi., 3, p. 439-47. 750 Handbook of breadmaking technology

Invertase, is encoded by anyone of six genes of a SUC polymeric system, comprising both a cytoplasmic, and a peri plasmic enzyme. The exact number of SUC genes in industrial yeast strains is not certain, and can vary depending on which ones are present, and their respective copy-number (ploidy of the chromosome on which they reside). Gene dosage has been shown to influence yeast activity, as reported by Grossman, M. K., and Zimmermann, F. K. (1979) Molec. Gen. Genet., 175, p. 223-9. The cytoplasmic (internal) invertase concentration of the cell remains relatively stable. The products of invertase action, glucose and fructose then diffuse into the cell with the help of phosphorylation. Van Steveninck, J. (1969) Arch. Biochem. Biophys., 130, p.244-52. Shortly after mixing of the dough, all saccharose (sucrose) molecules have been converted by the invertases to glucose and fructose. Carbohydrate fermentation by yeasts in general follow a definite scheme according to Kluyver, viz. glucose is the most widely fermented sugar by all yeast species; if a yeast ferments glucose, it will also ferment fructose and mannose by the Embden-Meyerhof• Parnas pathway (EMP); raffinose is only fermented when saccharose (sucrose) is also present in the anaerobic system. S. cerevisiae is only capable of splitting off the fructose molecule from raffinose, the disaccharide melibiose not being digested by baker's yeast strains. Some yeast species can ferment di- and trisaccharides, and others, e.g. S. diastaticus, even ferment starch. Yeasts cannot utilize as many types of sugar under anaerobic conditions of metabolism as they can over the aerobic respiratory route. Maltose fermentation is important in lean doughs, its metabolism also being controlled by a polymeric gene system, five unlinked genes having been identified; as with the SUC system, no single strain carries all of them, but the presence of anyone of these results in the ability to ferment maltose. The MAL genes are more complex than the SUC system, being made up of three factors: a regulatory gene, the enzyme maltase (alpha-glucosidase), and maltose permease. Both permease and maltase are induced by the presence of maltose, and repressed by glucose. Naumov, G. I. (1971) Genetika, 7, p. 141-8. Naumov, G. I. (1976) Genetika, 12, p.87-100. Cohen, J. D. et al. (1984) Mol. Gen. Genet., 196, p.208-16. Maltase repression by glucose, manifests itself in three forms: (1) enzyme inhibition, (2) enzyme inactivation, and (3) complete repression of enzyme synthesis. Siro, M., and Lovgren, T. (1979) Eur. J. Appl. Microbiol. Biotechnol., 7, p.59-66. Galactose, is fermented by all strains of baker's yeast, and some strains can also ferment the trisaccharide melezitose, the disaccharide trehalose, and alpha-methyl glucoside. Where hydrolysed whey is used as an ingredient, the lactase enzyme system becomes of interest taxonomically. In lean doughs, which often contain isomaltose, the ability to utilize alpha• methyl glucoside could be useful for cleavage of the alpha-I-6 bond. Frankel, D. G., in the J. N. Strathern, E. W. Jones, and 1. R. Broach (editors), The Molecular Biology of the Yeast Saccharomyces-Metabolism and Gene Expression, Cold Spring Harbour Laboratory, Cold Spring Harbor, New York, 1982, p. 1-37. Alcoholic fermentation by yeasts can be analysed into the following stages: Glycolysis Activation of the intracellular hexoses by phosphorulation. Splitting of the hexose-diphosphate to form a phosphorulated triose. Formation of pyruvic acid. Conversion of pyruvic acid to carbon dioxide and alcohol. Good baking activity, is dependent upon genes and gene-systems which feed carbohydrates into glycolysis, actual glycolysis, and the TCA cycle. Notes and references 751

Genes involved in nitrogen metabolism and storage carbohydrate synthesis are also important. Rate ofcarbonflow through the glycolytic pathway is crucial to both yeast production, and its baking application. Comparing the short times ofleavening with production propagation, i.e. 2-4 hours v. 12-18 hours. Pre-ferments and yeast-foods are desirable to improve the biological activity of the substrate, since leavening is an entirely anaerobic process, and the rate at which the organism can feed hexoses through glycolysis is of paramount importance. Yeast invertase activity, can be evaluated from the amount of reducing sugar formed within 10minutes from a 15% saccharose (sucrose) solution at pH 5·2 and 60°C, by a yeast suspension containing 6·2 mg dry-cells/ml. Carbohydrate utilization of the yeast cell depends on the conditions; during fermentation (anaerobic), only 10% is utilized for cell growth, whereas during propagation 50-60% is utilized for cell growth (aerobic). Thermophilic yeasts, compared with the mesophils (e.g. baker's yeast), have fermentation temperature optima of 39-40°C, thriving in acid media. Thermophils can be used for wheat• flour doughs and sponges, fermenting at 40°C, producing carbon dioxide and alcohol at a rapid rate. Final proof-times are also much reduced. Bread dough, being a biological filled-polymer system containing many enzymes is best regarded as a 'redox-process', involving the simultaneous transfer of electrons for ionic or covalent bonding. During fermentation, this oxidation-reduction system is controlled by the desmolase group of enzymes, which are flavoproteins with a prosthetic group. The hydrolase enzyme group, controlling hydrolysis and resynthesis of saccharides, amides, proteins and esters, have no such prosthetic group in the molecule. The redox-potential, or rH scale, can be divided into 0-15 at the strongly reducing end, and 25-41 at the oxidation end. Wheat-flours show rH values within the range 15-19, with the higher extraction flours around 15. Wheatgerm, being strongly reducing has rH values between 6 and 7. Rye-flours tend to be between 17 and 18. After 2 hours fermentation, rH values can fall to 17 in the case of wheat doughs, owing to progressive reduction. The rH value, represents the electrical potential developed when the oxidants and reducing components of the dough system reach equilibrium, its magnitude depends on pH and temperature. Since the changes in pH are relatively narrow, the rH scale provides a broader spread for more meaningful interpretation. On the basis of measurements of aerobic and anaerobic rH potential and pH offermenting bread dough, mathematical models of autolysis and fermentation can be formulated. Zlobin, L. A., et al. (1986) Vses. Zaochn. Inst. Pishehevoi Prom.-st, 9, p.22-23. This is an important contribution to the biotechnological control and CIM of industrial baking. Conventional baking processing techniques require considerable time and floor-space, and are labour-intensive on an industrial scale. Therefore, techniques are constantly being researched to rationalize the various process stages involved: mixing, ripening (maturing), make-up (work-off), proofing, baking and cooling. Mixing innovations include increased mixer energy input levels to effect a mechanical dough development. This is complemented by mixer design, involving bowl-shape, mixing-element contour, and path swept out by the rotation. Dough-ripening (maturing) innovations are represented by: Liquid pre-ferments and sponges containing 10-25% of total flour weight, with appropriate temperature, yeast and salt adjustments; application of biotechnological techniques involving fungal amylases, protinases, and hemicellulases, etc.; the addition of various oxidants and reducing agents 752 Handbook of breadmaking technology

(where legislation permits) to accelerate physical changes; substrate supplementation in the form of yeast-foods. Make-up and Proofing innovations comprise 2-6 measuring-pocket volumetric dividers with good scaling-accuracy due to servo-motors controlled from in-line check weighers. Supertex moulder/panner for tightly moulded four-piece, and single-piece pan breads; and cross-grain moulders, which mould the dough in two directions to improve texture; marketed by APV• Baker. Air conditioner final-proofers either free-standing or integral with tunnel-ovens, followed by automatic lidding units. Baking and cooling innovations: indirect fired tunnel-ovens with forced convection, with a choice of gas or oil firing, automatic heat-modulating burners allowing rapid and precise zonal temperature control; automatic depanning units, and travelling band conveyor coolers with air-conditioning.

CHAPTER 2.4 WHEAT- AND RYE-SOURS AND SOUR-DOUGH PROCESSING

Wheat-fiour sour-doughs, although not yet widely accepted for leavening, owing to the lack of standardized manufacturing techniques, are applied in Spain, San Francisco (USA), Central and Eastern European countries, and in Scotland in the form of 'barms'. Sour-dough standardization and development, begins with the careful choice of raw materials and starter-cultures during the initial or first stage. Type and species of microflora, temperature, dough-yield (dough-firmness), and standing or maturing-time, will all determine the acidity-index, flavour and aroma, and crust/crumb characteristics of the final bread. Wheat sour-dough cultures, consist of various species oflactobacilli, and yeasts which ferment under acidic conditions, e.g. pH 3·8. Mother-doughs, 'masa madre' (Spanish), or 'Mutterteige' (German), contain the sour-dough cultures in very firm flour/water doughs. Their exact preparation is usually a closely guarded secret, perpetuated over generations with both individualism and idealism. Mother-doughs can be stored overnight at 2-8°C for up to 8 hours, acidity depending on temperature and storage-time. Their application in latter-day breadmaking is very appropriate for the upgrading of wheat bread from a bland, yeast-raised, mundane food commodity. It involves a three-stage process over about 3 days to obtain the desirable flavour intensity and acidity• index (Siiuregrad) of about 24, at final dough pH 3,8-4,0. Ideal flour ash contents for this fermentation are 0·55% to 0'65%, i.e. flour types 550 to 650. Sour-dough bacteria, depending on type and species, have the capability of converting citric and malic acids in flour into lactic and acetic acids, which enhances bread flavour considerably. San Francisco sour-dough French bread, continuously made for over 100 years, contains the yeast S. exiguus and Lactobacillus sanfrancisco, which coexist within the pH range 3'8-4'5, the lactobacillus bacteria preferring to ferment maltose, the yeast not competing with the bacteria for this sugar. Scottish barms, are prepared from starter-cultures containing hop-infusion, malt flour, and a portion of old-barm. This is fermented for 3-4 days. On reaching maturity, the barm can be added to 25% flour sponge or a 20% flour pre-ferment. Wheat- and rye-sours can be dried and milled to fine powders for reactivation. Freeze-dried products offer the best protection for the microorganisms from heat-damage during manufacture. Such products allow a one-step process of about 3 hours duration for the production of rye bread, compared with a 3-day/3-step traditional fermentation schedule. Notes and references 753

These products give consistent quality, and uniform dough souring at acidity-indices 20-24 for wheat-sours, and 40-44 for rye-sours. These biologically produced sours are used at about 10% of total flour weight. In the USA, such sours are manufactured by the Caravan Products Company Inc., NJ 07512, for wheat and rye doughs, marketing and shipping to Europe being handled by Richards International Ltd, 40 East 34th Street, New York, NY 10016. In the FRG, similar product ranges are marketed by: Dr. Otto Suwelack GmbH & Co., 4425 Billerbeck; Bocker Sauerteigprodukte, Minden 4950; Ulmer-Spatz, Ulm (Donau); and Bohringer & Sohne, Ingelheim-am-Rhein, amongst others. Rye-sour starters, contain lactic acid bacteria and yeasts existing in symbiosis. The lactobacilli are classified as either homofermentative or heterofermentative, according to their enzyme systems. The homo fermentative species ferment glucose by the fructose disphosphate pathway, converting it with a 90% lactic acid yield. The heterofermentative species ferment it over the hexose monophosphate route, yielding about 50% lactic acid, carbon dioxide, ethanol, acetic acid, and other organic acids. An average starter composition is homofermentative lactobacilli 54%, and heterofermentative lactobacilli 46%. The most significant strains internationally are: L. brevis, L.fermentum, L. plantarum, and L. casei. The most significant yeast strains found in starter cultures are: S. cerevisiae, Pichia saitoi, Candida krussei, and Torulopsis holmii. The composition and amount of starter-culture used will determine the sour-dough ripening-time. The ripening- or maturing-time ofthe sour-dough always depends on the rhythm of the growth curve of the microflora, i.e. cell-count v. time (hours). During the first 2 hours, a doubling of the cell-count (generation-time) takes place owing to exponential reproduction. At about 4 hours, the state of exponential reproduction lapses into stagnation, equilibrium existing between newly formed cells and dying cells. This coincides with optimum maturity, detected by measuring acidity-index, pH, gas-development, and cell-count. An experienced baker can detect maturity from the aroma, and cracks which appear in the flour-strewn top surface of the sour-dough. In practice, the baker coordinates the controllable variables to optimize the chosen technological process. Controllable process variables include, temperature, standing-time, dough consistency (dough yield), type and amount of flour added at each process-stage (dough substrate nutrients, i.e. reproductive-factor or Vermehrungsfaktor to the German baker), aeration, and amount of initial starter-culture used (Anstellgut to the German baker). Sour-dough processes can either be discontinuous (batch), or continuous, the number of process-stages involved showing some variation from bakery to bakery. At each sour-dough stage, appropriate control variables are chosen to favour either lactobacilli or yeasts. Thus ensuring an optimal balance of yeast and bacteria at the final doughmaking stage. The three-stage discontinuous or batch sour-dough process, often used in small to medium sized bakeries, involves the preparation of initial (Anfrischsauer), basic (Grundsauer), and full (Vollsauer) sours before the final dough stage. The basic-sour stage is stood overnight for 4-8 hours at 22-28°C, with a dough-yield of 145-160%. This stage is utilized to propagate the lactobacilli, and so intensify acid and aroma build-up, thus suppressing the sour-dough yeasts. By scaling up the quantities of each stage accordingly, enough basic-sour can be produced for four full-sours on reaching maturity. These, in turn will produce four final doughs at maturity. The basic-sour is self-preserving, when the acidity-index reaches about 20 (approximately 2% acid concentration), owing to lactobacilli activity-stagnation but retention of vitality. Therefore, the basic-sour stage can be not only perpetuated from day to day, but also stored over the week-end or for a whole week's production. This can, however, only be done by preparing a basic-sour of firm consistency (dough-yield 150, or 2 parts flour to I part water). Following this procedure, the aroma-strength and preservation capacity of the basic-sour allows it to be utilized as a flavour concentrate, adding it at 5-15% of total flour weight depending on the type of bread required. Leavening is supplemented by the 754 Handbook of breadmaking technology

addition of yeast. However, the orthodox procedure is to proceed from basic-sour to full-sour by adding a further 32-35% of total rye-flour content, and 55-60% more water. Adjusting the dough yield to 180--200%, and the temperature to 30--32°C, allowing a ripening-time of 2-4 hours. These conditions favour the production of both lactic and acetic acids, as well as activating the yeasts. This influences both bread-crumb properties and flavour later. The final dough is prepared by adding 48-52% of total rye/wheat-flour, and 40--45% water with 1·6- 1·8% salt (total flour weight), the final dough-yield being adjusted back to 145-160%. Final dough temperature is set at 28-32°C. Mixing times are 20minutes for conventional mixers, and 6 and 2 minutes for high-speed and intensive mixers respectively. In the case of rye-meals mixing times of 30minutes (conventional), and 20minutes (high-speed/intensive) are appropriate. Starting from scratch, this typical three-stage system would require the preparation of a starter-sour by mixing 0-5% total flour weight of dry starter with 1-2% of total flour, and 2-3% of water, which is then added to the initial-sour as 'seed'. The percentage of total rye-flour which has been subjected to the souring process is an important technological parameter for each type of bread, valid guidelines are the following: 100% rye• flour bread 40--50%; mixed rye/wheat bread 40--60%; and mixed wheat/rye bread 50--100%. This ensures bread quality and flavour intensity. The quasi-continuous sour-dough process, although prepared on a discontinuous (batch) basis, is regarded as being continuous since part of the mature full-sour is used to prepare a fresh initial-sour, thus perpetuating the sour-dough preparation and maturing system. The KVT 1000, 1500 and 1800 are examples of plants using this system. The process is perpetuated from one mature full-sour to another, two-thirds of the mature-sour being used to prepare the final dough, and the residual one-third used to prepare the fresh initial-sour. The full-sour dough• yield in this process is 230% at 28-29°C, requiring a ripening- or maturation-time of 3·5 to 5·0 hours. The full-sours are mixed, and then allowed to mature in segmented compartments of a carousel-bunker. After degassing, they are mixed into a final dough using a continuous• aggregate, from which extrusion takes place. Since this system is routinely used for the production of mixed rye/wheat doughs, wheat- and rye-flour, water, salt solution, and the mature full-sour are fed into the mixing-aggregate. The Isernhiiger sour-dough process provides sour-dough of constant quality, and in the required quantity on a flexible basis, to satisfy the demands of the essentially craft-operated bakery. This patented process gives a pumpable product, which can be integrated into a modern computer-controlled doughmaking system, and which can be stored lind still give reproducible bread quality for a day's production. Simultaneously, this patent allows the processing of stale-bread paste, which improves crumb-elasticity and avoids wastage. The Berliner short sour-dough process propagates the heterofermentative lactobacilli by using a dough-yield of180--200% and a temperature of 35°C, which gives an adequate acidity• index of 10--13 -within a maturing-time of 3 hours. This gives the favourable ratio of acetic acid to lactic acid 30:70, but some loss of crumb properties could present itself. Quality L'ye-bread,preparation demands a uniform control over the sour-dough processing• stages, and the elimination of external influences. The diverse types of sour-dough processes confront the microorganisms with specific conditions, which control their metabolic output, and result in differences in both dough acidity-indices and pH. The type and species of the lactobacilli are typical for each process. The relative amounts of lactic and acetic acids produced by fermentation can be influenced by the sour-dough temperature; even the ratio of D- to L-Iactic acid can be influenced by the choice oflactobacilli. Control of dough-yield (and consistency), also influence the acid build-up from the various types of bacteria used, e.g. L. casei and L. brevis var. lindneri. In addition, the total microflora content of the starter-culture influences the quality of the sour-dough in which it is used. The lactobacilli exist in symbiosis with the various yeast types and strains, benefiting from the proteolytic activity of the latter. Without a complete knowledge of the sour-dough microflora, and the exact understanding of their mode of growth, and the factors which influence them, any changes in process Noles and references 755 parameters cannot be correlated with their effects on sour-dough quality. Starter-cultures for rye and rye/wheat flour breads can contain the following microorganisms: L. brevis var. lindneri, L. brevis, L.fructivorans, L. plantarum, and L.farciminis, amongst others. The prime function of which is to lower the dough pH, and produce a balanced ratio of lactic to acetic acids, referred to as the 'fermentation-quotient'. Maturing-times vary considerably between 2 and 5 hours, with the exception of overnight, or longer term basic-sours made with a firmer consistency with more flour to slow down the microbial activity, and excess souring. Standing times are the prime consideration in practice, and such process variables as: temperature, dough-yield (consistency), starter-culture concentration, reproductive-factor, and rye-flour type are adapted and adjusted accordingly. More bread-faults result from immature doughs than over-ripe ones, the latter sour-dough situation being capable of correction by the addition of appropriate amounts of potassium carbonate. Rye-flour quality shows wide variations due to climatic conditions during growth and at the time of harvest, as well as post-harvest treatment and storage. However, contrary to common belief, rye quality is often more influenced by deficiencies in the degree of polymerization of the grain storage materials, than by actual increases in enzymic activity. In many cases, rye• flour deliveries with Falling-number (Hagberg-Perten) values less than 100 show quite satisfactory or even good processing properties. However, values in excess of 150, but not over 220 will provide better tolerance to a wider process range. Amylogram viscosity at the maximum gelatinization temperature should be over 300 units, at a temperature of at least 64°C, gelatinization commencing at about 53°C. Rye wholemeal samples should be at least 150 Falling-number to produce flours of adequate tolerance. These values are based on wholemeal and flour sample weights of 9 g/25 ml water, v. 7 g/25 ml for wheat samples. Amylogram values are based on 80 g/450 ml water. Rye-flour water absorptions, measured at 350 Farinograph units, range from about 64% to 73%, depending on crop-year and extraction rate. Any reduction in flour water absorption suggests less swelling capacity initially, but this is normally realized during the sour-dough stages. Test dough yields of 168% (based on total flour weight 100 parts), with dough consistency about 325 Farinograph units, should give bread volumes of 520-550 ml/250 g. Loaf-symmetry (width and height measure), and sensory evaluation of crust/crumb structure, colour and flavour, are most important attributes for all rye breads. The loaf width: height ratio should be ideally 1'5-1·6, with little tendency to dough flow-out. The multi-stage processing of rye-flour doughs, allows the optimization of the process for diverse bread varieties, using rye-flour of variable characteristics. By using a batch process, and various process-stages of appropriate temperatures, consistencies, standing-times, and reproductive-factors to suit the microorganisms, large quantities of dough can be leavened and acidified with a relatively small quantity of starter-culture (Anstellgut). Processing objectives are: sour-dough yeast reproduction; bacterial reproduction; inhibition of wild microflora; achievement of optimal pH and acidity-index; and controlled swelling of the flour hydrocolloid components. Process control is effected by precise fixation of temperature, weight, and time. A facility for testing the sour-dough acidity-index at each stage is desirable for consistent bread quality. Many bakeries no longer use multi-stage processes, but in so doing compromises have to be made. The basic-sour, or basic-sour without full-sour is an example of a rationalized batch process schedule for the production of rye breads. This is achieved by separation and specialization of the functions of the various sour-dough stages of multi-stage procedures. The basic-sour being utilized to produce the aroma substances, and natural acidification, any deficiency in acidity being supplemented by the addition of dough-acidulants containing lactic, citric or adipic acids. Deficiencies in leavening effect are supplemented by the addition of baker's yeast at the 0·8 to 1·5% (flour-weight) level. Initially, a basic-sour is prepared with an amount of starter-culture depending on the desired standing-time, i.e. 5% to 50% of total rye-flour 756 Handbook of breadmaking technology content. Using 50% starter, the basic-sour matures in about 4 to 6 hours. The use of 500 g starter/tO kg flour (5·0%) in the sour, adjusting dough yield to 150% (2 kg rye-flour/litre water) and maintaining dough temperature at 24°C, should give a basic-sour of pure aroma and flavour over 11-12 hours. The temperature latitude being 20--30°C for acid-formation and fermentation. Once enough mature basic-sour has been produced, the process is progressively continued from one basic-sour to the next in one stage. For quasi-continuous production, two-thirds mature basic-sour are processed into the final dough, and the residual one-third is used to prepare the next basic-sour. For convenience, salt is added as a 25% solution, and up to about 3% of stale-bread crumb (flour weight), finely milled and soaked in water at 24°C, can be added to the final dough. The Berliner short sour-dough process, can reach maturity within 3 hours, the hetero• fermentative bacteria producing an acidity-index of 10--13. This is achieved by using a flour content five times that in the starter-culture (reproductive-factor), dough yield being set at 180% to 200%, and sour-dough temperature 35°C. As a general guideline, at least 50% of total rye-flour content of rye/wheat doughs should be subjected to the sour-dough process. KVT 1500 continuous doughmaking plant (CSSR) Dough-preparation rates and feed-rates. Source: Special Bakery Processes by Werner Schwate and Udo Ulrich, VEB-Fachbuchverlag, Leipzig, GDR, 2nd edn, 1986, p.38. Progres!\ively produced rye-sour for continuous automated production of rye bread varieties is the subject of a patented system of joint design and construction by the Vereinigte Nahrungsmittelindustrie (VNI) in Vienna, and Reimelt of FrankfUrt, FRG. Foramitti, A. (1982) Getreide Mehl und Brot, 2, p.47-50 (German). In the USSR sour-doughs/or rye breads are either made with firm consistency sours (Golowka), involving a four-stage build-up, or a softer sour (Kwass). The golowka production cycle can be shortened by working from full-sour to full-sour, on a quasi-continuous basis. The water content of the golowka full-sour being 50%, i.e. a sour-dough yield of 150%. In this case it becomes a two-stage process: full-sour and final dough. Using a batch system, the mature golowka full-sour can be divided into 3-4 parts. One part being mixed with more flour and water to prepare more golowka, and the residual 2 or 3 parts used to prepare 2 or 3 portions of dough. The build-up of the softer sour or kwass involves three stages, and the water content of the resulting mature full-sour is on average 2'0% higher than the golowka full-sour. On a batch system, two-thirds of the mature kwass full-sour is used to prepare the dough, and the residual one-third used to prepare a new batch of kwass full-sour. In some bakeries much higher levels of water are added to the full-sours to adjust flavour, and facilitate its transport through pipelines. Also the amounts of mature full-sour used to prepare doughs will be varied to suit production conditions, such as: ambient temperatures,golowka or kwass activity, flour quality, and production-stoppages. The S-1liquid-sour process, due to E. K. Gladkova and co-workers, utilizes a lower viscosity sour, containing so-called beta-bacteria, pure cultures of group B lactic acid bacteria (Seliber classification). These heterofermentative types produce many volatile flavour acids in addition to lactic acid, alcohol and carbon dioxide. By using selected strains of these bacteria, with a reproduction temperature optimum of 25-30°C, 50% of the mature sour is used for dough preparation, and the residual 50% supplemented with the following nutrients: 40% of a saccharified, pregelatinized flour/water suspension (PFWS), prepared by heating a 1:3 or 1:2 flour/water mixture for 2-4 hours at a constant 62-65°C, 51 % water and 9% flour. This enriched sour is fermented at 33-35°C for 60--75 minutes, the sour reaching an acidity-index 8-11. Then, 50% of this mature sour is utilized to prepare a fresh sour. Sours are prepared in stationary batch containers. To prepare the final dough, 50% sour (based on flour weight), and the requisite amount of flour, water and salt-solution are adequately mixed. The dough is set at 34-35°C, and bulk-fermented for 120--140minutes. A 100% rye wholemeal dough would attain an acidity-index of 8,5-9,0. The doughmaking aggregate ChTR of the I. L. Noles and references 757

Rabinowitsch system is often utilized in Soviet bakeries for this purpose. For processing the golowka (firm consistency sours), the bunker-type system ofN. P. Gatilin became widely used during the 1960s. This involved the use of one bunker-aggregate for preparation of the full• sours, and another for the final doughs. About one-third of a mature full-sour being fed back into the sour-dough mixer aggregate to inoculate the fresh sour. Stationary bunker-systems, such as that of A. M. Chrenow can also be utilized for both sour-dough and final dough preparation, and by placement of a rotary sectioned-bunker aggregate between them, a quasi• continuous doughmaking system can be constructed. The sectioned-bunker is used for sour• dough or sponge (wheat-flour) maturation. For continuous rye dough preparation, using liquid-sours of the kwass or S-1 type described, a Ch-12 mixing-aggregate, coupled with a sloping trough-shaped fermentation-conveyor ChTR (as used in the Rabinowitsch system), is utilized. This being also applicable to wheat-flour doughs, where indirect pre-ferment systems are in use. The various aggregates mentioned are illustrated in Section 1.7. Rye bread/aulls can be categorized into: flavour deficiencies; poor loaf symmetry; and poor crumb-elasticity, after 24 hours setting and cooling. Rye-flour delivery quality profiles with standard Falling-number (9 g/25 ml water) values within the range 90 to 110 must be regarded as suspect for processing without appropriate corrective measures. A retest using water acidified to pH 4·0 with dilute lactic acid will provide supplementary information, since such flours often respond positively to enzymic inhibition adjustments, and produce quite acceptable bread when correctly soured. Test-bakes are carried out using both lactic and acetic acid solutions, and mature biologically produced sour-dough. Other corrective measures which can be superimposed on a pH adjustment include the use of one of the following hydrocolloids: Quellmehll-3%, CMC 0·5%, and xanthane gum 0·2-0·5%, all based on flour weight. These substances regulate the dough water absorption and its distribution, when flour component polymerization is deficient due to rye growth conditions in the field. Simultaneous addition of one of the following emulsifiers, calcium stearoyllactylate, sodium stearoyllactylate, DATEM, or mono- and diglycerides, at the 0·5% flour weight level, exerts a synergistic effect on hydrocolloid function. The other rye• flour quality profile-extreme results from a highly polymerized grain structure, which shows resistance to enzymic breakdown. Such flour samples have standard Falling-number values of 250 to 300, and Amylogram gelatinization-maxima of 700 or more. When processed into bread without corrective measures, the baked loaf shows a close, cracked crumb, with poor volume, which stales rapidly. This is due to the hard, intact starch structure, and insufficient amylosis, and can be corrected either by blending with a smaller percentage of sprouted rye• flour, or by the use of corrective additives. Appropriate corrective additives are malt-flour at 0·1 %, stale bread-crumb paste at up to 5·0%; or it is possible to prepare a 'scald' (pregelatinate) of about 5% of the flour, treating 1 part flour with 1 part boiling water. Optimum concentrations of bacterial and fungal amylases, proteinases, and pentosanases, can also have the desired effect, but correct treatment levels must be determined with the help of Amylograph standard and swelling-curves.

CHAPTER 2.5 FORMULATION AND PROCESSING TECHNIQUES FOR SPECIALTY-BREADS

This sector of the bread market has shown promising growth in most countries during the 1970 and 1980 decades, and in some countries growth was already under way during the 1960s. In general, the greatest demand has been for whole grain and meal/grit-containing bread varieties. In traditional white-bread consuming countries such as the UK, continental• style rye and other cereal- and seed-containing breads have shown growth rates exceeding 300% between 1986 and 1989. The innovative potential for the British baker to market an improved variety of high-quality continental breads remains very considerable. From the 758 Handbook of breadmaking technology

regulatory viewpoint, a specialty-bread can contain rye and/or wheatmeals and/or certain specialty-flour products (often differing in the method of preparation from normal procedures), containing specific raw materials (often in the form of a premixed concentrate), which change the nutritional value and/or flavour of the bread when compared with basic bread varieties. The interpretation of such regulations, however, will depend on the country. For example, in 'black-bread' consuming countries such as: GDR, FRG, Austria, Czechoslovakia, Hungary, Poland and the USSR, basic bread varieties may already contain 50% or more rye-flour or rye-meal. Specialty-breadformulation, particularly when yeast leavened, often requires the addition of suitable processing aids and/or a formula rebalance. Typical processing aids in the form of raw materials are: vital gluten, sugar in solid or liquid form, salt and shortening, which can effect a rebalance. Typical dough-conditioners are: stearoyl-2-lactylates, ethoxylated monoglycerides, and other emulsifier-type additives, depending on local legislation. Multi-grain or mixed-grain breads, require a 'soak-stage' to effect complete swelling of grain components. The grits, meals or other cereal flours are blended together to form a mash with most of the water, and allowed to stand for 6 to 8 hours. The increasing demand for wholegrain bread varieties is due to nutritionalists generally recommending the consumer to concentrate on fibre-rich menus. Specialization categories for formulation include: fibre-rich, protein-enrichment, caIcium• enrichment, salt-reduced, and special formulations for dietetic consumers.

Multi-cereal breads can be formulated by substitution of 5~30% wheat-flour by mixtures of rye-, corn-, oat- and barley-flours, with the addition of vital-gluten to provide the structure. High-jibre breads containing the fibre fraction not enzymically degraded within the human digestive system, i.e. cellulose, lignin, hemicelluloses, pectins, gums and other non-starch carbohydrates not digested by man (loosely referred to as 'crude-fibre'), are formulated with such raw materials as: wheat-bran, corn-bran, soy-bran, oat-hulls, rice-bran, and powdered cellulose. In fact, the so-called 'crude-fibre residue' is made up of about 97% cellulose and lignin, 13% to 70% of which is actual 'dietary-fibre'. The range of dietary-fibre contents of the above raw material sources is about 45% (rice-bran) to 99·5% for powdered cellulose (insoluble dietary-fibre). Insoluble-fibre is defined as including cell uloses and lignins, and some hemicelluloses. Soluble-fibre comprises pectins, gums, pentosans, and some hemicelluloses, which has physiological significance in the control of cholesterol and diabetes. Total dietary-fibre (TDF) consists of both soluble and insoluble fibre, and is determined by the A.O.A.c. Prosky-TDF procedure, which is an enzymic digestion intended to simulate human digestion. Other sources of fibre include: spent brewer's grains ('mash') or' M alztreber' (German), and washed orange-pulp (TDF 46'5%, insoluble dietary-fibre 21·9% and soluble• fibre 24'6%). Roasted commercial fibre sources, e.g. oat-fibre, corn-fibre, and soy-fibre, contain significant amounts of both insoluble and soluble dietary-fibre, compared with raw milled-products. Formulations containing more than 10% added fibre require a high-protein, gluten-rich flour (16% protein), and 60~70% of the flour should be used in a sponge-stage. Where 10--20% added fibre is used, water absorption must be increased in excess of 100% to ensure complete hydration of the gluten proteins, and the added fibre. In this case, 6~ 10% vital-gluten is necessary to provide an acceptable cell-structure, about 5% of which is best added to a sponge-and-dough process procedure. Yeast levels should be increased to 3~5%, 1~2% retained for the dough stage. A salt adjustment of up to about 3%, and the addition of high-fructose corn-syrup at 8~ 12% should provide an adequate rebalance. Honey or molasses can replace part of the sugar where wheat-fibre is utilized. Shortening additions should be avoided on calorific grounds, but sodium stearoyl-2-lactylate, added at 0·5% does improve bread volume. Mould-inhibitors usually become necessary, owing to higher bread moisture levels. Since fibre is inert in terms of energy contribution (calories), some sources can be utilized for the formulation of low-calorie yeasted breads. In 1984, the FDA in the USA, Notes and references 759

allowed the exclusion of non-digestible dietary-fibre when calculating the calorie content of reduced calorie foods. Therefore, for every 1·0% of total dietary fibre added, the product calorie content declaration can be reduced by 4 units/tOO g. Calories/tOO g are calculated as being equal to four times the protein percentage, plus nine times the fat percentage, and four times the percentage total carbohydrates, minus the percentage of total non-digestible dietary-fibre. High-protein breads This can be achieved by using a diverse source of high-protein raw materials such as: full-fat soy-flours, groundnut protein isolates, soy protein isolates, cottonseed protein, gluten-flour, vital-gluten, milk protein fractions, and composite mixtures of these to form premix concentrates. To obtain satisfactory results, a sugar rebalance is desirable, and an optimal level of potassium bromate or ascorbic acid, if the former is not permitted. The additional use of a dough-conditioner, such as 0·5% sodium stearoyl-2-lactylate, will give an even better end-product. Improved results are also obtained with selected surfactants of the sucro- or glycolipid type, and first preparing a sponge, to which is added on maturity the 10-12% soy• flour in paste form at the doughmaking stage. In countries where rye-flours as well as wheat• flours are used for basic bread varieties, the same general regulations for specialty-breads (Spezialbrote) apply. However, many other milled-products and special fractions are utilized, e.g. oats, barley, maize, and their mill-stream (passage) products, grain-germs, outer layers and brans. Other raw materials of vegetable origin are: fruit and vegetable products, spices, oil-bearing seeds (sunflower, linseed, cottonseed, etc.), buckwheat, sesame-seed and carob• bean flour. Those of animal origin include: milk and milk-products, and meat and meat• products, such as full-milk powder, whey, buttermilk, whole-egg powder and butter. Certain partially cooked extruded cereal products also find application. Many of these materials increase bread yield, e.g. vital-gluten, potato-semolina (flour), and soy-based products. In developed countries, the need for protein-enrichment is limited, the only case being to supplement the lysine deficiency of wheat flours. More urgent requirements are for increased dietary-fibre, reduced fat and sodium intake. There may also be a case for iodized potassium, iron, selenium and other trace elements in certain countries. Specialty-breads, containing larger amounts of whole-grain material, binding increased amounts of water, represent an economy in raw material, compared with the basic breads made with lower extraction products. Total specialty-bread consumption in the GDR, including dietary-breads, amounts to about to%, which is mainly produced in the industrial-bakeries, but the potential for craft• bakeries remains open. Schneell'eiss, R., and Heinrich, G. (1984) Biicker und Konditor, 5, p. 132 (German). In the GDR, raw materials are selected which best serve the nation's dietary requirements. Current analysis indicates that specialty-breads with fibre-enrichment are not yet being consumed on a broad enough basis, especially as a regular part of the diet. Many consumers who are dependent on various medications, could instead use a basic food to alleviate their problems. In the above-cited report, entitled 'Specialty-breads-a requirement from the baking industry', the authors state that the required shelf-life of such breads is about 7 days, and that they should ideally attain their peak flavour acceptability after 48-72 hours. When sliced and wrapped, 250 g and 500 g units show a prolonged shelf-life of up to 9 days, when made from rye and wheat wholemeal flours, compared with only 4 days when they contain rye-flour type 997 and patent wheat-flour type 550. Some well-known specialty-breads from the GDR are Mecklenburger Landbrot, and Malfa-Krafima-Brot. Mecklenburger Landrot, can be produced either discontinuously or continuously, using a sour-dough process. However, continuous production requires long runs with the ryemeal processed in the sour. On a discontinuous basis, enough basic-sour is prepared for the maturation of two full-sour batches, the basic-sour standing for 5 hours at 25-27°C. The full• sour matures for 2 hours at 28-30°C, having been enriched with whole rye-flour. The final dough consisting of the mature full-sour, a blend of whole rye-flour, rye-flour type 997, and 760 Handbook of breadmaking technology wheat-flour type 550, yeast, salt, caraway-seed (milled), sugar, caramel colour and water to give a dough temperature of 30°C. Final proof is at 32-34°c for 40-50 minutes for units scaled at 1150 g. Baking is set at 280°C initially, falling to 200°C at the outlet for a period of 50 minutes. Heinrich, G., and Schneeweiss, R. (1984) Backer und Konditor, 5, p. 143. Recipes and pro• duction methods for specialty breads-Part I (German). Mecklenburger Landbrot was sold as 1000 g loaves at 0·85 MDM (fixed price), which is equivalent to 30p at 1989 exchange-rates (based on a DM:MDM exchange-rate of 1:1). The baking-loss allowed for is 13% for Mecklenburger Landbrot. Malfa-Kraftma Brot, is a long-established specialty-bread in the GDR, containing 10% Kraftma special-flour, prepared from malted barley, thus giving the bread a malt-aroma and dark crumb-colour. It can be produced either as a hearth (oven-bottom), or panned bread weighing 1 kg, and continuous plant can be utilized for both sours and final doughs. In this case, dough-yields must be controlled. The basic-sour is prepared from rye-flour type 997 instead of coarse rye-meal, including the appropriate amount of starter-culture and water. The temperature of the sour is set at 26-28°c, and allowed to stand for 6-7 hours. On reaching maturity, the full-sour is prepared by enrichment of the mature basic-sour with more rye-flour type 997 and water. This is set at 28-30°c, and stood for 2,5-3,0 hours for maturity. The final dough is then made up of the mature full-sour, and a blend of rye-flour type 997, wheat-flour type 550, and Kraftma special-flour, salt and water to give a dough temperature of 29-31 0c. This receives a floor-time of 15-25 minutes. Final-proof is for 35-45 minutes at 32-34°c for units scaled at 1150 g. Baking temperatures are set at 250-270°c initially, falling to 220 and 180°C, the baking-time for hearth bread being 45-50 minutes, and 60-70 minutes for panned-bread. As with all coarse-textured cereal meals and flours, the Malfa-Kraftma special bread-flour is best mixed with water, and allowed to swell before addition to the dough. Trendbrot and Driftbrot, are GDR specialty-breads enriched with dietary fibre, made from rye-flour 997, gluten-rich wheat-flour, wheat-bran, and Telavit-trend concentrate. A Full• sour is prepared from a mature basic-sour, enriched with rye-flour 997 and water to stand for 2-2'5 hours at 28-30°C. The final-dough is made by the addition of gluten-rich wheat-flour, wheat-bran, yeast, salt, Telavit-trend concentrate, an emulsion and water. The dough is given a floor-time of 20-30 minutes, scaled at 1160 g per unit, and then given a final-proof of 30- 40 minutes at 32-35°C and RH 80-90%. Baking is at an initial temperature of 280°C, falling to 21O°c for at least 70minutes. Driftbrot, in contrast to low extraction wheat-bread, has a reduced energy or calorific value. Instead, it has a high protein and dietary-fibre content, especially suitable for overweight subjects, by preventing the formation of excess adipose tissue. It is prepared by a direct or straight dough procedure, but the rye-flour should be added in a soured form, having undergone a three-stage souring process to the mature full-sour stage. The mature full-sour is added to the final dough, which is made up of the following materials: gluten-rich wheat• flour, special drift flour, yeast, salt, and an emulsifier in paste form. The dough receives a f1oor• time of 60 minutes, with a punch or remix at 20-minute intervals. For 1500 kg baked unit weight, the baking-time must be at least 80 minutes, at an initial temperature of 280°C, falling to 210°C with steam injection. Hagenower Spezialbrot, is a light-eating bread containing both whey and whole-egg powder, which gives it a mild taste and tender crumb. It is produced as a hearth-loaf of 1 kg or 1·5 kg baked weight. A sponge is prepared with gluten-rich wheat-flour, yeast, whey, whole-egg powder and water, to stand 60-90 minutes at 26-28°C. The final dough is made by adding the mature sponge and a portion of mature basic-sour to rye-flour 997, more gluten-rich wheat• flour, more yeast, salt, a small amount of prepared dry-sour and water. The dough is given a floor-time of 15-25 minutes at 28-30°c, scaling at 1680 g for a l'5-kg loaf, and 1150 g for a I-kg loaf. Final-proof is for 40-50 minutes, baking the 1·5 kg units for 60 minutes, and the Noles and references 761

I-kg units for 50 minutes. Baking-temperatures commencing at about 270°C, falling to 180°C. Heinrich, G., and Schneeweiss, R. (1984) Backer und Konditor, 6, p.175. Recipes and production methods for specialty-breads II (German). The floor-time should not be exceeded, otherwise the characteristic aroma is lost. Pumpernickel is an old-established specialty-bread made from rye-wholemeal, salt and water, using a sour-dough or Quellstiick, which means soaking part of the rye-meal. Yeast at 0·3- 0·5% and up to 3% sweeteners can also be added. Baking-time must be at least 16 hours, at about 100°C in a chamber saturated with steam. The baked bread has a dark, dense crumb. About 25% of the rye-meal is made into a sour-dough, applying the traditional three-stage process, another 25% of rye-meal being used to prepare a 'Quellstiick' with warm water, and allowed to stand to swell for about 7 hours at 22°C. On reaching maturity, both the sour• dough and Quellstiick are added to the residual 50% rye-meal, more water, salt and yeast. The final dough-yield is adjusted to 160%, with intensive mixing. The dough-pieces are then worked-off by depositing them into baking-pans; or they can be processed in one elongated dough-strip, divided into sections. Proof-time is 50-60 minutes with exact relative humidity control. Baking must be carried out with steam-saturation, either in a special baking• chamber, or in a standard oven providing adequate steam-saturation. Baking-temperatures are maintained at 100°C for at least 16hours, under a saturated-steam atmosphere. A simplified American-style pumpernickel is made from a Briihstiick/sponge with clear flour, dark rye-flour, yeast and water, being set at 24°C for 3 hours. The final dough is then made by the addition of ryemeal, sour-dough, salt and water. Additionally, malt, sweeteners and shortening are used at 1·0% flour weight. The final dough is set at 27°C, scaled, rounded, and rested for 15 minutes before final-shaping. Final-proof requires 50 minutes with humidity control, baking at 220°C, in saturated-steam. Ponte, J. G. Jr. In Production Technology of Variety Breads, edited by B. S. Miller, AACC, St. Paul, MN, USA, 1981. Wheat and rye wholemeal products for bread processing are best prepared by roller-milling as opposed to the use of hammer-milling. Zwingelberg, H., Seibel, w., and Stephan, H. (1984) Getreide Mehl und Brot, 38, 3, p.69-76. Influence of milling wheat and rye wholemeals on their baking-performance (German). Seibel, w., Stephan, H., and Zwingelberg, H. (1984) Getreide Mehl und Brot, 38,11, p. 339-45. The manufacture of whole-grain-meal alternative breads (German). The above researchers established that the mode of grinding/milling of wheat and rye into wholemeals had a great influence on the specific weight (g/litre), as well as the relative kerneI• hardness of the grain from which it is ground/milled. The roller-milled products are lighter in weight for the same volume than the corresponding hammer-milled products. In general, the softer kernel structured grains give lower g/Iitre (lighter) meals than the harder grains. These workers also developed certain suitable dough-processing methods involving a two-stage sour-dough for wheat or rye wholemeal bread, as well as the application of both the Berliner and Detmold one-stage sour-dough processes, and the SEKOWA special ferment method. For the two-stage process, to achieve a mild souring, only 0·1 % starter, based on total meal for souring, is necessary. If stronger souring is required, up to 10% of the total meal for souring can be added. The first sour-dough stage for a 10 kg wholemeal dough requires 250 g wholemeal (fine), 1 g starter, 500 ml water, which gives a dough-yield of 300%. This is allowed to stand at 24-26°C for 15-20 hours. To the mature first-stage sour (750 g) is added a further 750 g of wholemeal and 1500 g (ml) of water. This is equivalent to a dough-yield of 300%, being allowed to stand for 3 hours at 26-28°C. The final dough is prepared by adding 9000 g of wholemeal (fine) to the 3000 g of mature second sour-dough stage, 120 g of salt, and approximately 5000 g water for wheat wholemeal dough or 5500 g for a rye wholemeal dough. Respective yields being 170% and 175% of final dough. Final-dough proofis at 40-45°C for 762 Handbook of breadmaking technplogy

6~90 minutes. The SEKOWA special ferment procedure utilizes a three-stage sour, using a total of 0·05% of the special ferment, which contains hetero- and homofermentative lactobacilli, and yeasts cultured under wild and natural conditions. The first stage consists of 100 g of wholemeal, 100 g wheat-flour type 550, 20 g special ferment and 220 g water for a 10 kg wholemeal batch, giving a dough-yield of210%. This is allowed to mature for 24 hours at 26-30°C. The second stage is made up of the 400 g of mature first sour, 300 g wholemeal, and 100 gwater, adjusting to a dough-yield of 160%. This stage matures for a further 24 hours at 26-30°C. On reaching maturity, only 100 g of the 800 g total of this material is used to make the final dough. The residual 700 g is placed in a cold-room for further batches, being stable for several months. 100 g is appropriate for 10 kg of wholemeal. The pre-ferment is 100 g of mature second-stage sour, 30 g of SEKOWA special ferment, 3·5 kg wholemeal, and 3·5 kg water. This adjusts the dough-yield to 200. This pre-ferment is allowed to mature for a further 24 hours at 26-30°C, yielding a total pre-ferment weight of 7·130 kg. The final-dough is then made up of about 7·000 kg of mature pre-ferment, 6·500 kg wholemeal, 150 kg salt, and 3·500 to 4·000 kg water, giving a dough-yield of17~175%. This is allowed 45 minutes at 30°C. The scaled dough-pieces are then final-proofed for 6~90 minutes at 35--40 minutes. Whole-grain bread, containing whole grains, whole crushed grains or very coarse meals or grits, are becoming a favourite specialty-bread with the consumer. Typical characteristics of whole-grain specialty-breads are: a soft crumb; good keeping-properties; moist crumb, but no signs of dough-like structure; mild, slightly sour taste; good slicing properties. The grain• kernels added to the dough must be readily masticated, and have good digestibility, but be clearly visible on slicing. The baking procedure for this type of bread containing whole rye grains can be one of the following:

~in a steam-chamber as panned bread, with or without a sour-dough stage; ~in a conventional oven as panned bread made with sour-dough either as sliced and wrapped portions or whole loaves; ~in a conventional oven as hearth-bread (oven-bottom) dispatched in the form of a whole lo~ . Irrespective of the baking procedure, the grains must be allowed to swell beforehand, since the amount of water added during sour or dough preparation is not adequate, and the time• interval from doughmaking to baking inadequate for proper grain swelling. The pretreatment of the whole or crushed grains is carried out in the form of a soaking in water between 70 and 100°C (Brilhstilck), or by a lower temperature soak (Quellstilck) at 15 to 70°C. The Quellstilck is preferable owing to ease of preparation. Possible variations in baked• products include: whole-grain panned bread with 50% of the milled product as rolled rye grains; light whole-grain containing 25% rolled rye grains; dark whole-grain containing 25% rolled rye grains. The preparation of the Quellstilck can be rationalized for quasi-continuous production and processing on a bread-line. This is achieved by using a mixer unit with only three mixing-cycles/4 hours, in which is placed the crushed grain, salt and water. After a 4-hour swelling period, the product is drained through a mesh-grill, and added to the mature full-sour in the machine bowl in the desired quantity. After mixing, the dough is processed in the normal manner with a floor-time of 30 minutes, followed by rounding, final-proofing, and baking. The swelling process can be accelerated somewhat by using a dilute solution oflactic or acetic acid instead of just water when preparing the Quellstilck. The use of a mixer to prepare the Quellstilck, avoids the presence of unswollen white kernels in the cut bread. Whole-grain breads represent a considerable efficiency in the nutrition of a nation, owing to the high extraction rate of the grain consumed, and a reduced processing cost for the grain employed. The qualitative value of the end-product is extremely high. Bran-bread with raisins was originally an American specialty, where Californian raisins are considered a health food by the consumer. Before being added to the dough, raisins must be conditioned by soaking in an equal weight of water for at least 4 hours. The raisins can be used as the only source of sweetening, or honey and brown sugar can be added as extra Notes and references 763 sweeteners. Raisins contain an average of 70% sugars, and the amount added can be up to about 18% of the flour weight. A typical bran-bread formulation is the following: high• protein, enriched, first clear flour 80 parts, wheat-bran 20, wheat-gluten 4, yeast 3, salt 2, brown sugar 4, honey 3, shortening 3, dough-conditioner 0-4, water 64. Malted-grain products are particularly useful raw materials for the formulation of specialty• or variety-breads, owing to their high fibre and protein content, as well as the roasted grain flavour and aroma token. The specialty/variety-bread sector of the bread market respresents the greatest potential for expansion and innovation generally. The consumer seeks new taste experiences, whilst insisting on ingredients with a minimum of processing, and a minimum of processing-aids or additives. This is also the trend in food legislation towards the year 2000. Notes and References for Part 3

Chapter 3.1 AIMS AND REQUIREMENTS OF THE BAKING PROCESS

Raw dough-piece undergoes transformation under the influence of heat application to form a light-textured, porous, digestible product of pleasant flavour and aroma. The irreversible structural changes in the dough components involve physical, chemical and biochemical reactions, complex in nature. The reaction rate must be carefully controlled by the amount of heat input, rate of heat-transfer, level of humidity, and time of exposure within the oven chamber. However, this assumes that all 'upstream' process procedures have been optimized to produce a fully mature dough-piece ready for the oven. On setting, the dough-piece undergoes the final phases of swelling and solubilization due to limited heat-transfer. As heat• transfer progresses, gas-expansion and then gas-retention and solidification of the elastic-film surrounding the gas-bubbles take place. The net effect of these developments determine loaf• volume, resulting from dough expansion or 'oven-spring'. Rheological attributes of the proofed dough-piece include elastic-extensibility and tensile• strength, and doughs with a high viscosity/rigidity-modulus ratio, or 'relaxation-time', provide large oven rises. During initial swelling and solubilization, the dough must retain sufficient viscosity and elastic-extension, until the starch can swell and gelatinize, thus contributing to the strength and rigidity of the dough-piece.

Modern industrial baking ovens are designed to convey the dough-pieces on trays or a travelling-band (hearth), through a series of controlled heat-zones, each subjecting the dough• piece to strict conditions of temperature and humidity. For panned-bread, the initial setting temperature would be about 203°C, for a duration of about 7 minutes (about 25% of total baking-time 27 minutes). At this stage the outer crumb layers show temperature increases of on average SOC/minute up to 60-70°C. The dough-surface reaching lOO°C within about 3 minutes, progressively increasing at a rapid rate, reaching about 130°C within 20 minutes of setting. However, heat-transfer to the centre of the crumb proceeds relatively slowly. This is due to the large temperature-gradient of 60-70°C between the dough-surface and the crumb• centre. The heat-transfer proceeds from the outside to the inside, any unbound moisture evaporating in 'evaporation-zones' on attaining a temperature of 100°C or more. This zone then moves with increasing heat-transfer from the outer layers towards the centre. Moisture, on reaching lOO°C evaporates by diffusing through the pores in the crust for the most part, increasing the humidity of the baking-chamber. A smaller amount of steam entrapped within the loaf contributes to the swelling and gelatinization of the dough-layers located near the centre of the loaf. Such processes are linked with heat consumption, and an exact knowledge of heat-transfer mechanism will enable the oven-operator to save energy. Formation of a thin extensible surface-skin, represents the first visual change during the baking process. Temperature/time changes within the dough-piece between 30 and 70°C take place within narrow temperature ranges. At 30 to 40°C, swelling, enzymic activity and yeast growth progress, all fermentable sugars continuing to be fermented by the zymase enzyme-complex, until a temperature of about 60°C is reached. The percentage of starch granules with a damaged outer-layer increases, depending on the interior temperature of the dough-piece during baking. 764 Notes and references 765

Schnee weiss, R. (1965) Report of 2nd Conference 'International Problems of Modern Cereal Processing and Cereal Chemistry', Vol. 2, p. 260. The temperature changes during the baking process and their influence on bread quality (German). Within the temperature range 57 to 79°C, a steep rise in damaged-starch granules (stained by china-blue dye) from 20% to 100% on completion of baking takes place. Schneeweiss, R. (1965) also established that the rate of soluble carbohydrate formation during baking increases rapidly between 43°C and 60°C, from 14·5% up to about 24% after 55 minutes baking-time (hearth-bread). According to Schneeweiss, alpha-amylase enzyme kinetics begin at 30°C, reaching a maximum between 50 and 60"C, beginning to fall off at 70°e. Falunina, S. F. claims that alpha-amylase can remain active up to 7S-S0°C, and that some residual activity remains at 97-9S°e. Even in baked bread, some activity remains at the crumb-centre, providing the crumb pH remains above about 4·3. Falunina, S. F., and Popaditsch, I. A. (1951) DAN (Reports of the USSR Academy of Sciences), 78, 1, 103 (Russian). Falunina, S. F. (1954) MTIPP Report 3, 60 (collective work of Moscow Technological Institute for the Food Industry). Rye-starch starts to gelatinize at 45°C, and becomes complete at about 5SOe. Wheat-starch starts to gelatinize at 55°C, and will continue up to about 65°e. Starch-swelling and gelatinization is made possible by the migration of water from the other dough components to the starch-granule, resulting in partial dehydration of the gluten• complex. This causes the gluten proteins to become more viscous and elastic, before coagulation becomes complete at about 70°C, depending on molecular weight and colloidal state. Yeast-enzyme inactivation occurs between 55 and 60°C, but the zymase-complex remains active up to about 65°e. Oven-spring continues after starch-swelling has begun, due to plastic and elastic dough expansion, but terminates during gluten coagulation. Dough structural rigidity, due to protein coagulation and partial starch gelatinization, takes place between 62 and 67°C, as heat-transfer proceeds. Temperature data cited assume events taking place zonally within the dough-piece at the temperature specified or range cited. At which point in time the various layers attain these temperatures will depend on the efficiency of the heat-transfer system from heat-source to each layer or zone of the dough-piece. Alpha- and beta-amylase act on the gelatinizing starch within the crumb of the dough-piece, increasing the water-soluble fraction. Its extent is both crucial and variable, depending on enzyme kinetics and degree of polymerization of the native starch in the flour used. Both heat-transfer, and dough pH also exert an influence on the speed of liquefaction. Pentosans and hexosans, derived from the cellulosic flour components, are also present in the water-soluble dough fraction. Their content varying from about 0·4% to 1·2% of crumb• weight. These branched-chain compounds are mixtures of xylose, arabinose and glucose, in the approximate ratio 5:4:3. Dextrin content of doughs made from standard flours increase by about 15% during baking, whereas sprouted wheat-flours show increases of 50% or more.

Carbon dioxide liberation is complete at 60 c C, and contributes to dough expansion. With dough-surface skin-drying and thickening, its elasticity is reduced, and crust-browning sets in, at lOO°e. 766 Handbook of breadmaking technology

Oven-spring or loafexpansion, approximating to about one-third of the proofed-loaf volume, takes place at about 100°e. Second and third stages of panned-bread baking amount of approximately 14 minutes, roughly 50% of total baking-time, oven-temperature being held at a constant 240°e. The crumb temperature rises at about 5'5°C per minute during stage two, until it acquires a level of 98 to 99°C at the onset of stage three, after which it reaches a steady-state constant level for the remainder of the baking-process. This level of temperature provides the maximum rate of moisture evaporation, starch gelatinization, and dough protein coagulation. Ethanol evaporates, contributing to leavening, and the loaf interior is transformed into a baked• crumb structure, from its outer layers through to its inner layers, thence to the crumb-centre by heat penetration. On reaching 150 to 206°C, the crust acquires the typical brown colour due to caramelization. Unfermented sugars prior to baking need to be about 2-3% to ensure normal crust formation. Other thermal reactions between sugars and proteins yield melanoid in compounds at 100°C and above. Amino acid, and carbohydrate monomers are the reactants. The dextrins from starch degradation are also involved in non-enzymic browning reactions. Bread-aroma substances are formed at temperatures of 100 to 180°C, parallel with the browning reactions. These are volatile carbonyl compounds (aldehydes and ketones), resulting from Maillard reactions in the crust area. During cooling and storage, these diffuse into adjacent crumb-layers. In dough, bread and oven-volatiles, more than 200 aroma- and flavour-developing substances have been identified. In white bread, volatile organic acids are retained, lactic acid at concentrations of the order of 10-15mg/100g and acetic acid at 2-5 mg/100 g. Rye breads contain much higher levels of these acids, owing to lactic fermentation. Fourth and final oven-temperature zone for panned bread is maintained constant at 221- 240°C, which is intended to firm up the cell-walls of the crumb-porosity, and adjust the desired crust-colour intensity. The duration of this stage is approximately the same as that of the initial stage, about 7 minutes (25% of total baking-time). This results in a loss of organic volatiles, which contributes to the 'bake-out loss'. The latter amounts to 10-12%, showing differences of up to 2'0%, owing to temperature/time variations, product weight/volume, formulation, ratio of crumb :crust, oven-design, crust-texture, and efficiency of heat-transfer. Prouty, W. W. (1965) Bakers Digest, 39, 4, p. 69. Effect of temperature variations at constant baking-time on bake-out and moisture-losses in the finished bread. Unsliced panned white bread, crumb-moisture is considered ideal for ultimate consumption when the cooled moisture content is 37-38%, but the sliced/wrapped version should be nearer 36%, although a permitted mould-inhibitor is normally added. Output-capacity of an industrial bakery depends on the baking-surface of its ovens. Visual perception by the baker, during baking, identifies: oven-proof, crumb-formation and crust-formation. Oven-proof or 'oven-spring', is the result of a high degree of gas• development and efficient gas-entrapment within the gas-cells. This should give a volume increase of 15% to 25%, and in the case of hearth-bread a height increase at the expense of its width. Crumb-porosity determines potential digestibility, forming 70-80% of the loaf. Its moisture at setting lies within the range 47-49%, which reduces on bake-out to about 37- 38%, depending on the mode of baking. Underproofed dough-pieces, on setting, require a reduction of the oven feed-end temperature, and an increase in humidity input. The latter, within a closed chamber, increases the pressure, thus countering the pressure developed by gas-production within the dough-piece. This hinders excessive initial rising, and dough-surface condensation retains it longer in the elastic state until gas-development and expansion is complete. Noles and references 767

Overproofed dough-pieces on setting, require an increase in feed-end temperature, and the humidity input decreased accordingly, both of which exert the opposite effects on the dough• piece. Thus loaf symmetry can be retained, and the formation oflarge vacuoles in the crumb avoided. Hearth-breads require the input of 70-80% relative humidity during the initial baking stage, which represents about 20% of the total baking-time. However, since the accurate measurement of humidity within the baking-chamber presents technical problems, the baker must rely on experience with his particular oven-system. Also, no exact guidelines for steaming-levels to apply to individual products are possible. Optimal steam-input levels will depend on the consistency of the dough-piece, and its degree of proof. In the case of hearth-breads, after the initial humid stage, most of the steam is released by opening the oven-chamber vents. Oven humidity is regulated by either injecting steam into the chamber, e.g. for products with a high percentage of crust such as bread-rolls, or release through the chamber-vents. An approximate guideline is 100 kg of hearth-bread require about 3000 kg of steam. With modern ovens, this is supplied from outside the oven-chamber as saturated-steam under pressure at about 30 kPa. Where older ovens are in use, 'steamers' (steel-boxes containing water) can be placed within the chamber, or dough-pieces can be either painted or sprayed with water before setting. The latter technique supplements dough• piece surface humidity in all situations. Steam-injection is widely used in Europe for hearth and crusty products, injection taking place in the first or second heat-zones of the chamber by lateral steam-headers. These provide saturated, low-pressure steam over the top of the dough-pieces during the first 2-3 minutes of baking, at a velocity of about 300 ft/min. Since steam volume varies with pressure, steam is more accurately measured by weight, i.e. the amount of water which the boiler must evaporate to produce it. Boiler capacity often being quoted as 'boiler hp/lb of dough', e.g. 1·0 to 1·5 boiler hp/100 Ib of dough is regarded as optimal. Oven-capacities of 1000lb dough/hour would require 10- to 15-hp boiler. The prime purpose of steam injection is to effect condensation on the cool dough-surface, enabling it to remain elastic long enough to expand to a maximum without a ragged break and shred. Other functions of primary live• steam before setting or firming of the loaf are improvement of , bloom', and evaporation loss control. Secondary-steam is that produced during baking by evaporation from the dough• piece. The use of steam for panned-bread production is now less common, since the secondary-steam generated is considered adequate. With travelling-band tunnel-ovens, steam-injection is only used at the feed-end and zone 2, since, when used at a later stage, it can produce a tough, leathery crust. This is due to gluten boiling on the dough-surface instead of being coagulated in a less humid atmosphere. Prolonged retention of steam, after about 15 minutes baking-time results in tough crusts. Bake-off in a relatively dry atmosphere imparts crispness to the crust. Steam removal is controlled by dampers, positioned along the oven length. All steam-lines from boiler to oven must be insulated to retain steam-quality, and save energy; this prevents condensation, and any carryover of moisture droplets into the oven, causing surface blisters on the products. Low-pressure steam is ideal for baking, its temperature approximating to dough-temperature rather than oven-temperature. At 100 to 115 u C steam is in a water-saturated state, and condenses on the cool dough-piece. Steam at 10-15 psi pressure from the boiler, reduces to about 5 psi through the injector. If the steam were at a higher pressure, and temperature, insufficient time would be available for it to fall to the point of condensation (dew-point) before the oven temperature had raised it again to dough-surface temperature. Also, high pressure/temperature steam would exert a depressing effect on loaf-volume, especially rye-doughs. Heat-transfer from source to dough-piece must be accomplished within an optimum time• period to complete crust and crumb formation, browning processes, evaporation of moisture, and elimination of all microorganisms. If too rapid, the outer dough-layer becomes burnt, and the internal layers remain incompletely baked-out, the heat-transfer from outside to 768 Handbook of breadmaking technology

inside not having been correctly synchronized. When heat-transfer proceeds too slowly, the crust formation is inferior, and the internal-layers become dried out. Optimum baking-time and throughput-capacity of the baking system utilized is essential for consistent bread-quality, and the economic operation of the oven. In the case of discontinuous or batch oven loading, bread quality is usually controlled by the baking-time and checking weight-loss. For continuous industrial baking, using travelling-band tunnel• ovens, baking-time is regulated by setting the speed of the travelling-band. This is measured with dynamometers, the electrical output being measured either by a voltmeter or a potentiometer. The relationship between band-speed and energy-output is then calibrated in terms of baking-time. The resulting instrument, giving a direct read-out in minutes of the baking-time is referred to as a tachometer. Tachometers are either direct- or alternating-current instruments, whose rotating-element is directly connected to the oven conveyor-band drive-shaft. These instruments provide a daily read-out record of baking-time when connected to a recorder-chart. Solid-state technology now miniaturizes these instruments, allowing them to be mounted integrally in central control-panels of reduced dimensions. Wheat- and rye-jiour breads differ in baking requirements and conditions, i.e. baking• temperature gradient, humidity, heat-transfer, and baking-time. Reasons for such differences are: composition and properties of wheat and rye doughs; lower density of wheat v. rye doughs: leavening procedures, wheat (yeast) v. rye (bacterial). Wheat-bread and bread-roll products differ in baking requirements and conditions owing to the extreme difference in size and weight and also to the relative ratios of crust :crumb. Weight ofsteam required increases with decreasing product weight, owing to smaller products having a larger surface-area, and crust percentage than the larger units. An approximate guide is 130 to 150 g/m 2 of dough surface. 1 kg hearth-baked wheat-bread, baked at 240°C, falling to 220°C over 40 minutes, would require about 2000 litres of steam/l 00 kg product. Whereas, 45 g wheat-rolls, baked at 220°C over 18 minutes, would require 3000 litres of steam/IOO kg product. Bread-baking requires oven temperature programming such that the temperature-gradient is a falling one. This procedure is both technically and economically justified, but can only be successful where ovens are under automatic temperature control. Baking-loss and the thickness of crust must be under strict control to produce products of acceptable baked quality. In many Eastern European countries this is regulated, and laid down as a standard, together with the baking-time. For example, in the GDR, a basic bread variety such as a 1·5- kg hearth-baked mixed rye/wheat loaf, must show a baking-loss of 11-12%, which demands a baking-time of 50-60 minutes at 280°C falling to 210°C. Heat-energy, required to bake a I-kg loaf of bread is approximately 500-600 kJ, depending on oven type, type of heating, and degree of automatic control of the heat-transfer system. Heat-jiux and heat-transfer during baking can take three different modes, i.e. convection (movement through gaseous media); conduction (movement through solid material); and radiation (emission from surfaces). Which mode predominates will depend on oven-type and design and energy-source. Convective heat-transfer, involves the atmosphere within the baking-chamber, a variable mixture of air, steam and fermentation volatiles, and its circulation speed. The convection heat-transfer coefficient is expressed in kJ m - 2 h - 1 K - I. Under static atmospheric chamber conditions, this is of the order of21 kJ m - 2 h - 1 K -I; but at a velocity of lOms- 1 this increases to 168kJ m- 2 h- I K- 1• Korb, W. (1958) Oven Construction and Heat Engineering (German), p.6. Technical Department for Large Oven Construction, Werner and Pfleiderer, Stuttgart, FRG. Conductive heat-transfer depends on the type of material used for the oven-sole, i.e. steel- Notes and references 769

plate, steel-mesh or fire-brick. It is the result of molecular oscillation within the the material, and is expressed in terms of the coefficient of conductivity (kJ m - 1 h - 1 K - 1). Radiation results when there is a temperature-gradient between a body and its surroundings. The heating-elements of the oven chamber emitting heat in the radiant mode. However, this type of non-ionized radiation can only penetrate a few millimetres into the dough-piece, after which heat-transfer proceeds by conduction. The radiation coefficient is expressed as kJ m - 2 h -1 K -4, depending on the temperature of the radiating-element. A temperature increase by a factor of 2, requires a radiant heat-energy increase by a factor of 16. Wheat, rye and mixed wheat/rye doughs, although similar in baking behaviour, show certain specific differences in reactants and reactions taking place in the oven. Visual differences are apparent as differences in crust-colour, and bread-crumb character. Rye-bread crust-colour is predominantly chestnut, whereas that of wheat-bread is golden-yellow to dark-brown. The influence of these differences become apparent when blends of rye- and wheat-flour from 100% to 0% are made at 10% increments. Rye doughs have more free amino acids and types of sugar than wheat doughs. These compounds become involved in the melanoidin-forming Meyer reaction, which considerably enhances rye bread flavour. Significant decreases in free lysine, leucine, valine, xylose, arabinose, galactose and glucose occur during rye-bread baking as a result of such reactions. Minimum baking-times for hearth-breads of the same scaling weight, containing various percentage mixtures of rye- and wheat-flours, show decreases with increasing percentage of wheat-flour in the mixture. The higher gluten content of wheat• bread dough results in a higher thermal conductivity, on account of superior leavening properties. The time necessary to reach evaporation temperature at the centre of the loaf• crumb is less than in the case of rye-bread dough. Bread-roll products may reach evaporation temperature within about 6 minutes of setting in the oven, but the dough-pieces must remain at 220°C for 18 minutes to ensure an acceptable baked-quality of the crust and crumb. Baking-times and temperatures for specific products must be adhered to for baked-out quality. To control starch gelatinization, and protein denaturation, the centre of the dough• piece must be maintained at 98°C for at least 10minutes to avoid a damp, inelastic crumb and premature staling. The ratio of crumb:crust varies with the type of product. Schwate, w., and Ulrich, U. (1983) Special Processes in Baking, 2nd edn, (German), published by VEB-Fachbuchverlag, Leipzig, GDR (see Fig. 109, p. 179-Average crumb-crust %ages of bread and rolls). Sales success o/, bread as a basic food commodity depends on strict control of the baking process. Baking-time has a profound effect on aroma and flavour build-up of all baked products. These, and product freshness, constitute the sensory appreciation of the consumer. Substances amongst those forming the aroma profile of bread are: acids, alcohols, esters and lactones, carbonyls, pyrazine, sulphur-compounds and phenols. These produce the final taste sensations of acidity, sweetness, saltiness and bitterness, all of which must be optimally balanced. These, together with the thermally modified lipids, proteins and carbohydrates, combined with ethanol, water, fermentation by-products and gas-development make up the product consistency. The latter contributing to the taste sensation on the tongue and general mouth-feel. Rustic products with a 3-4-mm crust thickness are increasing in popularity. Such breads have a strong aroma, and well-developed aromatic and 'nutty' flavour. Most of these are based on rye or mixed wheat rye milled products, but the addition of oat milled products, e.g. oat• bran and oat-germ, and malted cereals, will add value both nutritionally and from a flavour viewpoint. By comparison, standard wheat and wheat/rye bread varieties and bread-rolls require a larger percentage of crust, and to be freshly baked and crisp. Bread-rolls having a limited shelf-life of 6 hours, and 2-3 days in the case of breads. The choice o/' bread variety or bread-roll type will depend on the food or drink with which it is consumed, thus producing an ideal harmonization of the various taste and flavour 770 Handbook of breadmaking technology

components. However, bread flavour is critically influenced by the baking-process, and crust• thickness. In countries where more wine than beer is consumed, e.g. France, white-bread predominates in the form ofthe baguette, which has 32-36% crust. Whereas, the average loaf of white-bread has only about 20-25% crust. Crusty white-bread is the ideal accompaniment to complement the pleasant fruity/acid flavour notes of good wine. Bread neutralizes the wine• acids, allowing increased consumption without any adverse effects due to excess stomach• acid build-up. The bake-out loss ofa baguette is about 20%, which is twice that of an average white panned-loaf. In Germany, the 'Salzstange' is very popular with both beer and wine, and is found all over Germany in the restaurants. The dough is given a short proof before being rolled out in an elliptical form and rolled-up. After being painted with water, they are covered with salt and caraway-seed before setting in the oven. Most of such rolls are prepared from a lean 'water-dough', with no shortening or sugar enrichment. Another type is the 'Mohnsemmef, made in the form of a rosette, wreath or straight, from a lean dough. Before setting, the dough-piece is moistened and strewn with blue poppy-seed. Bread-flavour development does not depend on the use of an oven-fired with solid fuel, and the entry of the flame into the oven-chamber. Excellent quality and flavour breads can be baked in multi-deck and travelling-band tunnel-ovens. Temperature and temperature/time control within the dough-piece during the baking cycle are more important than oven-type, construction or energy-source. Heat-transfer from oven to dough-piece must reach a 'steady• state' condition, the heat-flux being sufficient to penetrate the dough mass and evaporate the water, leaving the crumb structure intact and elastic. Any excessive heat build-up at the crust• surface must be avoided, since this results in wasteful 'burning' of the top-crust instead of a controlled bake-out and browning. A I-kg hearth-baked white loaf requires an average of 40 minutes to bake out, when set at 240°C, falling to 220°e. Whereas, a I-kg rye or mixed wheat/rye variety would require a higher initial temperature of 250°C, falling to 210°C over 50 to 60 minutes, to give optimum flavour development. Doughs made from rye-meals, and panned rye doughs require similar temperatures, but with reduced top-heat, and stronger bottom-heat, baking-times being up to 120 minutes for a 1·5 kg scaling weight. Baking-loss is a function of baking-time, scaling-weight, and loaf-surface exposure. Loaves of 1 kg or more give baking-losses of 10-13%, whereas bread-rolls lose from 18-20% during baking. In general, the larger the unit the smaller the net baking loss. Pre-baking (Vorbacken), is a technique often applied to rye-bread baking to improve flavour, crumb-elasticity, porosity and shelf-life. The larger 1'5-kg units are exposed to temperatures of 420°C for about 2-3 minutes, which gives the loaf an extra 1 mm of crust, using the normal baking-time and temperature subsequently. This increases the crumb-moisture retention, and bread-yield increases from 135 to 138 kg bread/100 kg flour for mixed rye/wheat breads. Crumb-centre temperature must reach 98°C, and when this has been reached the optimal baking-time has almost lapsed, but the crust-surface can reach about 160°e. Differences in specific heat between wheat and rye doughs, mean that the same dough-piece weight of wheat dough will reach the critical 98°C at the centre on average 10-12 minutes before that of a rye dough or mixed rye/wheat dough-piece. Specific heat differences between wheat and rye doughs are due to differences in moisture content, i.e. 45-46% v. 53-55%, their material structural porosity, which in turn favours thermal conductivity through the layers in the case of a wheat dough. Specific heat is defined as the quantity of heat required to raise the temperature of unit mass of material from t to (t + 1) DC, at any temperature t. The unit of specific heat capacity is J kg - 1 K - 1 SI units, or cal g K - 1 in the CGS system. Temperature differences of 1°C = 1 K (kelvin). Approximate specific heat capacities ofleavened dough range from 2·80 to 3·0 kJ kg-I K -I, depending on dough water-content, ranging from 45% to 55%. Theoretical heat requirement to bake a I-kg loaf has been calculated to be 500 to 600 kJ, but such values take no account of such technical heat-losses as: exhaust-gases, unburnt-gas, heating-up, radiation, steam-evaporation, incorrect secondary-air feed at the burner. Notes and references 771 CHAPTER 3.2 ELEMENTS OF THE BAKING PROCESS AND THEIR CONTROL

Baking process is the most energy-intensive operation of bread production, and 30--40% of all bread-faults are due to baking inadequacies. Therefore, optimization of the controllable variables is very desirable. The fate of the shaped and proofed dough-piece during the baking-process under the influence of the following variables must be carefully analysed: heat-energy input and temperature; heat-transfer; humidity; and baking-time. The unit of heat in the SI system is the joule, which can also be expressed in non-SI system CGS units as calories. 1 calorie = 4'1868joules (J). The quantity of heat-energy dQ, absorbed by a body of mass m, when its temperature is increased by dt is: dQ = sm dt, s being the specific heat of the body. The sum of the quantity of heat a body absorbs on heating, and the work d W performed in so doing, represents the change in internal energy, dl, i.e. dQ + d W = dl, the First Law of Thermodynamics. Any change in internal energy, dl, will depend on the final and initial state of the dough-piece, and is independent of the actual heating process, whereas both dQ and d W depend on the transition process. The fact that heat cannot be spontaneously transferred from a colder body to a hotter one without a change in the system is known as the Second Law of Thermodynamics. The Third Law of Thermodynamics states that the specific heat of a body approaches zero as its temperature approaches absolute zero on the thermodynamic temperature scale. The point of 'absolute-zero' on the thermodynamic (Kelvin) scale being 273·15 K below the melting-point of ice at standard pressure. This being the baseline for temperature measurement on the Kelvin scale. Temperature is a measure of the average chaotic motion or kinetic energy of the molecules within a substance, and their velocity of oscillation or movement. This energy of movement can be increased by the application of an adequate amount of heat-energy, which raises the temperature of the body, unless it loses heat simultaneously. Temperature, as an expression of heat-intensity, can be reduced or increased by the control of the heat-energy input. After setting a batch of bread in the oven, the temperature falls, unless more heat is applied. Therefore, in transforming the dough-piece into a loaf of bread, a specific quantity of heat-input is expended. This quantity varies with oven-design, heat-loss management, dough-piece weight and dimensions, efficiency of the heat-transfer systems, loaf-spacing within the chamber, humidity-control, and the use or non-use of pam.. The average range for a I-kg loaf being 500-600 kJ, most of this heat-energy is transferred to the dough-piece in the radiated form, which means that the oven-chamber walls must attain temperatures between 300 and 400°C to bake the bread. Heat transferred onto the dough-piece by radiation, conduction and convection currents, and steam condensation, must be further transferred by conduction from the peripheral layers into the centre of the crumb, as shown in Figs 87, 88 and 89. The graphs shown in Figs 90 and 91, show the ideal temperature/time curve for hearth-bread, and the reduction of dough-piece moisture as the dough-piece rises in temperature. Oven operation and control should take into account the following: utilization of oven capacity to the full; synchronization of final-proof with oven-temperature; regular calibration of thermometers; industrial bakery ovens require regular checks for humidity, gas/air ratios and exhaust-gas analysis, chart-recorders should be monitored and interpreted; vents and loading and discharge points should be kept closed after use; draught sources near the oven must be eliminated; regular oven-maintenance is essential. Energy-utili:cation calculations are more meaningful than theoretical heat requirement calculations, owing to the numerous sources of heat-loss inherent in all ovens, e.g. exhaust• gases, steam, radiation, and firing-losses. Travelling-band tunnel ovens show the following average energy-utilization percentages: total energy-input base 100%, of which, some 45% is utilized in actually baking the bread, 35% lost as exhaust-gases, 12% lost as steam, and a residual 8% lost by radiation. Energy-ulili:calion index is expressed as the ratio of the total theoretical heat-energy 772 Handbook of breadmaking technology

requirement to bake a loaf of defined weight, to the total energy input. When multiplied by a factor 100, it is expressed in percentage terms. Alongside such data as: oven-capacity, baking• surface area, and loading characteristics, the energy utilization index is a critical parameter for bakery ovens. In effect, it is a measure of the summation: oven type and design, the energy source, and the efficiency of the operator. Improved oven-design and control techniques have reduced manual work, and improved bake• out control, but the demand for technical know-how from the operator has increased accordingly. Oven-operation requires dedicated observation, and a quick-reaction to correct any unfavourable developments. Exact temperature readings taken before loading and during the baking-cycle for checking against target values are typical routines. This enables readjustments to be made manually. If the oven temperature-control system utilizes a servo or feedback capability, providing modulated heat control, this can be computer interfaced. Oven-humidity is often judged by experience using manual control of the lateral steam• headers or jets, but this results in about 20-33% loss of steam for bread or rolls. An automatic steam-control system can reduce energy consumption by up to 10%, being linked to the hygrostat. This facility is also available on many increasingly high-technology equipped multi-deck ovens, together with check control instrumentation for the precise diagnosis of electrical and burner faults. Exhaust-gas monitors keep excess air and soot-formation limits to a minimum. Burner monitors allow comprehensive checks to be made on oil-consumption, in-built computers on the instrument-panel inform on burner operation-time, the number of switch-ons, oil-consumption, oil consumed since the last reset, as well as oil supply and tank• level, thus ensuring heating-times and baking characteristics are stabilized. Baking dough-piece characteristics demanding close observation are: crust-colour, loaf cross• sectional symmetry, volume and any signs of splitting at the sides (hearth-bread), or break and shred (panned bread). Any abnormal developments being countered by adjustments to temperature, humidity or baking-time. Energy-utilization indices are the highest in the case of travelling-band tunnel-ovens, whether fired by natural gas or electricity, and electricity provides the most efficient energy-utilization index compared with other conventional energy sources. However, national economic issues, such as natural resources available to produce energy, will override such bakery internal evaluations. Schwate, w., and Ulrich, U., Special Processes in Baking, 2nd edn, 1986, p.74 (German). Multi-deck ovens offer great flexibility when fan-assisted, cyclotherm hot-air or gas circulation is utilized. Each deck is under individual temperature control, allowing the simultaneous baking of a product assortment, or one deck to give a" 'sharp pre-bake', and another to complete the baking-process. Average heating-up rates are about 3 K/min, with the heating options oil, gas, electricity or coal. Fast and efficient loading with roll-up oven• setters is now widely applied. Relative energy-input requirements of a 4-5-deck oven for heating-up and continuous operation respectively are: gas 32·0 m3/h and 13 m3/h at 75 minutes heating-up time; diesel oil l1'Okg/h and 5'7kg/h at 75 minutes heating-up time; coal 45'Okg/h and 15'Okgfh at 120 minutes heating-up time. This data is approximate, and reflects relative energy-input differences in requirements. The average baking-surface of a four-deck oven being a total of 10m2, but can be 19'2m2 with a large deck width of3100mm, and a capacity of 240 x I-kg hearth-loaves. Ovens fitted with fire-brick tiles on the sole, known as 'chamotte', are capable of storing so much heat that there is no need to heat up again for baking, the heat being emitted more slowly than the rapid heat-transmission from steel-plates. Vogel, W. (1972) Higher productivity through utilization of the cyclotherm deck-oven (German), Backer und Konditor, 20, 26, issue 5, p. 134. Heat-energy input and temperature control and measurement is the most important routine Notes and references 773

operation in oven management. Close attention, and logging of measured data will reduce running cost to a minimum. Where natural gas is in use, the volume of gas-flow per unit time is measured with a cylinder type digital-counter, designed for various throughputs. The gas: air ratio must also be routinely checked, a minimum of air being essential for an efficient combustion. This parameter is determined by gas analysis, the quantity of air being either determined from the working pressure of the measurement-diaphragm, or the air velocity at the intake point, based on cross-sectional area. The ratio of the actual quantity of air to the minimal quantity required is known as the 'air-number', or sometimes the 'burner-number'. For travelling-band tunnel-ovens of the BN-series, manufactured in the GDR by VEB• KyfThauserhiitte, Artern, the 'air-number', or 'burner-number' should be 1·1 to 1'3, in order to avoid energy-losses, according to: Schnee weiss, R., and Klose, O. (1981) in Technology of Industrial-Baking, VEB-Fachbuch• verlag, Leipzig, GDR. Parallel checks to determine the 'air-number', are carried out by an exhaust-gas analysis, gas• analysers being available in both a stationary and transportable form. Any fall in pressure in the combustion-chamber of tunnel-ovens can be measured with a U-tube manometer or Bourdon-gauge scale read-out. This should be regulated to fall within the range 40 down to 20 Pa by exhaust-gas adjustment. Electro-energy is measured with a meter reading energy consumed in kWh or kilowatt-hours (1000 watts acting for 1 hour). Temperatures in both multi-deck and travelling-band tunnel-ovens are measured by pyrometers. These instruments operate on the expansion principle, consisting of a bimetallic strip, often iron and copper of differing coefficients of expansion. The resulting deformation of the bimetallic-strip at different temperatures is then measured by registration on a calibrated scale of the movement of a cogged-strip, which keys into a cogged-wheel attached to a rigid pointer. Such instruments depend on conduction, whereas true pyrometers measure radiated-heat (infrared), either by changes in electrical resistance, or millivolt differences of the order of 5-6 m V per 100 K. Thermocouples for resistance-thermometers consist of nickel and platinum, and those depending on thermal-voltage differences, measured in millivolts, consist of iron-constantan couples connected to the pyrometer by copper wires. Continuously working ovens require temperature measurements not only within the various zones of the baking-chamber, but also within the burner-space and circulation-system. This involves temperature gradients of 150 to 600°C, which are measured remotely with either thermo• elements or electrical resistance thermometers. An electrical output-signal controls the gas• feed and the burner temperature. Uniform temperature-control requires the application of either continuous, or at least a three-point control system. A new type of temperature sensor, which can float on an air-cushion, like a mini-hovercraft, just 2 mm from the dough-piece, depends on convection instead of radiation or conduction. This floating sensor rides on convection currents drawn over the surface of the dough-piece, a thermocouple measuring the air temperature. Requirements for measurement of localized convective, radiative, or total heat-transfer rates have resulted in the development of several types of heat-flux sensors. The slug-type sensor consists of a slug of metal embedded in, but insulated from, the surface across which the heat-transfer rate is to be measured, a thermocouple being connected at the rear interface between the slug and surrounding insulation. The Gardon Gauge represents a 'steady-state', or asymptotic type of sensor. Gardon, R. (1953) Rev. Sci. Instrum., May issue, p.366. An instrument for the direct measurement of intense thermal radiation. It consists of a thin constantan disk connected at its edges to a large copper heat sink, while a very thin, 0·005 in diameter, copper wire is connected at the centre of the disk, thus forming a differential thermocouple between the disk centre and its edges. When the disk is exposed to a constant heat-flux, an equilibrium temperature gradient is established, which is proportional to the heat-flux. The thermocouple signal, being directly proportional to the heat-flux, no corrections, or thermocouple reference junction is necessary. With the Gardon gauge, there is 774 Handbook of breadmaking technology a radial temperature gradient over the disk, which if excessive, causes a variation in the local convection-coefficient and thus an error. However, when only the radiation component of the total flux is required, the front of the sensor can be covered with a thermally isolated sapphire window, which passes the radiation-flux, but blocks the convective-flux. Heat-transfer from energy source to dough-piece occurs in three forms, depending on oven design, viz. conduction, convection and radiation. Conductive transfer takes place from the oven-bottom of 'sole', depending on its area of contact with the surface, and the material of the oven-sole, i.e. steel-sheeting or refractory (chamotte) tiles. It results from molecular oscillation within the material as a result of an intense heat-energy input, being expressed as the coefficient of thermal conductivity, the units in the SI system are kJ or J m - 1 S - 1 K - 1, W m - 1 K - 1, and kcal m -1 h -1 K -1 in cas units. This constant for any given material, is expressed as the rate of flow of heat through a surface of defined area, where the temperature• gradient normal to the surface within a fixed time is measured. Its value will depend on both moisture content and temperature. In the case of gases within the baking-chamber, the thermal-conductivity, expressed in W m - 1 K - 1, will depend on both pressure and temperature. The oven atmosphere also transfers heat by convection, which involves atmospheric movement in the form of convection currents. This involves the movement of steam and volatiles either as the result of opened vents or by fan-assistance. Convection heat• transfer coefficients, expressed in kJ m - 2 h -1 K - 1, depend on the air-speed within the oven• chamber, increasing from about 20 kJ m - 2 K -1 when static, to 160 kJ m - 2 K -1 at air-speed 10 m s -1. The third form of heat-transfer, radiation, can only penetrate a few millimetres into the dough-piece, but the heat-emitting elements of the oven effect a heat-exchange with the chamber atmosphere, and the resultant heat-flux initiates the conduction mode of transfer. However, the total heat energy transfer to the dough-piece by convection, remains quite insignificant unless some form of forced heat circulation is introduced within the chamber. During the initial period of the baking cycle, a very significant mode of heat-transfer to the dough-piece is the heat of condensation of the steam onto the dough-surface and adjacent surface-layers. The latent heat of formation is released as heat-energy. The optimum adjustment of baking-chamber humidity by steaming emphasizes the importance of steam as a heat-transfer medium in baking. Warming up of the dough-layers in the crust-forming zone changes the temperature/baking-time curve in the crumb-centre zone, therefore, care should be taken to fix the optimal level of humidity for products. Forced-convection heat-transfer techniques are designed to provide maximum heat-transfer by adjustment of air-speed and volume of air in circulation. Often air is circulated through slots into the chamber being forced from a chamber located at the base of the oven. Alternatively, the oven atmosphere is recycled by a fan system, removing hot air from the top of the chamber, and inserting it through perforated tubes located above and below the baking-product. Direct-jiring is the most economic and the simplest method of heating ovens, giving up to 25% more efficiency compared with indirect methods. Natural gas is the most popular source of energy in many countries, owing to availability and cost. The introduction of the ribbon-burner systems, with a flame-band distributor having found general acceptance. The resultant gas:air mixture remains constant and efficient, and provides good heat distribution, even with natural convection turbulence. Heat-penetration and migration of moisture from the loaf-centre demand considerable latent energy. Therefore, moisture emerging from the dough-piece as steam should be removed by air-turbulence as soon as possible, thus promoting heat-penetration. All evaporation must be completed before crust-formation takes place, since this prevents it. Also, any prolongation of this stage will result in a thick, tough crust. Panned-bread baking demands efficient convective heat-transfer systems ensuring a fast and uniform bake. This is best achieved by a complex system of turbulence, provided by Noles and references 775

impingement-modules, equipped with tapered-jet nozzles directed both downwards and upwards, carrying hot air onto the dough-piece surface, in close proximity to the oven band• conveyor. With such a system of air-impingement, air-velocity rates of 3000 ft/min are possible near the nozzle-orifices. Impingement air ovens permit the use of lower baking-temperatures, and shorter baking• times. Thus yielding products of higher moisture contents, and prolonged staling-rates, with lower net energy inputs. This technique is appropriate for white panned bread, especially in the sliced and bagged form. Smith, D. P. (1985) AlB Paper: Update on Oven Technology Seminar, Orlando, Florida, September 21, 1985, Jet accelerated convection baking. Smith, D. P. (1986) Food Technology, 40, p.112. Improved air circulation in indirectly fired band-ovens can be achieved by the recirculation of air within the chamber at 200 to 400 ft/minute. Hearth-bread baking requires another technique involving a slower bake. Heavier, lower specific-volume white and variety-breads such as rye and pumpernickel demand this procedure. The solid-steel, refractory (chamotte) tile, or wire-mesh bottom-heat reduces radiation, and cuts off the free flow of convected heat around the dough-piece. Therefore, heat-transfer by conduction becomes predominant, involving a slower bake. The chamotte stores heat, and releases it slowly and progressively. Baking-times approximate to 60 minutes for a I-kg loaf v. 27-30 minutes in the case of an equivalent panned white-loaf. Accelerated heat-transfer under the trade name 'Acceletron', introduced by I. Rhodes, in 1965, depends on the development of a 'corona-wind' within the oven-chamber. An electrode-grid sets up an electrostatic field of high potential and constant polarity between the oven-crown and the hearth. The device is installed parallel to the steam-headers, ionizing the gases near the electrodes, the ionized gas molecules then becoming repelled by the electrodes, giving rise to a downward current of air towards the product. Reduction in baking-times of up to 20% have been achieved with this equipment when installed within the front 25% of baking• surface, using a high-voltage direct current discharge during the first 4-5 minutes of baking. Ozone is simultaneously liberated in trace amounts, as is normal with electrostatic discharges. Sievers, R. S. (1978) Proc. Am. Soc. Baking Engineers, p.98, obtained the best results by reducing the temperature within the first two heat-zones by 28 to 45°C with adequate steam input, and reducing the final heat-zone by 14°C. Commercial trials indicated the most important advantages of accelerated heat-transfer to be: (1) reduced spacing of the pan• straps, allowing a 10% increase in oven-capacity; (2) an average energy saving of 11·8%; (3) a reduction in bake-out loss, allowing a scaling-weight reduction of 0·5-ounce (14 g) for a 24- ounce unit. Reduced bake-out loss, giving average savings of 0·5 to 1·0 ounces (14-28 g)/lb (454 g) of dough. Electrohydrodynamic heat-transfer in some oven applications, are aimed at improved steam application, enhance transfer by radiation versus convection, thus allowing even closer pan• strap spacing on the oven grid. Modulation heat and temperature-control units for any oven-zone ensure that the correct air: gas mixture is linked to a temperature-control unit, sensing the temperature in the zone of burner operation, feeding back a signal when more or less heat is required. Fig. 95 shows the link-up controller, actuating an electric modulating motor on the combustion air-line. Such devices allow oven-zone temperature to be maintained within a few degrees of instrument preset, the controller being accurate to within 1·0% of the scale range. Conventional heat-transfer techniques must ensure that the centre-temperature of the loaf reaches 96 to 98°C, in order to attain the fully baked state. 776 Handbook of breadmaking technology

Oven-atmosphere ionization can bake a 22-ounce (616 g) square Pullman-Ioaf(pan with cover) within 17 minutes, the loaf-centre temperature remaining below 43°C up to the 7th minute, then rising rapidly over the next 7 minutes, levelling out at 88-93°C during the last 2·5 minutes in the oven. Accurate temperature control can be obtained with the electronic potentiometer, which gives readings accurate to ± 0·25% of total scale-range. Pyrometers based on the millivoltmeter being slower and less sensitive in response. Thermometers based on the pressure principle, whether of the coiled Bourdon- or capillary-tube design, have scale range accuracies of about ± I % maximum. Thermoelectric temperature and control systems find the widest application, since any number of thermocouples can be connected to one instrument. However, it is advisable to have one instrument serving each individual heat-zone of an oven, complementing each indicating controller with its own recording-chart to monitor temperature changes within each zone during the baking-cycle. Electronic-pyrometers can be adapted to give modulating heat control, keeping oven temperature within narrow limits. Optimal humidity concentration within the oven-chamber is important for end-product quality of hearth- or variety-breads, bread-rolls, and specific types of cake. At every temperature, air is capable of holding a specific maximum of steam (kg water/kg of dry air), and when this amount is exceeded, condensation results. At 20°C, under atmospheric pressure, the ra~io of steam:air (kg) is 0'015, at 90°C 1'56, but at 99°C it reaches 200. At temperatures in excess of 100°C, the water-holding capacity of air is such that steam can be mixed with it in increasing amounts as the temperature is increased. The point of saturation of steam in air is referred to as the 'dew-point', every amount of steam in air, depending on the prevailing pressure, has a dew-point temperature. During baking, this dew-point temperature falls between 70 and 90°C, which corresponds to a steam content of 0·29 to 1'56 kg per kg dry• air. As long as the dough-piece surface temperature during the initial stage of baking remains below the appropriate dew-point temperature, moisture will condense onto its surface, releasing 2270 kJ/kg of steam. Most of this free heat-energy is either absorbed by the dough• piece owing to conduction, or is deposited onto it as the water condenses. However, the effect of this condensation-heat is limited to the initial stage of baking only, since after about I to 3 minutes baking-time the dough-surface temperature will exceed the dew-point temperature. The ideal type of steam is at low pressure, produced with a boiler-gauge pressure of about 10-15 psi (68'94 x 1Q3Pa to 103-41 x 103Pa), reducing to 5psi (34-47 x 1Q3Pa) through the injection-nozzle. Steam at 10 psi pressure, in the saturated state, has a temperature of 115°C, whereas at atmospheric pressure (760mm mercury) only 100°e. With the reduction in pressure, the steam temperature falls with its water-holding capacity, resulting in condensation onto the relatively cold dough-piece at 30-35°e. The porous structure of the dough-piece allows both sorption and condensation on the surface and within the dough• layers. Condensation retains the dough surface in a moist, hydrated state, allowing expansion without cracking or splitting up until the surface temperature reaches I 00°e. The presence of humidity accelerating heat-transfer to the crust, surface-layers and central zones of the loaf at the same time. The curves of Fig. 98 illustrate the effect of the temperature/baking-time response of the various loaf-zones both with and without humidity, up until the completion of baking. Dough-moisture increases at doughmaking also contribute to the speed of heat• transfer, especially the surface-layers. Rye-bread baked on the hearth requires the injection of steam at the right time, and in the correct quantity for bread quality. Often, depending on oven design, the optimal adjustment of humidity and top and bottom heat during this stage of humidification becomes critical, falling into a narrow range. If the initial-zone temperature is too low, and the humidity also too low, the crust will develop both side and top splitting. The required levels of temperature and humidity depend generally on the recipe, mixing, proofing-conditions, size and shape, as well as spacing of the dough-pieces within the oven. Where no steam-injection facility is available, one has to rely on spraying, or moistening the dough-pieces with the help of a large Noles and references 777

brush before setting in the oven. Dough-pieces, which have to be baked in a state of underproof, in an emergency situation, can be given an ample supply of steam. This sets up a pressure increase within the oven-chamber, which counteracts the increasing pressure within the dough-piece itself owing to gas-development and expansion. As a result uneven oven• proof and spring ofthe dough-piece becomes suppressed, and the dough-surface is kept moist and elastic up until expansion is complete. In baking rye and mixed wheat/rye breads in a batch-type oven, the bread is set at 250 to 280°C, and the steam kept in the oven for up to I minute. This allows enough time for the steam to condense on the dough-surface, after which the steam-vent is opened, allowing colder air to enter, replacing the hot, humid air. Radiated heat then takes over, removing moisture from the crust more rapidly and effecting a general drying-out of the dough-piece. The remainder of the baking-time should then proceed at a lower temperature to prevent excess crust browning over the average 55-60- minute total residence time. In travelling-band tunnel-ovens, this can be precisely controlled, whereas in batch ovens, the bread is often transferred to a cooler oven-deck chamber. Weight-changes in the dough-piece within the oven-chamber atmosphere upon intensive initial-stage humidification were studied by Micheljew, A. A., in the USSR, and published in: Special aspects of bread baking heat-technology, Micheljew, A. A., Alma-Ata, 1943 (Russian). The plot of dough-piece weight v. baking-time in Fig. 99 shows that the maximum weight gain occurred between the third and 5th minute of baking-time; the dough-piece increasing by 1·3% over its scaling-weight. Moisture-migration or 'flux', often referred to as 'thermal-moisture-conduction', results from the movement of moisture from the outer crumb-layers progressively towards the loaf centre, owing to the large temperature gradient between the outer and inner crumb-layers, especially during the initial baking stages. This phenomenon was confirmed experimentally by A. S. Ginsburg in the USSR (see Fig. 100). Conclusions of subsequent work carried out by L. J. Auerman under constant baking temperature, and without added humidification are detailed in Section 3.2. Oven-chamber humidity or dew-point measurement at temperatures in excess of 100°C are carried out with the wet and dry-bulb psychrometric procedures, since these methods give an instantaneous response to moisture variations (see Fig. 101). This involves the measurement of the temperature diffence between a wet and dry-bulb thermometer, from which the 'dew• point' temperature, and absolute moisture content of the baking chamber atmosphere in kg steam/kg of dry-air can be deduced. This is calculated either from a chart, or by using psychrometric formulae. The chamber atmosphere is sucked out by means of an extractor• pump at a speed of 3 to 5 m/s (approximately 1000 ft/min), as shown in Fig. lOlA. The high velocity is essential to maintain the wet-bulb-surface moist; also, to avoid any condensation before the measurement, the bulb must not be allowed to fall below the dew-point temperature. During continuous measurement, the psychrometric effect must be maintained with an even stream of chamber-atmosphere. Dry-air in the exhaust-pipe should be cooled to below 150°C to ensure a flow of water in the exhaust and evaporation tube is maintained. Thermocouples are used to record the temperatures of both wet and dry-bulbs. For continuous recording and control of humidity, electrical transducers of the Dunmore type now find wide application. The lithium chloride sensor is very sensitive to humidity over 11 %, showing a sharp fall in electrical resistance. Modification gives a signal related to dew-point temperature. Fig. 103 shows how the various products respond over the total baking-time v. dew-point temperature. Fig. 102 shows the difference in humidity distribution within a travelling-band tunnel-oven, under conditions of correct external-draught exclusion (A) and where an influx of cold-air exists (8). Product baking-time, can be defined as the minimal time required to provide adequate starch gelatinization, protein coagulation, following oven-proof; and the formation of colour and flavour compounds. However, these processes must take place within a controlled time sequence in order to ensure that the internal structure of the product is well leavened, of even 778 Handbook of breadmaking technology

texture and has an elastic crumb. When the starch gelatinization temperature is traversed too rapidly, many starch granules have insufficient time to swell or gelatinize, but instead become encapsulated by other granules already gelatinized, and therefore cannot absorb enough moisture. The resultant products will show a crumbly, dense, doughy and inelastic crumb structure. In many industrial bakeries, the upper limit of the baking-time is determined by economic factors as a matter of priority, i.e. potential after-sales shelf-life with crumb• moisture levels of 35-38 %, oven-throughput rationalization and maximum energy economy. This approach often results in a reduction in quality standards of the baked product, owing to inadequate bake-out. Without appropriate consumer protection legislation, coupled with sharp competition, this situation is unlikely to change. In contrast, the baking industry in many East European countries (COMECON) specify standards for both baking-times and temperatures for all basic bread varieties, as well as crust-thickness. In spite of conflicting interests, in the GDR, under Standard TGL-3067, the baking-times and initial and final baking-temperatures are specified, according to weight, variety and form or mode of baking, i.e. panned, hearth or Angeschoben (baked adjacently batched). Permissible baking-time tolerances for each basic variety and mode of baking are also provided. Examples of baking standards included in TGL-3067 are tabulated in Section 1.7. They originate from: Schwate, W, and Ulrich, u., Special Processes in Baking (Process Manual), VEB-Fachbuchverlag, Leipzig, GDR, 1986 edition, p. 62, Table 7 (German). Such standardization is very desirable as a contribution to bread-quality, and is facilitated by oven construction standardization. Bread quality depends heavily on adherence to optimal baking-times. This embodies, not only flavour and aroma, but also crumb-elasticity, texture, and general mastication properties. Parameters which can influence the baking-time include: baking-regime, temperatures, humidity, forced-convection, atmospheric-ionization, and dough-piece spacing on the baking-surface, as well as its weight and shape. Dough-piece compositional parameters include: flour type, dough properties, and state of proof before setting. For a chosen temperature-regime and oven heat-transfer situation, there is an appropriate oven residence-time for optimal bread quality. A I-kg long-rolled hearth white loaf can be baked at 230D C, falling to 220D C for 35-50 minutes, providing the final crust• thickness reaches at least 3 mm. The author's experience has shown that for I-kg hearth white bread (baked-weight) 40 minutes at 240°C falling to 230°C, gives the required 3 mm crust• thickness, without loss of the mild wheat-bread flavour. A baking-time of 30 minutes being inadequate for full flavour development, and 45 minutes giving rise to some loss of flavour and aroma. The difference in baking-loss of 12·5% at 40 minutes, and 11·5% at 30 minutes, although representing a financial sacrifice, based on 100-kg flour price, provides a qualitative improvement of the product which more than compensates for the disadvantage. On the other hand, using the same temperature regime, a panned white loaf should be adequately baked within 27-30 minutes, when made from a lean formulation. Using an enriched North American formulation, baking at 22rC, rising to 239°C at the discharge-end, a comparable I-kg panned loaf would be adequately baked after 23 minutes, with a baking-loss of about 10,2%, leaving a crumb moisture in the final loaf of about 36-4%. By comparison, a I-kg rye or rye/wheat hearth-baked long-rolled unit, baked under a temperature-regime of 250 c C, falling to 200°C for 50 to 60minutes would give an optimal crust-thickness of 4,5-5,0 mm. The same weight-unit, baked as 'angeschobene Brot' (adjacently batched), using the same temperature-regime, would require 65-70 minutes for complete bake-through. These practical examples illustrate the importance of the adherence to the optimal baking-time. The most common bread-fault encountered is too short a baking-time, resulting in a lack of crust• thickness, flavour and aroma. The author ventures to suggest that in the interests of bread quality, and increased sales, a baking-loss of up to 12% can be tolerated by the baker.

3.2.1 Influence of the Elements on the Dough-piece and its Components The physical effects of the elements temperature, heat-transfer, humidity and time on the dough-piece, convert it into a baked-loaf in three stages: Notes and references 779

(1) Heat penetration into the interior of the dough-piece, until the temperature of the dough liquid-phase reaches boiling point. (2) Progressive evaporation of excess liquid. (3) Browning and flavour component formation, in the form of dextrins, and carbonyls from starch and sugars, and melanoidins with the help of protein degradation products. During the initial phase of baking, the temperature differential of about 30 to 100°C has to be bridged. However, at the initial stage, the moisture content of the dough-piece cannot decrease, but rather increases due to steam condensation onto its surface. Instead the moisture is forced to migrate towards the centre of the loaf owing to progressive heat penetration. However, the crust-forming layers lose their moisture. After a considerable concentration of moisture has taken place at the central zones, this internal moisture begins to migrate outwards, in the opposite direction to the heat-transfer flux. Once the boiling-point at the loaf centre has been reached, the heat-flux from the outside is utilized to evaporate excess moisture. This process is accompanied by a slowing down of any temperature rise. When the moisture level has been reduced to a specific degree, the temperature of the dough• piece will continue to rise. Since residual moisture is bound within the capillaries of the dough, this can only be removed at higher temperatures of evaporation. The rate at which the three stages: heat-transfer flux, evaporation, and loaf-browning take place, will depend on formulation-enrichment, weight and shape of the loaf, and its degree of leaven. Colloidal and chemical changes in the properties of the dough components are the most important aspects.

Wheat and rye starches, both begin to swell at 40 to 50 c e, absorbing from 25% to 50% of their volume of water forming a viscous suspension (see Fig. 104). On penetration, the amylose starch component is the first to go into suspension, followed by the amylopectin fraction. This causes swelling, and the pressure built-up within by the water, results in a splitting of the granule outer membrane. Schoch, T. J. (1965) Bakers Digest, 39, 2, p.48, postulates that during this swelling and gelatinization, part of the amylose becomes dissolved, and diffuses out of the granules into the aqueous dough medium. Here, it becomes concentrated as the interstitial water is reduced by swelling, forming a gel on cooling, which retrogrades, thus influencing bread-staling.

Sandstedt, R. M. (1961) Bakers Digest, 35, 3, p. 36, points out that a large proportion of the starch granules remain intact during baking, owing to the limited supply of water. Such granules are now considered to form the so-called 'resistant-starch', which contribute to the non-starch polysaccharide content. Degree of polymerization of the starch in grain and the resultant flour is a function of environmental conditions during growth. Differences in molecular weight distribution of polymers give rise to variations in gelatinization behaviour (melting), as well as differences in depolymerization behaviour with enzymes. The gelatinization range of wheat starch is 56 to 64°C. Degree of mechanical starch-damage sustained during milling is also important during the baking process. Although exhibiting increased water absorption, damaged starch granules are also susceptible to enzymic attack, and within the range 43 to 60°C alpha-amylase is most active. The enzyme attacking the granule between 55 and 90 c e before gelatinization is complete (see Fig. 108). SchneeH'eiss, R. (1965) also found that at temperatures between 57 and 79°C within the dough-piece, the number of damaged granules increased dramatically. This situation occurred after about 20 minutes baking-time, the isolated starch being coloured by china• blue, which only colours damaged granules (see Figs 106 and 107). Fig. 107 indicates how the 780 Handbook of breadmaking technology

water-soluble carbohydrates increase during baking from 14·5% on setting in the oven, steadily rising to 24% after 60 minutes baking-time. Fig. 108 indicates that alpha-amylase is most active within the temperature range 50-60oe, tailing-off abruptly at 70°e. Wheat and rye starches differ in their gelatinization response. At 55°e, 40% of rye starch has already gelatinized, whereas wheat starch has only just begun; at 60 oe, up to 80% rye starch has gelatinized, compared with about 20% in the case of wheat; at 6SOe, rye starch has reached about 90% gelatinization, compared with about 45% for wheat. Even at 70 to 75°e, the wheat starch gelatinization level only reaches about 80% maximum, whereas rye starch reaches over 90% at that temperature range. Fig. 105 shows in schematic form the importance of the starch granule, and the diverse reactions in which it is involved during the baking process. Alpha-amylase activity is influenced during baking by dough pH and salt concentration in addition to temperature. Both gelatinized and damaged starch are very susceptible to attack by alpha-amylase, resulting in the formation oflow-molecular-weight dextrins and only small amounts of maltose, accompanied by trace amounts of glucose and low molecular weight saccharides, e.g., amylotriose, amylotetraose, and amylopentose. Pazur, J. H., Sandstedt, R. M. (1954) Cereal Chemistry, 31, 5, p.416. At pH 4·3 to 4·5 (acidity-index 10-11) in rye doughs, and temperature 60 oe, and pH 4·7 to 4·8 (acidity-index 4-6) within temperature range 73 to noe, alpha-amylase becomes almost completely inhibited. Rye doughs at pH 4·9 (acidity-index 4'4) show alpha-amylase activity in the centre of the bread-crumb up to temperatures of 96°e. Inactivation temperatures for the amylases for both wheat and rye breads depend on the rapidity and duration of the baking process. Susceptibility offlour starch to alpha-amylase attack, depends on the particle-size distribution (granularity) of the flour, the size of the starch granules, and their degree of mechanical damage during the milling process. The greater the molecular surface exposure of the starch granule and its fragments, the greater the enzymic susceptibility.

Salt delays the beginning and reaching of the peak gelatinization of flours by 5 to 100e. Huber, H. (1964) Brot und Gebiick, February issue (German). Salt and acidification in the correct quantities gives rye-flour similar properties to that of wheat-flour, allowing optimal baking properties. Huber, H. (1964) Brot und Gebiick, February issue (German). Products with smaller cross-section, e.g. bread-rolls and baguettes, reach 99°e at the crumb• centre within about 8-10 minutes, leaving a further 20 minute exposure, resulting in almost complete starch gelatinization. Panned units of 1 to 2 kg experience limited starch-pasting only, hence, many granules, apart from slight thermal deformation, remain in the crystalline form. This is confirmed by the retention of the birefringent (German: doppelbrechenden) interference-cross, when viewed under polarized-light microscopy.

High~fi'equency (H F) baking techniques, using VHF (17'7 MHz) energy as a two-stage baking process, results in the dough-piece remaining in the gelatinization-zone for about one-third of the time required for conventional baking. Thus, any defects normally encountered with amylolytic enzymes are avoided. VHF baking permits the processing of flour with abnormally high alpha-amylase activity without the usual crumb-defects. Flours with Falling numbers as low as 95 can be baked without showing the conventionally baked sticky-crumb symptoms. Any shortening of the total baking-time must take place during the initial-phase, since the period after passage through the gelatinization-zone (55-80 G C) is essential for the formation of flavour substances and crust-firming. Notes and references 781

Starch-swelling, allows the amylases to start hydrolysing the substrate, the reaction rate increasing by about 50% every lOoe rise in temperature, remaining active up to 75°e in some cases. Starch degradation, can be due to amylolysis (enzymic), or temperature within the range 100 to 140°C. In both cases dextrins and some maltose are formed, the dextrin fraction increasing by about 15% during baking with flour of normal quality. The rapid inactivation period for cereal alpha-amylase, within the temperature range 68-83°e, is usually traversed within about 5 minutes baking-time. Beta-amylase, is the saccharogenic enzyme, capable of degrading susceptible damaged starch substrates whose free surface has been exposed to attack. Under comparable conditions, the effect of beta-amylase on various starch-substrates yields the following amounts of maltose (in mg): wheat starch (intact) 0-43; dextrin 144'0; gelatinized wheat starch 148; coarse starch fraction 8-4; medium starch fraction 18·0; fine starch fraction 44·0; starch damaged by grinding 127. Glasunow, I. W. (1938) Biochimija Chlebopetschenija (BCh), 1, p.51 (Russian). Glasunow demonstrated that beta-amylase produces 335 times more maltose from dextrin than from intact wheat starch, and even more from gelatinized wheat starch. The relative influences of starch particle-size, and damage by grinding is also clear from his data. Beta• amylase is capable of degrading damaged, susceptible starch during mixing, increasing flour sugars from about 1,5-2,0% to 2·5%. If the dough is bulk fermented (given a floor-time), the maltose level will increase further. During baking, starch degrading and saccharification will continue up until the inactivation range of 57 to noe, which lasts for about 3 minutes only. Starch components of a typical type 550 (0'55% ash) flour, with 90% particles less than 90/lm diameter, consist of a wide selection of damaged and undamaged granules with equally wide ranges of accessibility and susceptibility. Dextrins are formed within the dough-piece mainly in areas oflimited moisture, i.e. the crust• zone, from which, moisture is constantly being removed. Some of these dextrins take part in non-enzymic, non-oxidative caramelization reactions at 140-150oe, contributing to crust formation. Caramelization results from the transformation of sugar-like substances and sugars, under the influence of heat into compounds which vary in colour from yellow to brown. Their flavour ranges from a pleasant caramel, to bitter and carbonized. Some are complex polymers, formed at 150 to 190°C, condensation products and anhydrides.

Proteins during baking on reaching temperatures of 50 to 70 0 e lose their helical structures, beginning to uncoil because of the weaker bonds of the network being broken. Owing to the colloidal nature of protein molecules, they imbibe water, form hydrophilic and hydrophobic bonds, binding sufficient water for starch gelatinization. This gluten-protein binding of water represents about 30% of total dough absorption water, the resulting hydrated protein matrix having small starch granules embedded in it. When the crumb temperature reaches about 60- 70 oe, protein denaturation takes place, leading to eventual coagulation at about 90 0 e (see Fig. 109). At about 74°e, thermal denaturation already transforms the gluten network films, enclosing the gas vacuoles, into a more rigid structure, and this, together with the swollen starch, forms a firm but elastic crumb. Thermal expansion of the gas-cell membranes results in the viscous starch granules within the membrane-wall elongating, the gluten films becoming progressively thinner, eventually rupturing. However, before this occurs, starch-swelling and rigidity has taken over the structural role. At the protein denaturation temperature range 50- 70 o e, the molecules release most of their bound-water, and in so doing, become transformed from a viscoelastic state into that of a plastoelastic solid.

Protein solubility changes during the dough-piece temperature rise from 20 0 e to 900 e were researched by Popaditsch and Falunina in the USSR in 1962. 782 Handbook of breadmaking technology

Popaditsch, I. A., and Falunina, S. F. (1962) Chlebopekarnaja i konditerskaja promyschlennost (ChKP), 2, 1. Influence of heating-up of fermenting wheat-dough on the activity of the proteolytic enzymes. Their conclusions were that the water-soluble fraction of dough-proteins change little from dough to bread, between 20 and 90°C. However, the fraction soluble in O·lN acetic acid, expressed as soluble nitrogen, decreased from 14·2mg/g dry matter at 20 0 e to 6·1 mg/g dry matter at 90°C. This is a measure of the protein denaturation process of the gluten-forming proteins. Significantly, within the temperature interval 60 to 70oe, the water-soluble fraction increased from 5·4 mg/g dry matter to 7·1 mg/g dry matter, owing to the activity of the proteolytic enzymes. Within the same temperature interval, the O·lN acetic acid soluble dough-protein fraction decreased from 13·8 mg/g dry matter to 8·9 mg/g dry matter, falling to 6·1 mg/g dry matter on reaching 90°C. Thus confirming a progressive denaturation of the gluten-forming proteins. Although the critical temperature range for proteolytic enzyme inactivation is between 60 and 70oe, traces of its activity were detected in the crumb as high as 85-90°C. The Fig. 111 schematic indicates the dough-protein cleavage sites, designated ---E, at which the dough-proteinases become active during the baking process. Protein-coagulation and starch-gelatinization together form the porous structure of the baking dough-piece, and finally that of the loaf-crumb. The rheological properties of the bread-crumb are quite different from that of the dough from which it was transformed. Deformation modes ofthe baking loaf-crumb of wheat and rye breads of various weights, from flours of various extractions have been studied by several researchers during the period 1959- 69 in Hungary, the USSR and the GDR (see Figs 110 and 112). Auerman, L. J., and Melkina, G. M. (1967) NT/nf, 15, 6 (Russian). These workers used specialized equipment to study the changes in bread-crumb elasticity at 10- or 20-minute intervals during baking for a total time of 60 minutes. Other parameters measured were: plastic deformation; and elastic deformation expressed as the difference between the total and residual deformation; relative-elasticity being expressed as a percentage of total deformation. Bread samples of various weights, and from flours of various extraction-rates were included in these studies. Graphical plots ofrelative-elasticity% versus baking-time, indicate certain correlations between flour extraction rates and relative crumb• elasticity of both wheat- and rye-flour breads. The higher extraction flours show relative• elasticity rising to a maximum limiting value, and then falling-off, whereas the lower extraction flours show continuous rises in relative-elasticity of the crumb during the baking process. This phenomenon is considered to be a function of enzymic content of the flours, involving both the starch/amylase, and the protein/proteinase complexes during the warming-up period. Other covariables are: dough water content, dough pH, and the temperature and rapidity of the heat-exchange process. Dough water absorption, when increased, tends to lower the temperature optimum of the flour enzymes. Speed ofwarming-up of the dough-piece is crucial to enzyme-inactivation. The more rapid the warm-up, the higher the inactivation temperature of the enzyme complexes. Popaditsch,l. A., and Falunina, S. F. (1962) ChKP, 2,1 (Russian). The influence of the heating• through of the fermenting wheat dough on the activity of the proteolytic enzymes. Results obtained by these workers indicated that for a wheat dough of 48 % water-content, at pH 5·8, the temperature optimum for the wheat proteinases lies between 60 and 70oe, always depending on the dough warming-up process. Increasing the water-content of the dough to 70% had the effect oflowering the temperature optimum of the enzymes to 50°C. Popaditsch and Falunina found that the nitrogen fraction soluble in 0·1 N acetic acid, indicative of dough• protein denaturation at different temperatures, decreased progressively from 55·9% at 20 0 e to 24·0% at 90°C. Proteinases are proteolytic enzymes capable of degrading true, complex protein molecules Noles and references 783

into lower-molecular-weight derivatives, i.e. polypeptides, peptides and peptones, attacking the CO-NH peptide linkages. Peptidases then complete the hydrolysis to the amino acid stage. Both proteinases and peptidases occur naturally in wheat, being mainly concentrated in the germ and bran fractions. Endopeptidases attack the internal sites of the protein chain, whereas exopeptidases attack peptide linkages joining terminal amino acid residues, thus producing amino acids as end-products. Cereal proteinases appear to be most active at pH 3·8 to 4·5, but this varies with temperature and the substrate-structure. Their activity is difficult to measure with any accuracy, but the most widely used procedure is to prepare an extract and a suspension from about 109 of sample with a O·lM acetate buffer at pH 3·8. After centrifugation, the proteinase-activity is determined in both the extract and the residual suspension by reaction with a suitable substrate, e.g. haemoglobin, azo-dye derivatives of gluten or casein. After precipitation with trichloroacetic acid, the soluble-nitrogen released can be determined according to KjeIdahl, or determined colorimetrically using Folin• Ciocalteau reagent. A suitable calibration-curve being prepared with appropriate dilutions of a standard tyrosine solution. Proteinase activity is expressed in tyrosine-equivalents per gram of sample. Reagent-blanks and about 8-10 parallel samples of the test material are recommended for precision-improvement. Loaf-crustformation due to 'browning' effects are both enzymic and non-enzymic processes. Enzymic ones are due to the formation of the light-yellow to black coloured dextrins. Non• enzymic browning results from the Maillard and melanoidin reactions, of great importance for the synthesis of colour and aroma substances, from carbonyl and amino acid groups. The high-molecular-weight melanoid ins forming from reactions between sugars and nitrogenous substances. Typical nitrogen sources can be amino acids, polypeptides, proteins, amines or ammonium salts. Sugars can also be replaced by similar compounds with reactive aldehyde groups. Reaction speed of meIanoidins will depend on the control of temperature, pH, moisture-content of the dough, and the adequate presence of free amino-groups and aldehydes in a reactive form. Longer and more intensive mixing-times will open up and expose the free reactive groups of the protein molecule. Careful control of baking time, heat distribution and heat-transfer, ensure the optimization of meIanoidin formation and loaf browning. For the formation of a good crust colour adequate sugars and protein, coupled with the presence of humidity (injected-steam) are essential. These conditions are ideally achieved by dough fermentation with careful control of temperature, time, dough• consistency, dough-pH, and balanced formulation of ingredients. Bread/favour and aroma, is also the result of the formation of melanoidins, often referred to generally as the 'Maillard reaction'. The many possibilities of reactions between the various nitrogenous groups and free reducing sugars have been the subject of much research, mainly concerning the complex pathways and intermediates involved in forming the actual flavour compounds. Hodge, J. E. (1953) Agr. Food Chem., 1, p.928. Hodge, J. E. (1955) Carbohydrate Chemistry, 10, p. 169. Namiki, M., and Hayashi, T. A. (1983) In The Maillard Reaction in Foods and Nutrition, edited byG. R. Waller and M. S. Feather,ASC Symposium Series 215,ASC, Washington, DC, USA. Lane, M. J., and Nursten, H. E. (1983) ASC Symposium Series 215, Washington, DC, USA. Melanoidin reactions of the Maillard system, according to Hodge, involve initially reducing sugars and amines condensing to form addition compounds, i.e. amine-group and carbonyl• group from the sugar. This is followed by removal of one molecule of water (dehydration), to form an N-substituted glycosylamine. Isomerization then occurs (Amadori rearrangement), forming 1-amino-1-deoxy-2-ketones, which remain in equilibrium with their enol forms (1,2- enol forms). All reaction products up to this point are reversible, and colourless. The intermediate products of Amadori rearrangement then undergo various reactions depending on prevailing conditions. Under neutral or acid pH, they can either lose water to form a ring compound (Schiff's base) hydroxy-methyl-furfural or furfural, or eliminate an amine group to 784 Handbook of breadmaking technology

form a methyl alpha-dicarbonyl compound. The former are colourless reductones, and the latter brown fluorescent substances. Alternatively, carbon dioxide can become split off from amino acids to form an aldehyde (a Strecker degradation process), the latter being either colourless or yellow. Final reactions involve dehydration, resulting in the formation of dicarbonyls, which then condense or become polymerized, forming various melanoidins varying in colour, taste and aroma intensity. Thomas, B., and Rothe, M. (1960) Baker's Digest, 34, 4, p. 50, studied model systems involving the Maillard reactions to establish a correlation between starting materials and end-products. Reactivity of the monosaccharides and amino acids in the Maillard reaction are variable, and can be detected by the relative increase in furfural content and crust-browning. The most reactive sugar is the pentose xylose, and the most reactive amino acid isoleucine and leucine. Maillard reactions are more significant for bread-aroma formation than caramelization• reactions, the latter only taking place at elevated temperatures. Pyrazines, as bread-aroma components have been widely reported. Possible reactants for their formation are amino acids, diketones and ketoaldehydes. Many aldehydes formed in the crust diffuse into the crumb interior of the loaf during cooling, and become absorbed. Flavour substances can also become locked into the amylose starch fraction during cooling. Full breadjiavour development depends on the availability of free, reactive amino acids, sugars and alcohols. Their presence is a function of enzyme activity, and the degree of polymerization and hydration of their substrates from mixing to baking. A good balance between starch/amylase, and protein/proteinase activities, especially in the case of wheat• flours will produce an end-product of appetizing flavour. Intensification of flavour and aroma can be achieved by: 2 hours or more final-dough fermentation in bulk; the use of solid or liquid pre-ferments (sponges or brews); the application of biotechnology, by the careful addition of specific enzymes; or the use of a biologically active mixture to stimulate yeast activity and fermentation. Most important of alI, however, is oven control, and the formation of at least 3 mm of crust in the case of a I-kg 10ng-rolIed hearth white loaf, and at least 4·5 mm of crust for a I-kg rye or rye/wheat, hearth-baked, 10ng-rolIed loaf. Volatile/favour and aroma components, such as alcohol, diacetyl and iso-aldehydes tend to progressive evaporation during baking. Less volatile flavour substances, e.g. iso-alcohols, acetic acid, pyruvic acid, acetoin, butylene glycol, ethyl lactate, acetaldehyde, iso-valeric aldehyde and furfural (formed during baking with pyruvic-aldehyde, the latter being more volatile), tend to be retained, and diffuse through the crumb during cooling, becoming either absorbed, or locked into the starch amylose fraction. LOlI'-volatility/favour and aroma components, which include the melanoid ins formed within the crust, dihydroxyacetone, ethyl succinate, lactic acid and succinic acid, are components which form the basis of the typical bread flavour and aroma.

Fermentation duration and the use o.lpre~lerments encourage the formation of flavour and aroma substances in bread. Rothe, M., et al. (1972) Nahrung, 16, 5, p.507. Shortened process for white bread and its influence on bread aroma I. Carbonyl compounds and alcohol (German). Rothe et al. compared the influence of different dough-processes on the alcohol content of the resultant bread. In general, during the first 20 minutes of baking, there is a rapid loss of alcohol within the chamber, falIing from over 500 mg/IOO g bread to about 400 mg/IOO g. Using conventional mixing and fermentation procedures, about 31 % of the alcohol produced during fermentation was found to have evaporated during baking, compared with about 60% when using intensive-mixing and shortened processing. Other volatile alcohols such as: n• propanol and Iso-butanol also disappear at similar rates, depending on the dough-process. Rothe, M. (1966) Bread aroma determination, Brot und Gebiick, 20, 10, p.189 (German). Rothe, M. (1974) Bread aroma. In Handbook ol Aroma Research, Berlin: Akademie-Verlag, Berlin, 1974 (German). Notes and references 785

The significance oflonger fermentation-times was confirmed by Coffman, who isolated much higher levels of amyl alcohol from bread made by a straight (direct) processed dough, than could be obtained from bread prepared from a continuous, sponge or short-time dough process. Coffman, R. (1964) Cereal Science Today, 9, 7, p. 306. The aroma of continuously mixed bread. It is the author's own experience that straight-processed doughs made to stand for 10- 12 hours overnight, compared with those processed over 2-3 hours, show much higher concentrations of aroma substances in general, amongst which the predominance of amyl alcohol in tbe fermentation gases is very marked. However, on baking into bread, the sensory perception of both flavour and aroma appears to change in favour of volatile organic acids, acetic acid predominating, with background notes oflactic and succinic acids. The diversity of bread flavour and its complexity is made clear by Coffman in a 1967 publication. Coffman, J. R. (1967) Bread flavour. In The Chemistry and Physiology 0/ Flavours, edited by W. H. Schulz., E. A. Day and L. W. Libbey, AVI Publishing Co., Westport, CT, 1967. Kretovich, V. L., et al. (1988) Prikl. Biokhim. Mikrobiol., 24, 2, p. 207-10, at the Bach A. N. Institute of Biochemistry in Moscow, observed appreciable losses in free lysine, leucine, valine, and the monosaccharides arabinose, xylose, galactose and glucose during the baking of rye bread, owing to involvement in melanoidin reactions to improve bread flavour and aroma. Enrichment of the doughs with condensed, fermented whey at 9% increased bread amino acid levels by about 20%. The enriched bread containing much higher levels of isopentanal and isobutanal, which are formed from leucine and valine respectively, together with other aroma compounds, than was the case with non-enriched bread. Johnson, J., and Linko, Y. (1964) Analysis of bread-flour components. Qualitas Plantarum et Materia Vegatabilis, 11, 2, p.256, draw attention to the significance of the breadmaking process on the formation of carbonyl compounds in the crust and crumb. Their results indicated that the use of a pre-ferment-sponge provided the highest level of carbonyls generally (crust 29·8, crumb 3·0mg/l00 g). The liquid pre-ferment produces 25·7 and 4·0mg/ tOo g in the crust and crumb respectively. However, the levels of furfural, hydroxymethyl• furfural, acetone and proprionaldehyde were all significantly higher in the pre-ferment• sponges. Carbonyl compound/ormation in bread is strongly influenced by the baking procedure. The bread variety pumpernickel, which has a very long maturing-time, and a prolonged baking• time in pans at relatively low temperatures, contains far more furfural in the crumb than other bread varieties baked from the same flour. F/our-type and extraction rate also influence the formation of furfural, acetaldehyde, and other aldehydes, as established by Rothe and Thomas. Rothe, M., and Thomas, B. (1965) Differences in aroma profile of rye-bread, wheat-bread and mixed wheat/rye bread. Ref Konf Miedz. Zytn., 4 (German). Less volatile alcohols, amyl and iso-amyl alcohols, iso-butanol, iso-propanol and propanol, although only present in trace amounts, have a potent influence on the flavour profile of wheat breads. Products ofyeast fermentation, such as acetyl methyl carbinol and dihydroxyacetone, act as precursors in the formation of flavour components of fresh bread. On oxidation, the former yields diacetyl, but straight doughs are deficient in acetyl methyl carbinol compared with sponge and liquid pre-ferments, and diacetyl formation depends on the presence of adequate concentrations of sugar and oxidants. Dihydroxyacetone reacts thermally with proline yielding substances associated with crust-odour. Wiseblatt, L., and Zournut, H. (1963) Cereal Chem., 40, p.116. Organic acidformation during fermentation, especially acetic and lactic acids help to catalyse the rearrangement of the condensation products formed from amines and reducing sugars in the Maillard reactions during baking. 786 Handbook of breadmaking technology

Measurement of bread-crust surface colouration continuously during the baking-cycle has been developed in the USSR. Telitschkun, W. I., et al. (1968) Colouration of the bread-surface during baking. New Developments in Oven Technology, Zinti, Moscow, p.47 (Russian). The change in light intensity reflected from the bread-crust during baking is continuously monitored and recorded with a potentiometer./A beam of/light impinging on the dough• surface is reflected, and is measured on the scale of a photocell. Colour-intensity changes are measured as percentage reflection during baking, concurtently with loaf-surface temperature, both parameters being plotted against baking-time. On setting in the oven, the reflectivity of the dough-piece falls rapidly owing to surface starch-granule gelatinization, reaching a minimal reflectivity coefficient (%) when the surface-temperature reaches 60DC, i.e. the starch gelatinization range. Further temperature rises result in progressive increases in the reflectivity coefficient, as the surface becomes lighter in colour owing to drying out. On reaching 100DC, the melanoidin reactions commence, the crust taking on a progressively darker colour, causing the reflectivity coefficient to fall sharply. On reaching the range 130 to 170DC, loaf surface colour changes from light-yellow to dark-brown, and above 170DC progressive carbonization occurs. The application of this equipment allows the optimal conditions for an ideal crust-colour to be ascertained, and then controlled, which contributes to the full automatic control of the baking-process. Rooney, K., Salem, A. and Johnson, J. (1967) Cereal Chern., 44, p. 539. Studies of the carbonyl compounds produced by sugar-amino acid reactions I. Model systems. Working with sugar/amino acid mixtures in buffered solutions at pH 5'5, heating at 9YC for 12 hours, these researchers identified various carbonyl compounds produced from the sugars: glucose, maltose and xylose. It was found that xylose gave the most intensive colour with amino acids in the melanoidin reactions, measured at 500 nm. This correlates with the more intensive crust and crumb colour development in rye bread versus wheat bread, owing to the presence of larger concentrations of pentoses. Also, pentose sugars are not fermented by baker's yeast strains. Aldehyde carbonyls formed during these reactions relate to the amino acid present, rather than the type of sugar participating. However, the type of sugar has a strong influence on crust-colouration. Research into Maillard-browning, as applied to bread formulations, requires careful experimental design on the part of the researchers. In the case of wheat bread, a straight• dough process with added saccharose at 3·0% is appropriate to provide adequate basic substrate for the yeast, coupled with an Arkady-type improver. The dough can then be fermented for 2 hours in bulk, allowing a 20-minute recovery, followed by final moulding and proofing for 55 minutes, baking at 220DC for 30 minutes. The amino acid variable can be premixed with the standard sugar in solution form (0'02M amino acid :0'02M standard sugar), being added to the formula prior to mixing. Changes in crust-colour can be measured with a reflectometer, similar to that designed by Telitschkun et aI., cited previously. A green filter can be utilized, and readings taken from three loaves of a sample batch, using an average of 10 readings from each loaf. Isolation and identification of the carbonyls, as 2,4-dinitrophenyl• hydrazine (DNPH) derivatives, can be carried out using GLC, TLC or PC techniques. Quantitative estimation can be accomplished by extraction and UV-absorption, expressing data as milligrams of free carbonyi/l 00 g of crust or crumb. Furfural concentrations in both crust and crumb, can be determined by the procedure of Linko. Linko, P. (1961) Anal. Chern., 33, p. 1400-3. Hydroxymethylfurfural concentrations can be determined by extraction from the ground crust or crumb with benzene, followed by centrifugation. Combined concentrations of these aldehydes can also be determined by the method of Linko. These aldehyde Maillard reaction products, however, only represent intermediates, which, in the presence of available free amino acids, undergo further condensation forming polymers. Therefore, reduced levels of the aldehydes can be expected where free amino groups persist, and their concentrations are lowest in bread-crust with otherwise large amounts of carbonyl compounds. Although bread Noles and references 787

flavour and aroma can be modified by amino acid addition to formulations, the optimal end effect of the total flavour experience requires a balanced ratio of a complex blend of aromatic compounds, their simultaneous effect on the sensory organo-receptors, and the trans• mission of their impulses to the central nervous system. Routine bread flavour evaluations tend to fall into the sensations of being: sweet, salty, sour, and bitter. Sour tastes are due to the presence of various organic acids. Lactic acid is the most important contributor to taste, followed by malic, tartaric, acetic and citric acids. Acidic odours are due to acetic acid, followed by lactic, malic and tartaric acids. Acetic acid gives a pungent impulse to the sensory organs of smell, requiring careful control when wheat and rye bread is prepared from liquid-yeast cultures, firm or liquid sours, and pre-ferments. Appreciable differences in taste and smell can be detected by a trained taste-panel using the Triangle-test. This requires the panellists to identify the odd sample from three, two of which are identical. Its success depends on the sensory-amplitude of detection or sensitivity of the members of the panel. Accurate quantitative analysis of the components of taste and smell are conducted by placing the product in a flask and freezing with liquid-nitrogen at - 196°C, under a vacuum of 1 mm mercury. The sample is then allowed to warm up to room-temperature, and the volatile liquid condensed. The condensate is then subjected to GLC for identification, and quantitative determination of the volatile components. Breadmaking process evaluations versus bread flavour and aroma demand an exact determination whether any derived improvement in flavour and aroma substances take place during the pre-ferment, dough or baking stages. Typical process variables are: solid-sponge, liquid pre-ferment, straight-dough, short-time mechanicaljchemical maturing procedures; rye sour-dough processes using three-stage sour-builds, Berliner short-sour, or continuous liquid sour-dough processes. Examples of research procedures involving such studies are the following: 10hnson, 1., Rooney, L., and Salem. A. (1966) Advances in Chemistry, 56, p. 152. The chemistry of bread flavour. Rothe, M. (1970) Influence of technology on the flavour of rye bread. Report 5: World Grain and Bread Congress 1970, Vol. 5, p.203 (German). Rothe, M. (1965) Differences in the aroma content of rye bread, wheat bread and mixed rye/wheat bread. Ref Konf Miedz. Zytn., 4 (German). 10hnson, 1., and Miller, B. (1956) 1. Agric. and Food Chem., 4, p. 82. The effect of fermentation time on certain chemical components of pre-ferments used in breadmaking. Rubenthaler, G., Pomeranz, Y., and Finney, K. F. (1963) Cereal Chem., 40,6, p. 658~65. Effect of sugars and certain free amino acids on bread characteristics. Hunter, 1., et al. (1961). 1. Food Sci., 26, 6, p. 578~80. Volatile organic acids in pre-ferments for bread. Tokarell'a, R. R., and Kretouich, V. L. (1963) Tr. Tsentr. Nauchn. Issled. Inst. Khlebopekar Prom, 9, p. 95~9. Effect of enzyme preparations on the accumulation of reducing sugars during dough-handling and on the aromatic complex of bread. Tokarewa, R. R., and Kretovich, V. L. (1963) Acid. Sci. USSR, MoscoII' Proc. Internat. Congr. Biochem., 5th Moscow, 1961. The use of concentrated enzyme preparations from fungi in breadmaking.

CHAPTER 3.3 ENERGY SOURCES, TYPES OF OVEN AND OVEN DESIGN

Heat-energy sources for the baking of bread can be derived from: wood, brown coal briquettes, peat, fuel oil, natural gas, manufactured-gas (town or city gas), anthracite, coke, bituminous-coal (hard/mineral or pit coal), or applied as electro-energy. The net heating effect 788 Handbook of breadmaking technology

of these energy-sources is similar, choice depending on local availability and cost. In areas remote from industry, wood, peat or mineral-fuels could be the most economic choice. The final choice will depend on which resource is naturally available, and economically viable, also its relative efficiency and ease of control in the bakery. In many European countries, natural gas has become the final choice for both the tunnel-ovens in industrial bakeries and the batch-ovens used in smaller bakeries. The relative efficiency, or exploitation, ofenergy sources varies considerably. Coal-heating is about 20%, gas 50%, being maximal in the case of a directly heated electrical oven, which is 85% efficient. Calorific value, is a measure of the heating-capacity of any energy-source which produces heat of combustion. It is defined as the quantity of heat in kilojoules, liberated by burning 1 kg of a solid/liquid fuel, or I m3 of gaseous fuel. Heat ofcombustion and calorific value, are differentiated by the liberated heat of condensation when steam condenses. calorific value = maximum heat of combustion - 2260 W A where WA is the water-vapour in the exhaust-gas in kg/kg of fuel, 2260 being the heat of condensation in kJ water/kg-I (nearest whole number). The appropriate units are: kJ m- 3 for gaseous fuels, and kJ kg-I for solid fuels. Examples of calorific values and heats of combustion are: natural gas (90% methane) 33 600 and 37400; city gas 14250 and 15950; gas from brown-coal 15500 and 16800; fuel oil 42000 and 44100. Heat production for baking, depends on the following basic principles: Exothermic reactions involving the burning of coal, natural gas, manufactured gas, or fuel oil, the oven-chamber walls dissipating heat-energy as radiant-heat and conductive-heat into the chamber atmosphere. A mains power-system heating an electrical resistance, controlled by a temperature sensor, emitting diverse spectral waves, extending into the bright infrared range, amounting to over 40% relative to solar-energy at 100%. High-frequency (H F) electromagnetic waves, including wavelengths within the bright and dark infrared range between 3 x 1011 and 4 x 10 14 Hz, maximum emissive-energy of the latter being at about 3 x 10 - 4 cm, representing only 20% compared with solar-energy, owing to the longer wavelength. The bright, shorter wavelength infrared frequencies penetrate deeper into the dough-piece, shortening the baking-time. Dielectric heating involving the application of a high-frequency electromagnetic field, whereby the dough-piece is subjected to a rapidly alternating electrical field, generated by a magnetron (HF generator). The dough-piece acts as dielectricum between HF-electrodes, which act as capacitor-plates, thus setting up an electric-dipole system. The rapidly alternating field results in a high frequency oscillation of the dipolar water molecules, causing the product to heat up uniformly from within, instead of relying on an external heat-flux and penetration. Equipment for dielectric heating operate within the frequency ranges 10kHz to 500 kHz, or 13 to 27 MHz. The oven-mesh or steel-band of a tunnel-oven can serve as the lower electrode for continuous-baking processes. Since HF/dielectric baking cannot produce a crust, it must be combined with conventional radiation. The most effective combination is HF/IR radiation, as suggested by Professor E. Maes. Maes, E. (1964) Fermentativ, 26, 5. In Bulletin de ['Ecole Official Meunerie Beige, 1964, p. 203 (French). Using the HF/IR oven type 'Reforma', Maes found certain advantages compared with conventional ovens, viz. 50% reduction in baking-time, a 6-7% increase in loaf-volume, and crust control by using IR-radiation units. However, certain inherent disadvantages have to be overcome. Recent research by Salovarra et al. in Finland has shown the versatility of its application for baking high-amylase flours. Notes and references 789

Salovarra, H., et a/. (1988) Acta Alimentaria, 17, 1, p. 67-76 (English). High-amylase flour in baking with high-frequency (VHF) energy (EKT Dept. Food Tech. Univ. Helsinki, SF-0071O Helsinki, Finland). Fuel-efficiency depends on its purity, the relative weight of carbon and hydrogen it contains (hydrogen content increases its calorific value), and an adequate supply of oxygen to ensure optimal combustion. Heat-energy utilization, can be maximized by careful oven design, and control of unnecessary sources of heat-loss, e.g. unrestricted feed and discharge-point opening. Typical examples of net heat-utilization for a wire-band tunnel-oven are: heat-energy input 100%, net heat• utilization 45%; exhaust-gas losses 35%, humidity heat-loss 12%, radiation losses 8%, according to Schwate and Ulrich. Schwate, w., and Ulrich, U. (1986) In Special Processes in Baking-A Process Manual, VEB• Fachbuchverlag, Leipzig, GDR. A more detailed breakdown of heat losses is given by Schneeweiss and Klose. Schnee weiss, R., and Klose, O. (1981) In Technology of Industrial Baking, VEB• Fachbuchverlag, Leipzig, GDR. Theoretical input levels of heat required to bake a I-kg loaf have been cited as 530 to 630 kJ kg - \ and for a l-Ib loaf as 325 to 400 Btu. Such data is only a guideline, and will depend, amongst other variables, on the specific-heat levels of the dough, e.g. 2·6-3·0 kJ kg- 1 K - I for lean doughs, and 0,65-0,88 for enriched lower density formulations. Actual heat-input measurements indicate that ranges of 330 to 400 Btu per pound of bread are more realistic, compared with 1000--2000 Btu for the older coal-fired brick-ovens using a peel. Oven capacity is often expressed by the baker as pounds, or kilograms of bread per hour, whereas the oven-manufacturer may express it as pounds of dough per square foot of baking• surface per hour, or more simply as baking-surface in square metres. Relative oven heat-utilization guidelines, expressed in fuel/lOO Ib bake and Btu/lb of bake for the various types of oven have been compiled by Harrel and Thelen. Harrel, C. G., and Thelen, R. J. (1959) In Conversion Factors and Technical Datafor the Food Industry, edited by Harrel and Thelen, Burgess Pub I. Co., Minneapolis, MN. Their data clearly indicate that direct-fired tray-ovens produce the highest heat-utilization per pound of bake, irrespective of the choice of fuel, and that electro-energy offers the lowest Btu/lb of bake for all common oven-types. Manufactured gas and natural gas being the next best all round choice of energy-source for most ovens.

3.3.2 Types of Oven and Oven Design Choice of oven type will depend on such considerations as: bakery production-throughput capacity, product diversity, available floor-space, energy source, economy in operation, construction and maintenance. Early commercial oven designs were known as side-flue peel-ovens, or peel brick-ovens, consisting of large chambers of brick construction. The floor or 'sole' being of large square refractory tiles, and the crown arched, with the fire-place or furnace (long and narrow in shape) positioned obliquely to feed the flames over the crown, and around the chamber, before passing out through the flue to the left of the oven-mouth. A combination of coal and coke gave the best heating effect, the latter requiring a deeper fire-bed, and more draught or secondary-air supply. Their massive construction, integral with the bakery, allowed the storage and delivery of a solid bottom heat, and a steady radiant top heat. Such conditions were conducive to an excellent bake, producing bread with an appetizing crust and crumb flavour and aroma. Operation of these ovens, however, demanded skill and experience, coupled with good judgement on the part of the master-baker, to achieve consistently even• baked products. Regular stoking and raking of the fire-bed ensured an efficient combustion, 790 Handbook of breadmaking technology without any cold-air blowing through. The baking technique was to attain a temperature of 550 0 P (288°C) by constant firing, setting the batch in the oven with long-handled wooden 'peels' of various sizes as rapidly as possible. After setting, the pyrometer would normally register about 500 0 P (260°C), owing to the presence of the relatively cold load. After a residence-time of about 1 hour, the bread was unloaded with the peels. During this time, the oven conditions had reached a 'steady-state' due to the stored heat, having a temperature suitable for baking smaller fermented products and confectionery items. The early German ovens were similar in design, depending on direct heat-transfer from the fire-place to the oven-chamber and brickwork. Such ovens depended on heat-storage, the temperature of the tiles and brick walls falling as the products are baked. Steam retention was often achieved by building the hearth or sole with a slight gradient. The high initial temperature, and even heat release made these ovens ideal for baking all types of rye and wheat breads. The introduction of the drawplate-oven, whereby the hearth could be withdrawn from the chamber on wheels running on tramlines, allowed all products to enter and leave the chamber simultaneously, instead of the first-in/last-out situation of the side-flue peel-oven. However, these ovens required a large work area, and. suffered a large heat-loss at loading and unloading. The invention of the Perkins steam-tube led to the development of the steam-oven. Such ovens depended on heat-transfer through a liquid medium, with which the tubes or pipes were filled. The tubes were located beneath each chamber floor (sole), running parallel, about 10 tubes serving each deck. The tubes were usually heated by solid fuel or gas, extending into the furnace to acquire the initial conductive heat. Modern ovens can be classified into batch-ovens, which are suitable for small to medium size bakeries, or industrial bakeries with a specialized product range, and larger capacity continuous industrial baking ovens. Batch-ovens depend on a hot-gas circulation system (cyclothermal) from electrically heated elements. Very few ovens are still directly fired with solid fuels, or indirectly heated with the Perkins steam-tube. However, one should not assume that older oven-heating technologies are completely obsolete, since the end-product quality from such ovens was excellent, although more variable in character. Independent of the heating principle involved, most batch-ovens (Fig. 113) tend to be multi-deck in design, with the exception of rack-ovens, which employ racks with trays, either fitted with wheels or running on tracks. Typical multi• deck ovens have 4~5 decks, with total baking-surfaces of 9 to 19 m2, the temperature of each deck being independently controllable, enabling the baker to bake various products simultaneously. Such ovens allow throughput capacities of 120 to 240 I-kg long loaves, or 800 to 1600 round bread-rolls at 50 g. Using oven 'setter' equipment (German: Abrollapparate), I-setter width 600mm, 2-setter width 1200mm, 3-setter width 1800mm, and 4-setter width 2400 mm, loading can be rationalized. Reel-ovens, the first mechanical oven design, are of American origin being still found in bake• shops in the USA. They were built like a ferris-wheel, the reel-structure revolving vertically about a horizontal axis within the baking-chamber, supporting baking-trays, hung from hanger-pins protruding from the large wheels inside the oven. Rack-ovens offer a more expedient solution for the batch production of a diverse range of products. They consist of a vertical chamber into which the special racks are wheeled, carrying up to 100 trays of product. Usually, the racks are clamped onto a turntable, which rotates during the baking cycle, thus ensuring convective heat-transfer to the products. The Static Radian~ Rack Oven manufactured by Gouet of Prance (marketed in the UK by EPP Ltd of Banstead SM7 2NT, UK), produces very solid heat characteristics, and much less heat loss, thus combining the baking quality of a deck-oven with the ease of operation of a rack• oven. This oven is energy efficient, the oil-filled radiators above and below each tray of products, providing a unique convection system, heating from cold to bake within about 20 minutes. The thermal heating fluid is circulated and heated by remote heat-exchanger and Notes and references 791

pump unit. Steaming facilities are also provided. Such ovens are very popular for in-store bakeries, and craft bakeries with a mixed trade. Industrial-baking ovens, are designed for continuous production, and are often referred to as 'travelling-ovens'. The travelling tray-ovens ojsingle-lap or double-lap design, are illustrated in Figs 114 and 115 respectively, being a development of the reel-oven in the USA. Single-lap models provide one passage through the oven's two heat-zones, as shown in the schematic, loading and unloading taking place at the front end. With automatic loading and unloading equipment added, this oven increased in popularity, the single-lap design offering a simple operational performance with one horizontal run, and a lower crown for steaming. Modulation heat control ensures lateral heat control and rapid response to loading changes. The number of trays vary from 18 to 74, production capacities ranging from 2500 to 8000 Ib bread/hour. Double-lap models are based on the same design principle as the single-lap, but the trays travel through four heat-zones instead of two. The vertical crown height is twice that of the single• lap, but the floor-area required is much less, which is important where floor-space is limited. Construction and duct work is more complex with the double-lap models, steaming and zonal heat control being more difficult owing to stacking. Most models are direct gas-fired, with automatic oven-loader, accommodating about 48 trays on average. Double wire-band return-ovens (German: Doppelnetzband-RiicklaujoJen), to be found on the European continent, are also based on a double-lap principle, but consist of two wire-bands in the form of endless conveyors, running parallel, but within two separate oven-chambers (see Fig. 116). This design offers a saving in labour, with the help of mechanical transport of the dough-pieces from the oven-mouth onto a desired position on the travelling-band wire conveyors. This transports the dough-pieces the full length of the wire-band conveyors within the oven-chambers, the baked products then being returned to the mouth of the oven, by which time, the baking cycle is complete. The latter operation being achieved by reversing the rotation of the motor which drives the wire-bands. On completion of the full distance in both directions, the motor automatically switches off, but button-switches can override, allowing the bands to be halted in any position. This combines the advantages of the multi-deck oven, i.e. limited floor-area and good heat utilization, with the ease of loading of the wire-band tunnel-oven. The baking-surface is mobile, and part of the travelling-band protrudes outside the oven-mouth, allowing the dough-pieces to be deposited directly onto the band. Most of these ovens are gas-fired, using the indirect hot-gas cyclothermal heat circulation system. The baking-surface of each chamber is 6·60m2 , making a total of 13·20m2 . Throughput is normally about 216 kg bread/hour, which can be increased to a maximum of 258 kg bread/ hour. Bread-roll output is 4000 units/hour maximum, bread and roll outputs providing improved capacities compared with the four-deck multi-deck oven. The best engineered example of this unique design concept is the DNRO, with 13·2 m2 baking-surface, manufactured by VEB Kombinat Fortschritt, Backereimaschinenbau, Halle, GDR. Wire-band tunnel ovens represent the most technologically and economically advanced baking ovens to date, having a good general thermal efficiency. They are completely continuous in operation, dough-pieces being fed in at one end of the chamber and discharged at the other. Such ovens are eminently suitable for line-production systems, where the baking stage must be synchronized with all previous and following production stages. For European bakery requirements, where a mixed production range of hearth-, panned-, and variety• breads and rolls are produced, and baked in the same oven, the flexibility of these ovens is ideal. However, on the North American continent, for the baking of panned bread and rolls, its economic justification is questionable, on grounds of floor-space versus output capacity. Anderson, R. C. (1973) Baker's Digest, 47, 2, p.28. Anderson points out that a tunnel-oven of output capacity 8000lb of bread/hour requires about 1000 ft2 more floor area than a single-lap oven of comparable capacity, when both are 792 Handbook of breadmaking technology

equipped with automatic loading and unloading equipment. General features of wire-band tunnel ovens are a long, low baking-chamber, within which a motor-driven conveyor carries the oven-hearth in a straight line for stretches of 100 to 400ft (30·5 to 121·9m). The length being divided by baffles into one or more steaming zones, and up to eight heat-zones of 30-60ft (9-18m) each, depending on specification (see Fig. 118). Each zone has its own individual control, made easier by separate controls for top and bottom heat, and lateral heat balance. Steaming conditions are easily optimized, without the stabilization problems of swing-tray ovens. An example of such an oven is the Duotherm wire-band oven type DUO-NU, manufactured by Werner & Pfleiderer, 7000 Stuttgart 30, FRG. This oven unit is applied to the baking of all types of product: panned-bread, hearth- and variety-breads, bread-rolls,

cakes, bases, rusks, pizza and panettoni. The .Duotherm I forced convection heat-transfer system in the rear part of the chamber can be applied for specific products, providing even browning and crust formation on the sides of panned products, shorter baking-times, and a thicker crust on free-spaced hearth products. At the feed-end-the location of the burners• the heat circulation system is cyclothermal, the rear section of the chamber being fitted with the Duotherm forced convection system. This involves feeding the heating-gases for top and bottom heat into the numerous ducts, distributed across the width of the Duotherm radiators. The baking-chamber atmosphere being circulated in a vertical direction by a reversible fan through the spaces between the ducts. In this way, improved heat-transfer, on a convective basis is achieved by rapid air circulation around the products, e.g. side-walls of pans or hearth products not easily reached by infrared radiation. The direction of flow being switched up or down, or terminated by a switch on the control-panel. The indirect cyclothermal heating system depends on the combustion-gases, or hot air from electrical heating, being circulated through ducts around the baking chamber, having no contact with the products. The ducts are of steel-sheeting, and the oven sole of chamotte or brick-tiles, steel-plates, or a wire-mesh band. Owing to ease of regulation, gas or oil are mainly used, but with electrically heated air, a closed circulation system can be used. Cyclothermal heating systems are used in tunnel-ovens, multi-deck ovens, double wire-band return ovens (DWRO), and rack-ovens (see Fig. 118). Wire-band tunnel-oven heat distribution is achieved by dividing the chamber into individual baking temperature control zones, allowing control of top and bottom heat independently of one another (see Fig. 119) The conveyor element within the chamber can be endless wire• bands, steel-bands, metal-plates or metal-plates covered with chamotte, which permits the user to label his bread 'brick-oven baked'. The source of energy is gas, which after combustion, is distributed by means of the cyclothermal system through heating-ducts positioned above and below the oven-chamber, as shown in Fig. 119 (a) and (b). These heating-ducts acting like a network of radiators. Only part of combustion gases, on leaving the duct network, pass out of the chimney. Instead, most of the 200 to 400°C hot gases are returned to the combustion-chamber, where the burner flame gases mix with it at a temperature of about lOOO°C or more. However, the gases for heating the oven-chamber must not exceed 600°C, otherwise the security fuses melt, extinguising the burner. The burner is so constructed that the recirculated gases simultaneously cool the combustion chamber from the outside. As a result of the partial recycling of the heating-gases, the cyclothermal tunnel oven can utilize up to 50% of the energy-input. Oven-capacity depends on the band conveyor width and length, dimensions of the bread-pan straps, hearth-loaf spacing, or tray dimensions. Wire-band width options are 1·65,2·0,2·5,3·0 or 3·75 metres, and band length 9 to 45 or more metres. An oven with a wire-band conveyor 23 metres long, and 2·5 metres wide, loading pan-straps 570 mm x 240 mm end-on with 4 x 800 g dough-pieces per strap, would provide an output capacity of 3228 units using a 30-minute baking-time, and 3725 units using a 26-minute baking-time. Hearth-bread yields are more difficult to predict, owing to the spacing necessary for a crusty bake, but may be only 50% of panned bread in the same oven, baking-time being also longer, e.g. 60 minutes to ensure crust crispness and thickness. In the industrial bakeries of the COMECON countries, the wire-band tunnel-oven is the most Notes and references 793

utilized oven, for basic breads, variety breads, and rolls. In the GDR, these are manufactured by YEB Kyflhiiuserhiitte, Artern, the most widely used models being the BN 50 and BN 72, with baking-surfaces of 50 and 72 m2 respectively. Figs 120 and 121 show the external features of the BN 50, and baking-temperature/band-Iength relationship within the five heat• zones. The BN 50 wire-band tunnel-oven output is 835 to 1050 kg/h of mixed rye/wheat-flour hearth bread, or 665 to 685 kg/h of bread-rolls. Energy requirements are: town-gas 100m3 h- 1 (18 kW); natural-gas 40m3 h -1 (18 kW); and heavy grade fuel oil 32kg h -1 (30kW). Steam consumption is 80-160 kg h - 1, depending on oven size and product baked. Wire-band speed, and hence baking-time of the BN series ovens, is regulated by a three-phase motor with a variable-speed drive over the drive-roller, mounted at the discharge end of the oven. The selected motor-rpm determining the rotation-time of the band, which is read off a tachometer calibration in minutes, e.g. 3000 rpm/17 minutes, 1500 rpmJ35 minutes, etc. The Simplex 2000, is another highly efficient, high-capacity tunnel-oven, manufactured by APY-Baker (formerly Baker Perkins) of Peterborough PE36TA, UK. This oven also incorporates a recirculating heating system, relocating the heat-flux as required, and utilizing forced convection to increase heat-transfer. Automatic heat modulation burner control, preheated combustion-air, and microprocessor temperature control ensure a consistent bake for panned-, and hearth-breads, rolls, cakes, pastries and pies, etc. Available conveyor widths are 2·5 and 3·0 metres, with lengths up to 36 metres, lengths from 30 m requiring two heat circulation systems in the case of the Simplex 2000E oven. The Simplex 2000 version has conveyor widths of 3·25 and 3-85 metres, with the same length options. Average heat-inputs when running is approximately 70% of the maximum heating up demand, which is 20200 kcal m -1 h -1 for the 2·5 m band width, and 24200 kcal m -1 h -1 for the 3·0 m band width (Simplex 2000E). Comparable heating-up demand for the Simplex 2000 model are: 3·25 m band width 44000 kcal m -1 h -1, and 3-85 m band width 52000 kcal m -1 h -1. Total gross heat-input is calculated in each case by multiplying these figures by the relevant oven• conveyor length in metres. Both the Simplex 2000 and the 2000E incorporate the single constant mass recirculating heating system, which matches heat available to the product requirement profile, and high turn-down automatic modulating burners. The main difference in the models described is the lighter weight grid conveyor for fuel economy with panned and sheeted products, in the case of the Simplex 2000; the Simplex 2000E being designed for European product ranges. Baker), production output is controlled by the capacity of its ovens. This is expressed on an hourly basis, and is often referred to as 'throughput'. In the case of tunnel-ovens, it can be calculated in kg/h from: baking-surface length, number of loaves/row, weight of each loaf (kg), loaf-spacing (mm), baking-time (min), taking into account a conversion factor of 60 for minutes to hours and a factor of 1000 for conversion of millimetres to metres. Such calculations for discontinuous batch ovens are more difficult, owing to additional factors, e.g. loading, baking, further heating, product transfer, and unloading. Comparative throughput measurements between a multi-deck gas-fired cycIothermal system, and a double wire-band return-oven (DWRO), with total baking surfaces of 9·6 m and 13-2 m respectively, indicate values of 144 kg/hour, and 220 kg/hour respectively for the baking of 1·5 kg mixed rye/wheat• flour bread. Schwate, w., and Ulrich, U. (1986) In Special Processes in Baking-Process Manual (German), YEB-Fachbuchverlag, Leipzig, GDR. Effective productivity ofvarious ovens can be calculated by dividing throughput (in kg) by the product of the number of operators and hours of work. Thus, any increase in effective oven productivity can be determined, and expressed as a percentage increase compared with that df the operation of another oven system. The choice of the best oven type and capacity is a difficult task for any bakery, since so many important factors have to be taken into account. Since oven capacity determines throughput of baked products, the personnel requirement, 794 Handbook of breadmaking technology

quality ofthe bake, and production costs, an in-depth evaiuation before making a final choice merits the baker's time. Visits to bakeries with comparable outputs and product ranges to that of the prospective buyer will allow the following points to be assessed on the spot: (1) quality of the bake; (2) floor-space demand; (3) mode of operation and degree of maintenance required; (4) operator costs; (5) installation and fuel supply, steam provision, and burner exhaust flues. Once the type of oven has been decided upon, the various models from manufacturers have to be compared for baking effect and reliability, as well as after sales service versus price. For the industrial bakery, the priqrities influencing choice may be quite different. Although the tunnel-oven demands the most floor-space, it is the most straightforward in design, construction and operation, as well as being the most flexible for different pan sizes and hearth products. Oven-chamber temperature control is also made easier and more accurate by dividing into five heat-zones, and the application of a 'feedback' system (servo-system) with computer-controlled thermostats. The lower crown facilitates steaming, and loading and unloading are located at opposite ends of the oven. The single-lap swing-tray oven, such as the Series 440 oven of APV-Baker, Peterborough, UK, has many of the advantages of the tunnel-oven, and for the production of panned products, offers about 50% economy in floor-space compared with the tunnel-oven of the same output capacity. Heat distribution is divided into four zones, and the design allows superior fuel utilization efficiency compared with tunnel ovens. The 440 Series oven, has a gentle steaming gradient, with still air and bottom radiation, for good oven-spring, followed by a mild convection-zone, . then a high convection-zone whereby adjustable jets direct air flow between the pans for rapid baking. Finally, a mild convection-zone provides even browning on the return run of the trays. Automatic loading and discharge mechanisms have been perfected at the one service• end, and integral in-oven lidding systems added. Conveyorized oven systems are normally integrated with a conveyorized final-proofer, the grid pan conveyor carrying the panned dough through the final-proofer and oven without any transfer breaks. Residence-times in the proofer and oven are usually 60 and 20 minutes respectively. Such systems offer design simplicity and uniformity of bake, each product taking the same path through the oven chamber. Heat-zoning with these ovens is non-existent, but facilities for steaming are possible. Since the original design of the conveyor speed was to be uniform throughout, a longer proofer-conveyor was necessary to accommodate the longer proofing time versus baking-time. However, this problem was overcome in later modifications to Lanham's original system by powering the proofer and oven conveyors with independent drives. The Lanham proof-and-bake system, was developed in 1967 by E. Lanham, bread and roll plant installations being utilized worldwide. The Atlanta-based company now operates under the APV-Lanham title, having been acquired by APV-Baker in 1989. The endless chain conveyor conducts products through proofing, baking and cooling. Pan-straps of six abreast are locked in position on the conveyor, passing evenly through proofer and oven to give a consistent bake. Lanham, W. E. (1970) Baker's Digest, 44, 6, p.54. An important feature of the system is the relative ease of maintenance. In the UK alone, there are currently 14 Lanham plants producing various breads and small fermented products for national groups, independent plants, and burger bun specialists. Lanham have a licence agreement with Tweedy of Burnley for all markets outside North America and Japan involving Tweedy in the design and manufacture of components such as conveyors, oven temperature controls, belt-speeds and pan-spacing. The Lanham system has a good growth potential as a roll production plant. Ribbon-burners utilize either gas or fuel oil; in the latter case they are fitted with oil vapourizers or nozzle burners to perform an atomizing function. The oil is vapourized by a heat source, and the vapour mixed with air for combustion in the correct ratio. The nozzle and gun-type burners used in recirculation ovens can be readily adapted for both gas and oil. These burners have a very wide flame adjustment range, and stability on low turn-down. Notes and references 795

Flanagan, P. (1978) Baker's Digest, 52, 2, p.42. Direct firing still remains the simplest and most energy efficient method of oven heating, being about 15-25% more efficient than an indirect method. Craig, S. (1977) Baker's Digest, 51, 5, p. 131. Multiple banks of ribbon-burners within the oven-chamber, positioned laterally to the direction of product movement on the conveyor, both above and below the baking-surface, are capable of providing reasonable top and bottom heat control. However, ovens using them normally employ a clean-burn gas fuel, and although exhaust flues limit the combustion products, and moisture within the oven-chamber by free convection, some form of forced convection improves the performance of these ovens considerably. This phenomenon is explained by the thermodynamics at the surface of the dough-piece, which are such that heat flux and penetration can be greatly increased by rapid removal of steam emerging at its surface by air turbulence. lndirect-firing-and-heating systems offer the options of gas, fuel oil and other fuels, with no combustion-products entering the oven-chamber, and each burner-chamber forming an oven zone, thus facilitating temperature control, especially with the aid of fans, ducts, and temperature controllers. Indirectly fired ovens, owing to design constraints for the installation of radiant panels, are less efficient in energy utilization than directly fired ovens. Current research into improved heat-transfer is being directed towards the use of combined techniques, making use of VHF energy sources of about 17 MHz, and high-temperature conventional modes of heating. These techniques demand very careful control of the mixed heating modes to keep baking-loss within conventional, acceptable commercial limits. The two-phase process (HF and high temperature) takes about 10 minutes, compared with 30 minutes for conventional baking. The HF mode is applied for about 6 minutes, followed by supplementary high temperature conventional heating for 4-5 minutes at 350°C for crust formation. The HF mode provides a rapid bake-out, and a rapid transition of sensitive enzyme-activity temperature optima, in particular that of alpha-amylase. This permits the use of flours with relatively high alpha-amylase activities (Falling number values for wheat-flour below 200), the lower limit of Falling number values for wheat-flours being about 70, even with two-phase baking. Salovarra, H., et al. (1988) Acta Alimentaria, 17, 1, p. 67-76 (English). The air radio frequency assisted (ARFA) oven system, manufactured by Greenbank-Darwen Engineering, part of the Greenbank Engineering Group, of Blackburn BB 1 3AJ, UK, uses a combination of radio frequency (RF), and forced convection of hot air. Applied simultaneously in the ARF A oven, the baking-time becomes dramatically reduced. The RF element of the process generates heat uniformly within the product, reducing the limiting factors of heat and mass transfer, thus allowing free migration of moisture to the product surface. The air system is then used to remove surface moisture from the product, and impart texture, colour, and develop flavour. This balance being the most efficient use of energy. Metallic conveyors, baking-pans and foil containers can now be tolerated in the RF field, the forced convection nozzles or perforated plates being utilized as the electrodes. The forced convection hot air system is applied from above and below the product, either through an air nozzle system, or through perforated plates. The latter gives lower density RF waves, which can be an advantage for some products. The conveyor material can be: steel-mesh, steel-slats, or non-metallic. The choice of energy source for the hot air system is open, heating being either direct or indirect.

CHAPTER 3.4 CONTROL TECHNOLOGY AND ENERGY RECOVERY

Heat-energy requirements per unit weight of dough per bake show wide variations, depending on dough formulation, structure, mode of baking, and oven-design. Anderson found that by increasing final-proof temperature, and reducing the baking temperature, thus reducing 796 Handbook of breadmaking technology moisture loss, the energy requirement could be reduced from 256·6 per pound of bread to 162·2 per pound (Btu), under control. Anderson, R. C. (1966) Baker's Digest, 40, 6, p.60. Johnson and Hoover, analysed total energy requirements for baking, estimating the following Btu data per pound of bread: oven start-up 77·4; heating during baking 77·0; moisture evaporation 179·7; starch gelatinization 2·0; heating of pan 34·8; insulation loss 45·4; and flue-gas losses 122·4. These results are based on industrial data from a daily production of 80000 Ib of bread, the total energy input per pound of bread being 528·9 Btu. Thus, the two main loss sources in the overall balance are: moisture-evaporation 34·3%, and flue-gas losses 23·2%, together making up more than 50% of Btu consumption. Johnson, L. A., and Hoover, W. J. (1977) Baker's Digest, 51, 5, p.58. Later research by Anderson and Skarin, using an efficient direct-fired oven with gas, good insulation and forced-convection, indicated heat-inputs of 300 to 400 Btuflb of bread as adequate. However, it must be borne in mind that an indirect-fired oven would demand an average of 20% more fuel to compensate for the lower fuel utilization efficiency. Therefore, using 400 Btu/lb bread as a base, and assuming a gas fuel efficiency of 85%, the actual heat• input in net terms entering the oven-chamber would be 340 Btuflb. Of this amount, 250 Btu/lb is necessary to bake the dough, 40 Btu to heat the pan, and the residual 50 Btu being lost as exhaust-gases and through the oven walls. Anderson, R. C. (1973) Bakers Digest, 47, 4, p.40. Skarin, R. (1964) Proc. Am. Soc. Bakery Engineers, 1964, p.88. Burner control systems for direct-fired gas ovens are usually achieved by the fitting of so• called 'ribbon' burners equipped with a flame-band distributor, as shown in Fig. 122. These are installed within the oven-chamber, and generate a strip of flame continuously along their entire length, which can be adjusted laterally by using a lateral heat equalizer. The latter equipment is capable oflateral flame adjustment at any desired level across the oven width. The illustrations show various lateral flame patterns produced by the burners, fitted with a flame band distributor. Indirect-fired ovens, using recirculating (cyclothermal) heating systems, are fitted with larger higher capacity burners, installed singly or in pairs. These generate the hot gases of combustion within their own separate combustion chambers or boxes. Correct gas:air ratios must be maintained to produce the hottest possible flame, burning with a blue colour, with no carbon deposition. The older aspiration burner systems involved conveying the gas to the burner under a pressure of I to 5 psi, the burner design being such that the gas flow produces a venturi-effect, drawing in sufficient air to form a combustible mixture. Manual control was then maintained on each gas control valve. Owing to the quantity of air drawn through depending on the gas flow rate, at low settings insufficient air is drawn in, and efficiency diminishes. Also, the aspirator system is potentially hazardous, should the flame blowout. The ::onal premixer unit avoids these problems by mixing air and gas before being fed through a common header to a number of ribbon-burners, which may be 15 or more. Flynn, J. H., and Flynn, E. S. (1965) Baker's Digest, 39, 3, p.63. Filtered air at 1 psi, is fed into the mixer unit by blowers, and mixes with gas, which has been reduced to zero pressure by a gas pressure regulator, shown in Fig. 123-1, before being fed to the mixer unit. The air:gas mixture is controlled by an air-control valve, which effectively takes over control of the burners. Actuation of this valve is by the temperature controller, which, on sensing a fall in oven temperature, signals the valve motor to increase the air flow into the mixture chamber. More gas is then drawn in, resulting in a flame-size increase to supplement the heat supply. When the oven temperature exceeds the preset temperature level, the air flow rate is reduced, together with the flow of gas, thus reducing the heat supply. These mixer units, which are self-actuated gas/air mixture regulators, are also provided with safety switches, which automatically release hazardous pressure levels, lock-out valves for gas supply, and Notes and references 797

intermittent or continuous spark-ignition. Fig. 123-11 shows the design features of a self• actuated gas/air mixture regulator. Higher levels of control can be obtained by using separate proportional mixer units for each burner fitted, also with low-pressure air and zero-pressure gas lines. Burner control systems generally can be classified into three types according to their degree of sophistication, as follows: (1) a simple on/off mode, the burners being either fully on or off; (2) high/medium/low mode systems, the air/gas controls varying between high and low flame settings, according to heat demand; (3) a modulating, proportional control, valve, which supplies the correct amount of air and gas mixture to the burners, being linked to a temperature controller, which senses temperature in the zone of burner operation, and signals when more or less heat is required. A typical example of a modulation control hook-up, actuating an electric modulating motor on the combustion air-line is illustrated schematically in Fig. 95. This controller has a mercury thermal sensing element installed in the oven• chamber, causing an indicator on the instrument to move up and down the scale in response to the expansion and contraction of the mercury. In turn this moves a contact along a potentiometer coil within the modulating temperature range. The potentiometer coil follows a red-pointer, which can be set at the control point by turning a setter-knob located on the instrument cover. The potentiometer-coil forms one half of a Wheatstone-bridge circuit, and the other half of the bridge is formed by a potentiometer of similar electrical characteristics, built into the proportioning motor and driven by the motor-shaft. The proportioning motor also has an inbuilt detector, detecting any imbalance in the Wheatstone-bridge due to a change in control temperature. This imbalance is then rectified in the form of a balanced bridge circuit by the proportioning motor being driven in an appropriate direction. The motor-shaft is connected via a linkage to a device controlling the amount of air entering the gas-mixture valve. This type of control hook-up between oven temperature and burner, provides accuracies of less than 1·0% of the full scale reading, which is sufficient to maintain oven zone temperatures to within a few degrees of target settings on the instrument. Safety devices are also fitted to modern ovens to prevent hazardous conditions in the event of burner malfunction. Gas or fuel oil ignition may fail owing to an extinguished pilot-light; blockages can occur in fuel lines; a flame may become extinguished by a sudden draught. Unless ovens are equipped with suitable detection and alarm systems, flame failures can result in product under-baking. However, the most fundamentally important safety measure is to have automatic shut-down of the fuel supply to the burner in the event of flame failure (see Fig. 123-II1). Diagnostic-check display instruments are now provided on many multi-deck ovens, whereby, in the event of a fault, the type of breakdown is indicated by lights and symbols, i.e. whether the fault is in the electrical system or the burner system. Thus, faults can be diagnosed by the baker, before contacting the service-engineer. Exhaust-gas (soot) monitors reduce oil consumption and maintenance costs by monitoring the exhaust-gases from combustion, keeping the gap between excess air and the soot limit to a minimum. Oil-consumption monitors lI'ith inbuilt computer update the baker on burner operating time, the number of times the burner is switched on, current oil consumption, amount of oil used since the last reset, and current oil supply versus minimum tank level. Changes in oil flow are immediately apparent for perusal, thus ensuring constant heating-up times, and stable baking conditions. Automated steaming control reduces energy demands when baking products such as bread• rolls in rapid succession. Average losses of steam for rolls are 33%, and about 22% for I-kg hearth long-loaves. These losses can be reduced by up to 10% using an automatic steam system. 798 Handbook of breadmaking technology

Oven control technology must be simple, centralized and well organized for operation, provide an optimal control over the baking-process, simplify repairs and servicing, increase the degree of automation, consist of positive and reliable circuitry, and result in reduced energy consumption. Oven measurement and control systems are divided into two areas: (1) equipment elements, i.e. recording instrumentation, fuel-supply, drive-motors for the conveyor band and speed controls, coupled with the tachometer, and power supply for the bread-cooling plant; (2) control panel, which centrally controls the actual baking-process. As in other branches of industry, microelectronics and information technology are emerging in the baking industry as key technologies. Computerized baking and computer-guided production, applied also in craft-bakeries, reduces stress-induced operational errors and quality fluctuations. In this respect, the two basic possibilities are: control by information• storage programming, which allows the use of the same basic construction unit for various control functions, merely changing the programs of their algorithms; or programming by wire, which involves working out a fixed program, by linking up specific groups of components. Since oven control involves the use of a fixed functional sequence, programming by wire is the obvious choice. Control ofthe correct function of the heating-system is achieved by pipeline pressure manometers, and an air-speed sensor controls the heating-gas circulation. The combustion chamber is protected by an excess temperature sensor; temperature sensors are also placed within the combustion chamber and exhaust-gas vent. Equipment elements tend to be constructed as complete units, e.g. a complete gas burner includes power units for gas and air regulation, ignition and flame control units, and combustion air pressure monitor. Gas feed pipes, magnetic-valves, and gas-pressure• regulator are also built as a complete unit. Temperature sensors and illumination circuits for the various heat-zones are also grouped in one unit. Since the grouping of all these 'block• units' are mechanically and electrically complementary, they can be assembled ready-wired at the point of installation, being connected by clips attached to strips.

Actual control and regulation of the baking process is performed centrally from the control• panel, which is also built up from grouped electrical components. Measurement and read-out aggregates record the temperature in the individual heat-zones of the oven-chamber, and exhaust-gas temperature. Initial temperature of the heating-gas in individual combustion• chambers are regulated by a control-aggregate, which incorporates a tachometer, recording the baking-time relative to the velocity ofthe band-conveyor. Automatic control of the whole baking cycle proceeds from the control panel, but certain control functions can be made independent of the automatic control sequence. In spite of the number of hook-ups and servo (feedback)-systems using microelectronics, the result is more exact than a traditional relay control system can offer. Also, contact-free signal processing is more reliable, and wear-and• tear is almost eliminated. Savings in electro-energy, compared with non-electronic-controlled ovens are of the order of 20%, and savings achieved by the use of 'block' gas burner units range from 16% to 24% of gas consumption. Actual economies depend on the type of product, spacing on the band, and other factors.

Measurement and control equipment generally performs a comparison of specific unknown physical parameters with defined internationally calibrated norms. When associated with a control-system (servo- or feedback), and the measured value deviates from the target value, a related signal is passed to an appropriate control unit. The processing of this signal usually involves a conversion into either electrical or pneumatic units of measurement. Control instrumentation is not provided to measure isolated values, but rather to determine whether measured values lie within a specified tolerance range. Control equipment frees personnel from routine control work, and contributes to safe, hazard-free working by linking to visual and acoustic alarm systems. Figs 123-1 and 123-II, show the principle and components of a gas-pressure regulator, and self-actuated gas/air mixture regulator for the gas-fired cyclothermal wire-band tunnel-oven Type BN 50, manufactured by Kyffhiiuserhiitte, Artern, VEB, in the GDR. Fig. 122 shows the lateral flame patterns developed by ribbon-burners Notes and references 799

fitted with a variable flame-band distributor, which are applied to direct gas-fired ovens with free convection heat distribution. Temperature control systems for ovens, consist of a thermocouple (nickel/chromium/nickel) as the temperature sensing device wired to a calibrated instrument on the control-panel. When a maximum of 650°C is reached, the magnetic-valve on the high-pressure forced-air line falls, thus sealing the air-line. However, a spring-loaded adjusting screw allows enough air to maintain combustion on a low flame on the forced-air line. Thus, the heating-gas temperature in the oven-chamber falls until the thermocouple on the two-point regulator of the control unit for the minimum tolerance limit gives its signal. At this moment, the magnetic-valve opens again, allowing air to pass freely through the forced-air line. In this way, temperature control is achieved via the connecting pipeline to the air pressure within the gas/air mixture regulator, which controls the gas volume feed to the burner. Although any number of thermocouples can be connected to the same instrument, for heat-zone temperature measurement, one instrument for each zone is desirable, the temperature record during the whole baking-cycle being maintained on a chart. The most accurate temperature control for multi-zone ovens is obtained with electronic potentiometers, obtainable in several forms and with special features. Temperature controllers associated with burner control systems are either of the electrical contact or pneumatic, narrow-band throttler type, depending on the type of burner used. The control mode can be on/off, high/low, or modulating. The latter system involves the burner control valve operating in rapid response to preset temperature limits, eliminating large temperature fluctuations. Oven band-conveyor speeds are measured and controlled by electric tachometers (rpm• counters), which can be either direct-current or alternating-current generators, being connected to the band-conveyor drive-shaft. Their output is either measured with a potentiometer or a voltmeter, and is calibrated in terms of baking-time in minutes. The selected three-phase motor-rpm driving the band determines the baking-time of the products. Any band-slip over the drive-drum is detected by the resultant change in band-rpm by the tachometer, and an appropriate alarm signal given. Since baking-time depends on band-rpm, the detection of band-slip is important. Flame ignition and the detection offlame-failure are part of the combustion safety precautions built into all modern ovens. The lighting of ovens follows a programmed sequence to ensure that all elements of the ignition system are functioning properly. Instruments used for the detection of flame failures include flame rods, infrared and ultraviolet detectors, flame electrodes and photoelectric cells. These instruments are all linked to various devices which will cut off the fuel supply. A fuel supply shut-down may be triggered off by variations in the gas or fuel oil pressure, ignition failure, overheating in the combustion-chamber or flue, or an electrical power failure. The most widely used instruments are the flame-electrode and the photoelectric cell. The positioning of these instruments within the heat-development systems of a gas-fired oven, is at (13) in Fig. 123-III, and at (7) in the case of an oil-fired oven respectively, as shown in Fig. 123-III(b). The principle of the flame electrode depends on the fact that a flame, due to ionization, acts as an electrical conductor, forming a circuit. As long as the flame burns, a relay holds the burner feed-valve in the open position, reverting to the closed position and shutting off the fuel supply when a fuel or power interruption occurs. The photoelectric cell, and light sensitive sensors, depend on the closure of a relay as long as a light-emitting flame prevails. If the flame is extinguished, the relay opens, and actuates the relative safety devices, similar to the flame electrode. Re-ignition systems are fitted when the shut-off valve also functions as the temperature control system. Rack-oven automatic and computer-control systems have become important with the rapid growth of rack-ovens for in-stores, freeze~thaw~proof~bake and 'bake-off' operations generally. Their control systems are often integrated into the entire freeze~thaw~proof~bake cycle system. The aim of computerized control is to automatically set-up the optimum 800 Handbook of breadmaking technology

conditions for baking each product group. Typical process variables are air-flow and restart time after loading, some products benefiting from a delay in air-flow restart time. The facility to vary oven temperature profiles during the baking-cycle, steaming levels and steam release are also desirable for some products. When equipped with heat exchangers of adequate dimensions, rack ovens can maintain low exhaust-gas temperatures, thus making efficient use of energy-imput. Exhaust-gas residual heat can also be utilized to preheat the combustion air, in the same manner as applied to tunnel-ovens in industrial bakeries, and multi-deck batch• ovens. The Rototherm RE, manufactured by Werner & Pfleiderer, D-7000 Stuttgart 30, FRG, incorporates the rotating-rack design, and the advantages of the block-building principle. Burner, fan and heat-exchanger form one circuit, independent of the baking-chamber. The block-building unit design technique enables the electrics to be supplied ready for plug-in, the installation electrician only having to make the mains connections via cable to the control• panel. Burner, fan and heat-exchanger can be heated up during the steam exposure-time, thus reducing the temperature-drop normally encountered when loading the oven. Thus making continuous batch-baking possible afterwards. The heat exchanger, burner and steaming device are designed for continuous baking. The Rototherm rack oven is fitted with an automatic baking control system as standard, but the computer control system can be programmed and left to complete all the baking operations in sequence. Once the loaded racks have been wheeled into the oven-chamber, and the door closed, the baking cycle starts by selecting the programme, and pushing the programme start button. After the preset steam exposure-time has elapsed, the air circulation fan starts, and the baking-cycle proceeds until complete, which is signalled acoustically by a bell or gong. The Rototherm is one of the most compact rack-ovens with the rotating turntable, providing a baking-surface per 21 trays of 6·6 to 12·6 m2, depending on the dimensions of the oven-chamber chosen. Power-ratings of these ovens range from 60 to 105 kW/hour for gas and oil-fuel heating, and 42 to 60 kW/hour for electricity. Energy recovery systems have attracted much research in recent years, most of this having been applied to industrial tunnel-ovens. However, with planning and discipline, considerable savings can be made in the economic usage of energy with batch-ovens in the smaller and medium sized bakery. Some elementary considerations are the following: -planning of production schedules to make full use offalling temperatures for a diverse product range, -switching off unwanted multi-deck oven decks when no longer needed, -making full use of off-peak tariffs by staged switch-on of electricity, making full use of electronically based systems, negotiating special terms for bake-schedule versus time, -always aim for maximum oven-loading, especially where pan-straps are utilized for bread, strapping being appropriate to oven dimensions, -making full use of timers for baking to avoid opening oven doors, ensuring steam dampers are closed after steam release, thus avoiding reheating, e.g. rack-ovens, --ensuring regular maintenance of burners to give efficient combustion, correct fuel/air mixture, and flame profiles, thus minimizing carbon deposition, --evaluate current replacement cost against energy losses incurred with existing oven equipment. Since all gas and fuel oil ovens have an exhaust-gas flue-stack for removal oftoxic gaseous by• products of combustion, a large volume of hot gases escape. However, by passing these gases through an efficiently designed and adequately dimensioned heat-exchanger, the exhaust-gas temperature can be reduced to a minimum, and the heat so extracted used for generating both hot air and hot water. Thus, extra heat can be utilized for heating water, proofing-cabinets, or the bakery. In large industrial bakeries, where tunnel-ovens are standard, up to 70% of heat can be recovered from the flue-gases, which can reduce heat-input to the oven by 5-6%. The first step is to evaluate the potential amount of heat available for recovery, appropriate exhaust-gas parameters for measurement are: temperature, volume flow rate/hour, and Notes and references 801

weight/hour. If these figures indicate that a large amount of heat is available for recovery, the installation of a heat exchanger of appropriate dimensions is justified. Heat recovery equipment includes: burner combustion air preheaters; preheaters for boiler water for steam, water-heating; space-heating; heat and steam for proofers. Other sources of waste-heat, at lower temperature and high volume, e.g. steam liberated from ovens, and steam-extraction ducts, are more difficult and expensive in equipment. Advice and information concerning energy conservation schemes can be obtained from government energy departments, and the large oven-construction companies. Heat-exchangers can generate both hot air and hot water, and all oven types from multi-deck to tunnel-ovens can be equipped with these energy saving devices. The usefulness of such systems is described in detail in the study: 'Opportunities for improving energy utilization in bakery ovens' carried out by the Fraunhofer Institute, Miinchen, FRG. The Winkler Bakery Oven and Machil1ery manufacturer, D-7730 VS• Villingen, Black Forest, FRG, have applied these studies in the construction of their Columbus multi-deck ovens. These ovens, having received a design award and approval of merit in 1985 by the Baden-Wiirttemburg State Office of Trade, are compatible with computer-aided production in craft bakeries. Combustion-process efficiency of boilers, baking-ovens, etc. should be maximized by regular measurement of the four flue-gas parameters: oxygen, carbon monoxide, total combustibles and temperature. Portable gas analysers, such as the Teledyne MAX, manufactured by Teledyne Analytical Instruments, Southall, Middlesex, UK, also automatically calculate combustion efficiency in net terms. A theoretical calculation of carbon dioxide content being also provided. When connected to a printer, permanent data can be stored. For in situ exhaust or flue gas analysis, the modular designed WGD in situ analyser, manufactured by Thermox, and marketed by Fluid Data, Crayford, Kent, UK, is a state-of-the-art, compact unit. Energy-loss through insulation defects can be detected with the Emmaflex C-700C non• contact instrument, which measures both temperature, and heat flow (energy loss or gain). Insulation voids can be detected during preventative maintenance of all heating equipment. These instruments, with various measurement ranges, are manufactured by Emmaflex, Milford, Stafford, UK. Non-contact temperature measurement, of inaccessible surfaces, and scanning for surface location of hot-spots, can be performed with the Redpoint THI-300 infrared thermometer. Accuracy is ± 1%, with a 2-s response. Read-out functions are maximum/minimum and average, incorporating a dual Fahrenheit/Centigrade display. Read-out is digital, and the sensor probe is separate from the read-out unit. Dew-point/relative humidity measurement can be carried out with the full-blown, chilled mirror dew-point meter DP 383 R, marketed by Protimeter pic, Marlow, Bucks SL 7 1LX, UK. This is a solid-state instrument of robust design, with digital read-out of dew-point, temperature (ambient), and percentage relative humidity. The sensor probe and read-out units are separate, and it can be used for environmental control and monitoring in ovens and proofers, also water-activity in food, and monitoring storage, and production areas. Lee• Integer Ltd, of Kettering, Northants Nl8 7QW, UK, market a Dewpoint Signal Converter DP800, a block-format electronic module for surface or rail mounting, which converts %RH and temperature signals into a 4-20 mA output dew-point temperature signal, thus providing an alternative method of measuring dew-point, without the need for chilled-mirror techniques. Dew-point temperatures can be measured in a wide range of industrial environments, using rugged probes. These probes incorporate thin film chromium-mosaic capacitive sensors, which is the most advanced relative-humidity sensor currently available. Computer monitoring of energy consumption per process unit or plant allows energy to be treated as any other raw material. By monitoring electricity, gas, oil, and water accurately 802 Handbook of breadmaking technology

throughput the production process, a more precise production cost calculation system can be established, both per process unit, and in total for a production line. Computer software for this task is marketed by Stark Associates, Salfords, Surrey, UK, for use with the IBM-PC. VDU plots of unit consumption per hour for electricity (in kWh), gas (in m3), and water (in Qq, are displayed for daily comparison. Stored information on the hard-disk can be retrieved in time order, as required. Mechanized control ofoven loading, and unloading and depanning is rapidly replacing the rather slow and laborious task of manual loading and unloading. In the case of batch-ovens, devices known as 'setters' are employed for the loading of hearth-baked products. These consist of webbed band-conveyors, which are pushed into the oven-chamber with the products deposited on them. The setter band rollers are then slowly rotated in a counter-clockwise direction, and the band withdrawn from the chamber. This deposits the dough-pieces onto the oven sole at the required spacing. This set-up is only appropriate for use with static sole batch-ovens. In the case of the double wire-band return-oven (DWRO), the loading device can deposit the dough-pieces onto the moving band-conveyors allowing appropriate spacing (see Fig. 126). Pan-strap loading involves the application of a different technique. On emerging from the proofer, the straps are moved by a cross-conveyor into position at the oven-loading platform. When sufficient straps have assembled to fill the oven width, or swing-tray width in the case of the swing-tray oven, a pusher bar, synchronized with the speed of the oven, transfers the pan• straps onto the band-conveyor or the tray in the loading position. Bridge-bands form part of the oven-loading equipment in countries where hearth bread predominates production. These are driven independently by a motor of about 0·8 kW and 125 rpm, over a cable and pulley drive system. On leaving the proofer, and being deposited on the bridge-band, each dough-piece is cut in two places laterally at its extremities by a special cutting-aggregate, made up of 10 circular cutting-wheels mounted on a bar, which is the full width of the band. The height of this bar is adjusted to give the desired depth of cut, as the dough-pieces pass beneath it. These bars are often interchangeable, to allow the use of another bar of band width, which imparts a special embossed pattern on the dough-pieces. The design and working principle of this bridge-band conveyor aggregate is shown in Fig. 124. Depanning, which is hot hazardous work when performed manually, was initially replaced by mechanical depanners, but these aggregates had only limited success. The problem was overcome by vacuum de panning. This technique involves the application of a vacuum to lift the baked loaves from the pans, thus causing minimum damage to both product and pans. Designs vary, but a basic design incorporating a magnetic delidder is illustrated schematically in Fig. 125. Depanning/packaging, can be combined in one unit for rolls and buns. One side of the unit accepting the cupped-pans holding the rolls, suction cups on a vacuum mechanism being aligned to coincide with those of the pan. On the other side, the cartons or trays are placed to receive the rolls. The vacuum head sucks the rolls from the pan in any desired block number from 9 to 20, lifts, then moves over the empty carton, depositing the rolls into it. The empty pans and filled cartons being removed by the conveyor, then another roll-filled pan and empty carton is conveyed in position for the next automatic transfer. Robotic loading of trays and transport containers involves the application of similar concepts. Vacuum-actuated heads moving bagged loaves or packs from dispatch lines into number blocks laterally, then depositing them into the transport containers in a predetermined pattern. Such an operation is fully automated, appropriate menu patterns being programmed into a system according to container dimensions. Automated oven-sole setters transfer hearth products, baking-sheets, and pan-straps of specific dimensions to the oven sole of multi-deck batch-ovens. Notes and references 803

Microprocessor-based oven-controllers, with VDU and keyboard/operator interface can be fed with oven-baking programme-menus for rapid and accurate adjustment of oven• temperature profiles to suit different products.

CHAPTER 3.5 BREAD COOLING AND SETTING

Maturation offermented baked products, involves the processes of cooling and setting, which can take place on racks in the dispatch area, with air turbulence, or within purpose-built continuous coolers. For cooling in the dispatch area, adequate fresh air is essential, which should be filtered from dust particles before it enters the cooling area. The loaves should be allowed to cool down gradually to about 35°C, with adequate spacing, on wire-racks. I-kg loaves should not be transported until they have cooled to this temperature, assuming they are not for slicing, and packaging. Microbial infections during cooling result from contaminated air during cooling, and the presence of excess humidity resulting in condensation. All storage and dispatch areas must be kept clean, well-aerated and free from any contaminating foreign smells. Other aids to general hygiene in bread cooling areas are: the presence of UV-based radiation; 'Insect-o-cutor' discharge units for insect control (lnsect-o-cutor Inc., Georgia 30083, USA), and climatic control (temperature/humidity), combined with ozonization. Bread-rolls should reach the customer within about 8 hours of baking, and should be stored at about 22°C and 70% RH, away from strong sunlight. Loaves ofbread must not be reduced in temperature too quickly, since internal condensation of water vapour in localized zones can cause shrinkage and loss of quality. Industrial bakeries utilize a process of controlled cooling, ensuring optimal product maturation. For panned• bread optimal conditions are a temperature within the range 20 to 24°C, a relative humidity of around 85%, and an air speed adjusted to produce a temperature rise above ambient at the exhaust point of about 100 e. These conditions will allow a 500-g loaf to cool to 40°C within the crumb during a residence-time in the cooler unit of about 1 hour. Continuous conveyor or belt coolers consist of endless multi-tier overhead conveyors, travelling in straight stretches and U-turns at the end of each stretch. Cooling cycles are on average 60 to 90 minutes, the number of cycles applied depending on the type of product. Formulation and product density will determine this factor. The construction of these coolers are sometimes open all round, with an overhead fan to extract the heat radiated, and others are enclosed with panels, forming a tunnel, a counter-current turbulence being used to accelerate the process. The travelling conveyor consists of either a wire-grid or metal-rod capable offlexing during travel. Spiral designs with a single or double helices are also possible, in the latter case the outer helix forms the ascending path, and the inner one the descending product path. These tower-in-tower designs, save floor-space, and provide greater flexibility in conveyor-belt length to accommodate diverse cooling-times for products. An example of this type of system, applied in the GDR is the Universal Transport System 'Regotrans', which can be either floor- or ceiling-mounted. In the GDR, in order to satisfy bread slicing temperatures of about 40°C, the following cooling/maturing times are necessary: rye, rye/wheat, and wheat/rye breads, 3 hours; wheat bread, and toast bread, 2 hours. Schneeweiss, R., and Klose, O. (1981) In Industrial Baking Technology, VEB-Fachbuchverlag, Leipzig, GDR (German). In the UK, average cooling time within the cooler is about 3 hours, the cooler temperature being kept at 20°C, and the RH above that of the surrounding atmosphere. Heat loss of a loaf of bread on leaving the oven is rapid and uniform, independent of atmospheric conditions. Almost the entire heat loss due to radiation is complete within 40 minutes, the loaf surface having cooled to ambient temperature. However, crumb cooling is far from complete. 804 Handbook of breadmaking technology

Initial moisture evaporation loss accounts for only about 50% of the total moisture loss during cooling. Unbound moisture within the crumb migrates slowly towards the crust, and must be allowed to escape to avoid condensation and possible spoilage. The residual 50% will take about 2-3 hours to evaporate under normal circumstances, i.e. no change in external environment. Other types of bread coolers include, tray coolers, rack coolers, and vacuum coolers. Vacuum coolers are a relatively recent innovation, involving the use of a modulated vacuum system, giving a rapid reduction in the product temperature. The cooler consists of a conveyor, which runs through a vacuum chamber tunnel fitted with vertically operating doors at both ends, forming an air-tight seal when closed. Vacuum pumps remove the gases and water vapour from the tunnel, creating a vacuum. Gases become entrapped in the steam, which is also injected into the tunnel. A water-jacketed condenser, condenses the water off. Moisture removal is rapid, due to the partial vacuum within the tunnel, and product temperature decreases. Bread rolls can be reduced from 70°C to 40°C within about 1 minute. Owing to the higher moisture loss, compared with atmospheric cooling, baking times should be reduced by 15-20% to synchronize the final crumb moisture as desired in the final bread, thus ensuring an adequate shelf-life. Moisture content of a loaf of bread on leaving the oven reaches almost zero in the crust when the crust/crumb interface reaches about 100°C; but although the crumb temperature reaches 98 to 100°C, its moisture content exceeds the initial dough moisture by about 12%. On placement in a cooler at 18 to 24°C, with forced convection, the loaf cools rapidly, losing weight in the form of moisture. During cooling there is an initial temperature gradient between crust and crumb of about 14°C, which progressively reduces to zero as cooling becomes complete. This gradient is created by the relatively high crumb temperature, resulting in moisture movement towards the crust. On reaching the temperature of the cooler• atmosphere, the gradient is reduced to zero. However, thermal/moisture conductivity is not the only factor responsible for moisture-loss acceleration during cooling, it is also temperature-dependent. The higher the product temperature, the more rapid the concentration-dependent moisture diffusion proceeds, especially in bread, where diffusion of moisture is often difficult. Still air surrounding the external surface layer of the loaf impedes free external diffusion of moisture into the atmosphere, depending on its temperature. This phenomenon is overcome by the use of forced-air or turbulence. Moisture diffusion from the hot, cooling loaf, at constant evaporative surface, and external air-speed turbulence, depends on the difference in partial pressure of air which becomes saturated as a result of product temperature, and that prevailing in the air immediately circulating around the product on the other side of the boundary layer. The partial pressure of the steam increasing considerably with a rise in temperature of the product. The effect of turbulence being to progressively reduce the thickness of the boundary-layer of still air. Prolonged storage results in the temperature of the cooling loaf falling slightly below that of the surrounding bread~store or cooler. This occurs, since the moisture evaporation from the loafwill continue after the loaf temperature has assumed the temperature of its surroundings, in spite of the delay in its onset. The necessary heat for the evaporation process stems from the crumb-zone adjacent to the crust, and not from the air separated from the crumb by the crust. The thermal-conductivity of the crust is much less than that of the crumb. Auerman, L. J. (1929) Sowjetskoje mukomolje i chlebopetschenija, 3, 12, p.708 (Russian). The graphical illustrations Figs 127 to 132, concerning 'bread cooling and moisture loss', originate from L. 1. Auerman's reference book, The Technology ofBreadmaking, published in Russian in 1972, then published in German by the VEB-Fachbuchverlag, Leipzig, GDR, in 1977 for the benefit of students and scientists in that country. This reference work, encyclopaedic in its coverage, is to be strongly recommended for all students of baking technology in the English-speaking world, including, as it does much 'in-depth' research data. Data used to produce the graphical interpretation shown in Fig. 128 was obtained by Notes and references 805 Auerman and co-workers at the Moscow Technological Institute for the Food Industry (MTIPP). This illustration shows the moisture loss due to drying out, and temperature changes with storage-time, which take place at the centre of the crumb under production conditions. The data was obtained from 1'5 to 1'9kg rye wholemeal bread baked in pans, being an average of 120 investigations, conducted in five production centres throughout the USSR. The temperature of the bread-stores was 19 to 27°C, and the average crumb-moisture of the bread 53%. Immediately on removal from the oven, the moisture loss or 'drying-out' begins. Simultaneously, a redistribution of moisture within the loaf of bread takes place. At the moment of oven withdrawal, the crust is almost moisture-free, but on rapid cooling, the moisture in the crumb, owing to differences in concentration and temperature between the internal and external layers, migrates into the crust. The cooling, and simultaneous water absorption of the crust to levels of 12% to 14%, will depend on the temperature of the bread• store, the weight ofthe loaf, and the storage conditions, taking place over the first 2 to 4 hours after baking. The crust moisture level of 12-14%, approximates to its equilibrium-relative• humidity (e.r.h.), remaining constant during the remaining storage period. In contrast, the moisture of the bread-crumb continues to fall during storage. Data used for the graphical interpretation shown in Fig. 129, was obtained by the All-Union Institute for Research to the Baking Industry of the USSR (WNIIChP). The moisture-loss of 467 mixed rye/wheat wholemeal flour breads (70% rye:30% wheat) were studied over a period of 5 days by means of changes in their weight taking place on bread-rack trolleys under production conditions. The total surface area of the 467 loaves was46·15 m2, and the absolute initial moisture of the loaves 94·7% (moisture in percentage based on dry matter of the material). On this basis, the drying-out and absolute moisture curves shown in Fig. 129; and the curves for drying-speed, Fig. 132, were obtained. As Fig. 132 shows, during the process of natural moisture loss of the bread, the drying-out rate falls, depending on the cooling process, until a point tk is rapidly reached, then it remains constant. The point tk is easily read off the drying-out rate curve, in this case the W: being equivalent to 85%. Normally this Ik value coincides with the moment in time when the loaf temperature acquires the ambient temperature. Therefore, the time period of moisture loss can be divided into two phases, the first phase being one of a rapidly changing drying-out rate from to to I k , and the second phase one of a constant rate of drying-out, and moisture loss. During the first phase of moisture loss, the rate of drying-out falls with falling bread-temperature, and the temperature-gradient within the bread. During the second phase, the bread-temperature approximates to that of the surrounding atmosphere, remaining practically constant. As a result, the moisture-loss (drying-out) occurs at a constant rate, largely determined by the hydrophilic properties of the bread, its dimensions, shape, and the environmental parameters (temperature, RH, and air speed). Fig. 132 clearly indicates that the rate of moisture loss during the first phase of the cooling/drying-out time period is greatest, and during the second phase is considerably less. It therefore follows that any shortening of the first phase of the total time period is the best method of reducing evaporation losses during cooling. In practice, this is achieved by rapid cooling of the bread on removal from the oven, down to the ambient temperature of bread-stores. Auerman, L. J. (1977) In Technology of Breadmaking, VEB-Fachbuchverlag, Leipzig, GDR (German), paragraph 9'1, p.282--4. Initial changes in bread moisture during the first 30-60 minutes after baking involve a reduction in those crumb-layers adjacent to the crust, owing to migration of moisture into the dried-out crust and subsequent evaporation towards the exterior. This results in the moisture of the outer layers and the inner layers of the crumb reaching the same level of moisture, which is 1·0% to 1·5% less than on withdrawal from the oven. Subsequent cooling and storage results in these crumb-layers near the crust losing moisture much more rapidly than those nearer the loaf centre. Prolonged storage for several days often results in the crumb-layers immediately below the crust becoming quite hard, due to moisture loss. Even light pressure at the surface fails to 806 Handbook of breadmaking technology deform the crust. According to research carried out by the WNIIChP, Moscow, USSR, the moisture level of crumb-layer adjacent to the crust falls within 3 days after baking from 44% (3 hours after leaving the oven) to 18%, and the thickness of this hardened layer amounts to 4-5mm. Auerman, L. J. (1977) In Technology of Breadmaking, VEB-Fachbuchverlag, Leipzig, GDR (German), paragraph 9.1, p.281. Air-temperature of the bread-store influences the rate of cooling, and the moisture loss of the bread. The higher the temperature of the atmosphere surrounding the bread during storage, after removal from the oven, the more intensive the moisture loss. Auerman, L. J. (1932) Snabtechisdat, Moscow. Weight loss of bread during cooling and storage (Russian). Moisture-loss of Ukrainian bread of 1·2 kg during storage for 8 hours at 43-50°C was 5%, compared with only 2% at 11·5 to 19°C. The storage of bread in the frozen state reduces moisture loss to a minimum (see Fig. 133). Relative humidity of the bread-store also influences the rate of moisture loss. Moisture loss is reduced with increasing relative humidity of the bread-store atmosphere. Higher humidities result in smaller differences in partial pressure at the loaf-surface and in the air, thus reducing the rate of moisture loss. However, this effect is not very significant during the first phase of cooling, since the higher bread-temperature increases the partial vapour pressure above the loaf-surface, any difference between this and the partial vapour pressure of the air being too small for significance. During the second phase of moisture loss, when the bread-temperature does not exceed the ambient bread-store temperature, the influence of relative humidity on the intensity of moisture loss increases. Nevertheless, during normal cooling/storage times of 3 to 6 hours under production conditions, the second phase of moisture loss is very short. Forced-air turbulence is also expedient during the first phase of bread cooling and moisture loss. Fig. 134 illustrates the effect of various air-speeds on the moisture loss of bread during cooling. When the bread is surrounded with turbulent forced-air at speeds of O· 3 to 0·5 mis, this shortens the time period for the first cooling phase, simultaneously reducing the weight loss due to evaporation by about 0·5% to 0·7%. Research carried out at the WNIIChP in Moscow, placing bread-rack trolleys within a chamber cooled by an air-conditioning plant, has shown that the cooling process is speeded up, and the moisture loss reduced by 0·5% to 0·9%. Loaf-moisture and baking-loss influence moisture loss due to evaporation. Further research work carried out at the WNIIChP in Moscow, has confirmed that the higher the loaf• moisture, the greater the weight loss under otherwise identical conditions. An increase in the crumb-moisture content of rye bread made from wholemeal flour, of 2%, results in an increase in the moisture loss of the baked bread over 4 hours of 0·26% to 0·42%, and over a period of 7 hours of 0·42% to 0·50%. WNIIChP research also confirmed that there exists a reciprocal relationship between baking-loss and moisture loss due to drying-out as a result of cooling and evaporation. The greater the baking-loss, the lower the drying-out loss, due to cooling and evaporation, and vice versa. Mode of baking (i.e. in pan or on hearth) and loaf-volume also influence bread moisture loss. Hearth-baked breads always show larger baking-losses, and lower crumb-moisture levels than pan-baked breads of the same weight. Therefore, moisture loss due to evaporation in the case of panned bread is generally greater than that of hearth breads. Auerman established that in the case of rye bread made from wholemeal flour weighing 1·1 kg, baked in pans, and as round hearth loaves, significant loss differences occurred. Crumb moistures were 52·8% and 49·2% for panned- and hearth-breads, respectively; baking-losses were 11·6% and 13·3% respectively; and moisture losses after 4 hours storage were 2·03% and 0·86% respectively; after 6 hours, storage moisture losses were 2·19% and 1·04% respectively. Auerman, L. J. (1977) In Technology of Breadmaking, VEB-Fachbuchverlag, Leipzig, GDR, p.286 (German). Notes and references 807

Raw materials and formulation determine final loaf texture and crumb-porosity. Breads of low density and high specific volume will show larger moisture losses, due to baking and cooling, than those made from leaner, denser formulations generally. Dimensional size of the loaf also determines moisture losses, larger units showing lower moisture losses. Bread quality changes due to storage after baking are essential for bread ripening or maturation, and must not be confused with the processes of 'ageing' or 'staling', which set in later, resulting in diminished freshness and palatability. These latter changes commence after about 22 hours in the case of a I-kg wheat-bread, whereas rye-bread can remain palatable for up to 40 to 60 hours without packaging. Bread-rolls reach this stage at about 7 hours after baking. Packaged loaves remain palatable for periods up to 6 days. The maturation processes involve a series of complex physical-chemical reactions, which are interrelated, and include both crust and crumb. Loaves of 1 kg or more take longer to cool, the crumb taking much longer than the crust. After about 1 to 3 hours after removal from the oven, the crumb centre often still has a temperature of 50 to 60°C, therefore many processes taking place during the baking process will continue. Depending on the type of bread, contents of sugars, dextrins, and total water-soluble carbohydrate, amongst other substances, increase during the cooling period. In addition, the gelatinization of starch, and crumb stickiness increase. Such observations were made by Gogoberdise, N. I., Auerman, L. J., and Stscherbatenko, W. W., during the period 1956-58, and reported in publications of both the MTIPP, and WNIIChP in Moscow, USSR. As long as crumb temperatures remain at 60°C or over, increases in crumb sugars, and total water-solubles can occur. During the heat-sterilization of bread to prolong shelf-life, whereby, the centre of crumb can rise to 85°C, sugars and water-solubles increase. Romanov, A. N. (1953) Bread storage. In Pistschepromisdat, Moscow, 1953. Changes in the composition of Wheat bread during storage in polyethylene packaging have been studied by Gasiorowski, H., and Jankowski, S. Gasiorowski, H., and Jankowski, S. (1967) Brot und Gebiick, 21, 7, p. 137 (German). This study comprises storage periods of up to 15 days, at temperatures of - 23 to + 65°C, measuring effects on such bread parameters as: crumb and crust moisture; starch; soluble starch; dextrins with a defined chain-length in the crumb; reducing sugars and total sugars in the crumb; tit ratable acidity; pH; X-ray spectrum; and properties such as colour, compressibility and swelling. Sensory evaluations for freshness, flavour and aroma of the bread were also included. The binding capacity between starch, protein and water playa major part in bread ripening or maturation after baking. After baking, the crumb cell walls are in a swollen state, water being partly physically and partly chemically bound by adsorption. At 70°C, and above, the crumb is in the form of an elastic gel, but on cooling forms a solid mass, during which phase chemical reactions take place. At 60°C and below, intramolecular hydrogen bonding takes place, cumulatively representing high levels of energy. These form within the starch and protein molecules, as well as between the amylose and amylopectin intermolecularly, thus forming the firm crumb structure of the loaf. In this manner, bonding between molecules become progressively closer, and more hydrogen bonds are formed, the energy so liberated giving rise to dehydration. Some of the water released is taken up by the proteins, and the rest is lost by diffusion. Water plays an important part in both maturation and staling, after baking. Loss of heat and moisture during cooling are interrelated, water loss being brought about by the high water vapour partial pressure, which depends on temperature. Maturation also involves the loss of labile highly volatile aroma compounds, which decompose, the more stable aroma compounds diffusing into the crumb on solidification (see Fig. 135). Physically and chemically bound water becomes either lost, or condensed to produce the optimal eating properties. Chemical ripening processes are intermolecular bondings, whereas the physical ones involve mainly moisture loss and the diffusion of highly volatile aroma substances. Physical changes exert an important influence on bread cooling and storage. After baking, loaf crumb temperature at the centre is about 98°C, and at 1 cm below the crust about 110°C. The temperature falls most rapidly at first in this area below the crust, the temperature at the 808 Handbook of breadmaking technology centre of the loaf only falling very slowly. Fig. 136 clearly shows the relative temperature-falls with time taking place at various locations within a 1-kg wheat-bread during storage under specified conditions of 24°C and RH 40%. Rapidity of the cooling process, will depend on ambient storage temperature and RH, and air turbulence, and proceeds until a temperature equilibrium with the surroundings is attained. Owing to an RH gradient between the loaf crumb, at about 100% RH, and the external surrounds at 40% to 60% RH, a process of diffusion takes place, removing about 2263 J/g of heat at boiling point, and atmospheric pressure, resulting in further cooling. An approximate rate of cooling of the loaf can be estimated from the basic Newtonian law of cooling equation, and the total heat lost during cooling from the general heat equation:

Q = loaf-mass x specific heats x temperature drop taking into consideration the specific heat of crumb and crust, and crust-thickness. The total heat loss of a 1-kg white loaf amounts to about 180 kJ. This loss of heat simultaneously results in water vapour condensation within the loaf. A 1-kg wheat loaf of 2000ml, and water content 45%, contains about 0·5% moisture in the vapour form according to Schneeweiss and Klose. Schnee weiss, R., and Klose, O. (1981) In Technology of Industrial Baking, VEB• Fachbuchverlag, Leipzig, GDR, 1981, p.424 (German). Although, during cooling, part of the water vapour is lost, most of it condenses, forming a partial vacuum, causing the air immediately surrounding the loaf to be sucked in. Proof of this fact can be obtained by the tightly sealed packaging of a loaf immediately after baking, th partial vacuum formed leading to a deformation of the loaf. Schneeweiss and Klose studied the volume change of a panned white loaf of 1 kg, which was packaged immediately after removal from the oven, by measuring after various time intervals (see Fig. 138). Volume changes were found to be greatest during the first 15 minutes after baking. After 45 minutes, a physical equilibrium between the partial vacuum and the partial water pressure became established, after which only insignificant volume changes take place. Loaf-volume was measured by placing the hot loaf in a glass desiccator, perfectly sealed. The developed partial vacuum was measured with a V-tube mercury manometer. The largest reduction in pressure was recorded during the first 60 minutes of cooling. In the case of unwrapped bread, this pressure difference due to the sucking-in of the surrounding air became equalized, which was measured with a gasometer, directly (see Fig. 137). These researchers also draw attention to the significance of partial pressure/suction effects for the potential microbial infection of bread by mould. Since the amount of atmospheric medium adsorbed is greatest during the first few minutes after removal from the oven, microbial infection will commence at this stage. However, owing to the initial high temperature of the loaf surface, most of the spores become killed, a greater infection hazard being expected after about 5 minutes exposure to the atmosphere (see Fig. 139). It was found that bread packed about 5-6 hours after baking, owing to its lower crust moisture, showed reduced spore growth, although the actual spore contamination level was the same. When cooling is complete, the partial vacuum becomes equalized, and any spores then settling on the dry top-crust present less danger to the mould• free shelf-life of the bread. This emphasizes the need to cool bread in a storage atmosphere, which is as low as possible in spore content. For each type of baked product there exists a relationship between quality and storage-time, assuming the products are stored at 18-22°C and 70-80% RH. Specific storage-time limits can be placed on products, in order to categorize them as: 'still-fresh'; 'still-edible'; and 'onset-of-staling'. Bread rolls can be described as 'fresh' at up to 4 hours after baking; at up to 6 hours they can be described as 'still-edible'; but at 7 hours or more, there exists the 'onset-of-staling' (see Table 70). Structual solidification of the loaf crumb involves its transition from a structureless gel. This process commences on its removal from the oven, and finishes after 6-8 days, when the loaf becomes hard, dry, and crumbly. Crumb solidification is achieved by molecular bonding at temperatures below 60°C as the loaf cools. Hydrogen bonding plays an important part in this Notes and references 809

process, particularly between the amylose and amylopectin molecules of the starch, forming crumb porosity. Physical covariables which influence this process are: rates of temperature and heat loss, moisture-loss and diffusion, and surrounding air turbulence. The large moisture loss during the first few hours of cooling is due to the large difference in water pressure between the surrounding atmosphere and the loaf. Comparisons between the cooling curve and moisture diffusion, water-vapour partial pressure, and the latter's codependence on temperature (Fig. 137) confirm a close relationship between these physical variables. On reaching the ambient temperature of25-26°C, moisture loss per unit time tends to approach a constant value. Dynamic/mechanical thermal analysis, involving a torsion rheometer system, applied in the testing of polymer-melts in polymer research, can also be applied to dough during the 'heat• up' and 'cool-down' stages of processing. Heat-up and cool-down measurements are performed in the torsion-head, consisting of parallel plates, one being a disk-rotor, driven by a continuous rotating motor at the top; and the bottom plate, the oscillating-plate, driven by an electromechanical oscillating force transducer from the base. Small oscillations of controlled amplitude, using frequency sweeps of 0·02 to 50 Hz, with about four points per decade, can be utilized to obtain viscoelastic data. Measurements at low strain amplitude, under isothermal conditions, with temperature increased, and then decreased in steps, can be applied. A 10minute equilibrium is allowed at isothermal temperature, and the frequency sweep is completed in 20 minutes. Intervals of lOoC during heat-up, and 4°C during cool• down can be taken for isothermal temperature measurements. Relaxation modulus peaks obtained depend on the measurement frequencies used. At high frequencies the peaks indicate polymer chain entanglement, and at low frequencies peaks are interpreted as being due to the association of hydroxyl chain ends by hydrogen bonding. In the preparation of viscoelastic dough, the water content is the most critical factor. The storage (elastic) modulus, designated G'; and the loss (viscous) modulus, designated G", both decrease with increasing dough water content, there being no observed interactions between frequency and water content. This dynamic test method is ideal for monitoring flour-processing properties, and dough-baking physics continuously during the whole baking process. However, since strain sweep tests show a sharp fall in G' at strain rates above 0'2%, baking sweeps have to be carried out at very low strain, so that the dough structure is not disturbed during the experiment. The baking experimental sweep shows an increase and a decrease of both G' and G", as a result of starch gelatinization, and molecular interactions between the flour components and water during the baking process. The maxima or peaks obtained at starch pasting and the final values of G' and G" are highly correlated with flour quality parameters. Therefore, the baking sweep curves are a good procedure for monitoring and interpreting structural/textural changes in dough during processing. The RFS II Fluids Spectrometer, marketed in Europe by Rheometrics Europe GmbH, Hahnstrasse 70, D-6000 Frankfurt 71, FRG, and Rheometrics, Inc., One Possumtown Road, Piscataway, NJ 08854, USA, offers dynamic and steady testing, with independent control of oscillation frequency, strain, and temperature. Frequency and strain sweeps, and a stress relaxation mode are standard options. Menu-driven software, provided with the computer-controlled system, allows temperature-dependent studies to be made, as well as sequenced test routines for quality control testing. Measurements can be made with the RFS II in steady or dynamic shear, using parallel plate, cone and plate, or couette geometries. Properties evaluated include such viscoelastic data as: steady shear viscosity (n), complex viscosity (n'), complex modulus (G), elastic modulus (G'), loss modulus (G"), and damping of low viscosity materials (tan d). Weipert, D. (1987) Getreide Mehl und Brot, 41, 11 (German). Faubion, 1. M. (1985) In Rheology of Wheat Products, AACC, St. Paul, MN, p. 91 (English). Bread staling can be measured by monitoring the crumb response to pressure deformation with time, referred to as 'compressibility'. For this purpose, the Instron test equipment is often applied. Important consumer characteristics are: appearance, smell, taste, and digestibility. Freshness is identified by crispness, a pleasant smell, and an aroma profile consisting of a 810 Handbook of breadmaking technology

complex mixture of volatile and less volatile compounds. Aldehydes, fonning the bulk of the aroma substances, are chemically unstable and readily oxidized to carbonic acid. Their stability depends on the formation of addition compounds with the amylose or amylopectin molecule of the starch. Schoch, T. 1. (1965) Bakers Digest, 39, 2, p.48. Schoch considers that the spiral amylose chain is most likely to assume this role, since on reheating stale bread, aromatic aldehydes become released. Aroma substances initially prolific in the crust of the loaf, migrate into the crumb zone immediately under it during a 20- hour storage period, then towards the crumb centre. However, after 20 hours, the content of aroma substances within the crumb decrease, owing not to evaporation, but to chemical or physical transformation into unknown non-aromatic compounds. Although the crust loses its aroma substances by diffusion, the carbonyl content of the crumb will increase to a maximum up to the second or third day of storage, owing to the condensation of less volatile aldehydes with moisture into the crumb area, under the influence of a partial vacuum. An exchange of aroma substances between crust and crumb is evident after about 24 hours, when furfural becomes detectable in the crumb, whereas, immediately after baking it can only be detected in the crust. This exchange of aroma substances between crumb and crust also takes place in packaged bread; too rapid packaging after baking must be avoided to allow adequate cooling, moisture loss and evaporation of unstable, highly volatile aroma components, which would give rise to undesirable aroma contributions. Within the crumb, many chemical and physical changes take place during cooling, which contribute to an aromatic balanced flavour profile. The crust, however, being of low moisture and crisp, changes relatively little. During prolonged storage, some moisture from the crumb migrates into the crust, resulting in it becoming tough and leathery. This movement of moisture from crumb to crust is the best general indicator of freshness, since it parallels crumb-firming, and loss of sensory attributes. The packaging of bread in moisture-proof material promotes crust-staling, since evaporation is restricted, and the crust retains larger amounts of water. Processes and mechanisms ofthe staling ofbread have been studied for well over 100 years, but their exact nature remain obscure. The idea that bread staling is due to moisture loss was disproved by Boussingault. Boussingault, M. (1853) Ann. Chim. Phys., 38, p.490. Storage under conditions of zero moisture loss, still resulted in staling. Also, the well-known method of reheating bread to recover its freshness confirms this fact, since, in spite of additional moisture loss, the crumb recovers its physical properties of freshness. Increases in crumbliness, and reduction in crumb compressibility, are symptoms of staling, and not its cause. However, there is a limit to refreshing bread by reheating, as confirmed by von Bibra. von Bibra, E. (1861) Getreidearten und das Brot, Nuremburg, FRG (German). von Bibra showed that products whose moisture content were reduced to less than 30%, could no longer be refreshed. Owing to the diversity of the changes taking place, isolation of anyone process for study is very difficult, and few theories have found general acceptance. Microstructural changes in the bread crumb, observed by Auerman, reported in his reference work Technology of Breadmaking form a sound basis for further research. Auerman, L. 1. (1977) In Technology of Breadmaking, VEB-Fachbuchverlag, Leipzig, GDR, p.291 (German). Original Russian edition, 1972, Moscow, USSR(Russian). Auerman states that bread-crumb structure depends on cell wall formation, which, on baking, build crumb porosity in the form of a spongy framework. Microscopic examination of these pore cell walls, reveal a mass of coagulated gluten proteins, with swollen, partially gelatinized starch granules embedded in them. Although these granules expand somewhat, they remain parallel, and surrounded on all sides by coagulated protein, only a few isolated granules being in direct contact with one another. Coagulated protein forms the continuous phase of the spongy crumb framework. In fresh bread, the starch granules lie close to the coagulated protein surface throughout, and no sharply visible boundary layer can be seen between them. In staling bread, the granularity of the partially gelatinized starch is clearly Notes and references 811 visible, owing to the formation of a thin layer of air around part of the granule surface. The older the bread, the more clearly visible the air layers become, thus confirming the volume shrinkage of the starch. Structural changes in the protein of the cell walls were not discernible under the microscope. The build-up of these thin layers of air around these changed granules are considered responsible for the increasing crumbliness of staling bread. It is pointed out, however, that the volume change of the starch granules is not the staling process, but probably its effect. Numerous further tests confirmed that during bread staling, the hydrophilic properties of the crumb change. The swelling capacity and water absorption capacity of the crumb become reduced, together with the solubility of the colloids and other components. Total water solubles are reduced, and the water solubility of the starch. However, it is acknowledged that although changes in hydrophilic properties of the crumb affect its physical properties, these changes represent effects of staling rather than their direct cause.

Retrogradation of starch was first associated with bread staling by Lindet in 1902. Lindet, L. (1902) Bull. Soc. Chern. de Paris, 27, p.634. As the term implies, 'retrogradation' involves a process of reversion, in this case a reversion to the crystalline state, after becoming transformed into the amorphous state as a result of partial gelatinization, and absorption of water from the gluten proteins and other hydrocolloids, during coagulation at baking. On subsequent storage, the starch within the crumb tends to gradually revert to the crystalline form in which it existed within the dough before baking. This process results in the starch structure becoming firmer, less soluble, and part of its absorbed water taken up by the proteins of the crumb. With the aid of the X-ray spectrograph, Katz during 1930-32 was able to gain more fundamental information on starch crystallization, and the effects of temperature and moisture on any changes taking place. Katz, J. R. (1930,1931, 1932)Z.jiir physik. Chern ie, Abt. A, 150, 1, p. 60 and 67; 2, p. 81, 90 and 100; 155, 3/4, p. 199; 158, 5/6, p. 321, 337 and 346. Katz established that the initial native starch of wheat and flour gave an X-ray spectrum typical for a crystalline material, which pattern persisted in the dough up to the baking stage. During baking, limited gelatinization took place, depending on the amount of available water in the dough, but being insufficient for complete gelatinization. The pattern of the X-ray so produced being referred to as a V-pattern, differing from the original native pattern. This characterized the presence of an amorphous element, and a crystalline element within the structure. The crystalline element, however, being quite different from that in the flour and dough before baking. The crumb of stale bread gave an X-ray pattern designated as B• pattern, which was a combination of the initial pure crystalline pattern, and the V-pattern. Moreover, with increasing staling, the B-pattern became increasingly like the pure crystalline pattern in character. This X-ray pattern-B of staled bread Katz designated as the 'starch-retrogradation-spectrum'. Katz regarded the starch in the bread crumb as a thermodynamic system in equilibrium, consisting of alpha- and beta-starch forms. The alpha form being typical for fresh bread, and the beta form for staled bread. The alpha form being stable at temperatures above 60°e. At this temperature, no retrogradation can take place, and the crumb remains in a non-staled state. At temperatures from 60°C down to -lOoC, the system equilibrium shifts in favour of beta-starch, characteristic for staled bread. Katz also emphasized the importance of temperature and moisture for these changes. When loaf moisture fell below 16-4%, or when it was moistened with excess water, the physical effects of staling did not occur. Breads stored under controlled conditions of temperature and moisture from 24 to 48 hours at 60°C or above remained fresh; becoming semi-stale at 40°C; almost stale at 30°C; stale at 17°C; and very stale at O°e. Remaining quite fresh between - 7 and -184°e. These temperature ranges form the basis of recommended storage conditions valid today. Schoch, T. J. (1965) Bakers Digest, 39, 2, p.48. Schoch, T. J., and French, D. (1947) Cereal Chern., 24, p.231. 812 Handbook of breadmaking technology

Schoch and French also considered that the starch granule only underwent partial gelatinization and limited swelling during baking, owing to the limited availability of water in the dough. With increasing swelling, the linear amylose fraction becomes more soluble, and diffuses outwards into the aqueous phase, as illustrated in Fig. 140. Continuous swelling results in increasing concentration of amylose in the interstitial regions, forming a concentrated solution. This concentrated solution setting to a gel by the time the loaf has cooled, Schoch considering that amylose tends to retrograde. Fresh bread is considered to contain swollen, elastic starch granules embedded in a firm amylose gel matrix. This gel remaining stable during further storage, and not participating in the staling processes. Crumb firming is attributed to changes in the physical orientation of the branched amylopectin molecules of starch, within the swollen granule. In fresh bread, according to Schoch, the branched chains of the amylopectin are outspread, within the limits of available water, forming a concentrated system. However, the outer branches of the amylopectin gradually aggregate, aligning with one another by various types of bonding. This system, being less stable than retrogradation, can be regarded as an intramolecular association, which solubilizes again under moderate heating at 60°C plus. In staling bread, at temperatures between 60°C and -lOoC, this system gives rise to increasing rigidity of the structure of the swollen granule internally, thus explaining the effects of crumb hardening. (see Fig. 140). This original concept of Schoch has undergone some enhancement by Lineback in 1984. Lineback, D. R. (1984) The role of Starch in Bread Staling. In International Symposium on Advances in Baking Science and Technology, published by Department of Grain Science, Kansas State University, Manhatten, KS, USA. The intention of this concept enhancement is to explain the mechanical functions of starch. Amylose is also involved in the staling process, although amylopectin plays the most important role. Schneeweiss and Klose have established a decrease in soluble amylose during the staling process, falling from about 8 mg/g starch to about 3 mg/g starch, after 2 days' storage (see Fig. 147). As a result of the retrograding (crystallizing) amylopectin, the retrograding amylose can occupy vacant space within the spatial network structure, which could account for the reduction in soluble amylose during staling. The formation of intermolecular bonds result in structural changes, amongst which, a stretching of the starch helix takes place. This in turn will depend on the conformation of the amylose. The necessary energy required to stretch the helix, and for dehydration, is supplied by the formation of hydrogen bonds according to Hollo. Hollo, J., et al. (1959) Periodica Polytechnica, 3, 3, p.163. The process of amylose retrogradation (English). Hollo considers that the whole process of retrogradation of starch after the hydration during the baking process, can be explained in three stages: -the helical macromolecules become stretched as a result of the absorption of energy, -after loss of the hydration-shell, a reorientation takes place, -hydrogen bonds form between the hydroxyl groups of the amylose, and a crystalline structure emerges. (See Fig. 148.) An intergranular function of both amylopectin and amylose in structural firming is the subject of another postulate, whereby portions of both amylose and amylopectin molecules extend from the swollen starch granules. These then associate with other carbohydrate chains present in the interstitial aqueous phase, and with those extending from granules in close proximity to one another. Crumb-compressibility, or elastic modulus, increases as the storage temperature falls to O°C, and is proportional to the concentration of crystallized starch present during staling, according to Cornford and co-workers. Cornford, S. J., et al. (1964) Cereal Chem., 41, p. 216. Notes and references 813

Data obtained by these workers indicated that the mechanism of starch retrogradation is one of instantaneous nucleation and crystalline growth. Senti, F. R., and Dimler, R. J. (1960) Bakers Digest, 34, 1, p.28. Senti and Dimler also postulate a change of state to explain crumb staling. Starch is at a higher energy level in the amorphous form than in the crystalline form. In the absence of external energy, the gelatinized starch tends to retrograde from the amorphous state to the lower-energy crystalline state. This involves a structural reorientation of the linear molecules into a more orderly structure of lateral bonding between chains. Crystallization can account for about 15% of the starch, forming rigid, insoluble regions. These chains, extending through many intervening amorphous regions, interlink the crystallized regions to form a three-dimensional network, within which, the rigid retrograded areas form a backbone for polymer chain entanglement. Hollo, J., et al. (1960) Starke, 12, p. 106, postulates the three-stage process of retrogradation: (1) Breaking of intramolecular bonds, and uncoiling of the helix. (2) Loss of bound water (hydration-shells), and molecular reorientation. (3) Hydrogen bonding between adjacent chains forming crystalline areas. If heat is applied to the retrograded gel, the hydrogen bonds joining linear molecules in the crystalline areas are broken, allowing free kinetic movement for the chains, permitting reversion to the normal helical conformation. This explains the mechanism of retrogradation reversal when stale bread is reheated, as illustrated in Figs 140 and 141. The most comprehensive staling model has been presented by Knjaginicev in the USSR. Knjaginicev, M. J. (1965) Russ. Journal ofChem. Allunion Mendelejew Institute, Moscow, 10,3, p.227-86 (Russian). The essence of his postulates are that staling is caused by the change in distribution of water, as illustrated in Fig. 144. According to Knjaginicev, bread, depending on the type, begins to lose its original softness at 6-10 hours after baking, when stored at normal temperatures of 15 to 20°C. The crumb becoming friable, and the bread loses its aroma. During the first 3 days, the moisture content of the crumb centre remains constant, but staling proceeds independently, as confirmed by the following researchers. Auerman, L. J. (1956) In Technology of Baking, 6th edn, Piscepromizdat, Moscow. Scerbatenko, V. V., Gogoberdize, N. I., and Zelman, G. S. (1962) In Maintenance of the Freshness of Bread, CINTIPisceprom., Moscow. The crumb perimeter loses moisture, forming a dense layer of 3-5 mm thickness, restricting compressibility when pressed with the fingers, as practised by the consumer. A comparison between the crumb of a staling loaf with that of a fresh one, in spite of equal moisture contents, showed many differences in measurable parameters, as follows: compressibility (elasticity) of the crumb sharply reduced, and the mechanical firmness of the cell walls increased; content of bound-water is reduced; the relative viscosity of an aqueous crumb extract, prepared by rubbing and filtering, together with its relative speed of filtration, both become considerably reduced. Stale bread crumbliness markedly increases, and the water solubility of the crumb components become reduced according to Auerman and Nikolaev and Kulman (Colloids during Baking, Moscow, 1940 and 1956). (See Fig. 142.) Viscosity of the Crumb-suspension, measured with the Amylograph is measurably reduced, with increasing loss of freshness. (See Fig. 143.) Enikeeva, N. G., and Auerman, L. J. (1956) Moscow Tech. Inst. Food Industry, 4, p. 105 (Russian). Bechtel, W. J., Meisner, D. F., and Bradley, W. F. (1954) Cereal Chem., 31, 3, p. 171. Ability of the bread-crumb to bleach methylene blue also decreases with staling. Auerman, L. J., and Rachmankulova, R. G. (1957) Bread and Confectionery Industry, 2, p.22 (Russian). Nazarov, V. I., Sacharov, V. G., and Tichomirova, T. P. (1958) High School News Food Technology, No.4, p. 113. 814 Handbook of breadmaking technology

Resistance of crumb-starch to beta-amylase in stale bread becomes reduced compared with that of fresh bread. Rachmankulova, R. G., and Falunina, Z. F. (1960) High School News Food Technology, No.2, p.63. Changes in the dough and bread colloids, in particular the bound-water content of wheat and rye doughs during the various technological phases of production and storage are presented in Fig. 144. This shows that an increase in bound-water content occurs at two stages during processing: in the sour/sponge before final-dough mixing, and during baking, whilst the loaf remains hot. Knjaginicev observes that the increase in bound-water during the pre-ferment stage is due to the increased hydration capacity of the proteins, coupled with the increased acidity-index on ripening (lower pH). Initially during baking, the bound-water increases, but decreases as the proteins become denatured. However, when the starch gelatinizes, the bound-water increases again by virtue of the starch, at the expense of the proteins. The general pattern of the curves (Fig. 144) for wheat and rye processing is similar, but the rye curve (1), is appreciably higher in overall water-binding capacity. This difference is due to the much greater pentosan content of the rye, and the colloidal properties of its proteins. In bread, starch and water make up 80--85% of its contents, the sugars, cellular material, lipid and mineral salts being relatively small. The chemical structure of these minor components are such that they exert little influence on the hydrophilic properties of the bread. Whereas, the hydration capacity of the proteins, amounting to 8% or more, have a great influence on the hydrophilic properties of the dough, determining bread volume, crumb porosity and elasticity. The cellular content of the rye meal, consisting mainly of arabinans and xylans, have a great influence on both the colloidal properties of the rye dough, and bread. During baking, these pentosans become denatured, but as far as the physical-chemical properties of the flour and bread components are concerned, whenever the nature of the staling process is under investigation, only changes in the starch and protein have received attention. Refreshment of bread with a moisture content of 30% and above by heating has been long known, and if the moisture is below 30%, it can be refreshed by first dipping in water for a short time. Evaluation of the degree of staling usually only involves a sensory appraisal of the organoleptic properties, but Knjaginicev also studied the changes in crumb-swelling over a 24-hour period at various temperatures. His results confirmed the importance of the hydrophilic, high-molecular-weight polymers (colloids), the crumb losing its ability to swell with staling. Crumb swelling over 24 hours was found to be a maximum at 60°C, when the bread was sensorically judged as 'fresh', and reached a minimum at O°C, when it was judged as being 'completely stale'. Bread stored at - 30°C was judged as completely fresh, and the crumb swelling almost reached the 'fresh' state maximum value. Table 72 shows the crumb• swelling data at various storage temperatures during 24 hours, and the corresponding sensory evaluations. Freshly baked bread, stored within the temperature range 60 to 90°C, or -20 to -190°C remains in the fresh state due to a successful retardation of the staling processes. Temperatures between 50°C and - 7°C, including room or ambient temperature range, are unfavourable in this respect. Although the part played by storage temperature in the maintenance of freshness has not yet provided a full clarification of staling, investigations of changes in physical-chemical properties conducted parallel with any retardation-process• development can yield further information concerning bread components and their response. Starch, which contributes 50% to 60% of the composition of bread and baked products, consists of about 20% amylose and 80% amylopectin. These components differ in both their molecular weight and their chemical behaviour, being arranged differently within the starch granule. Some areas within the granule are discretely organized with a crystalline space• lattice X-ray pattern spectrum; other areas are randomly organized, according to Badenhuizen. Notes and references 815

Badenhuizen, N. P. (1971) Structure and formation of the starch granule. In Starch Handbook, Paul Parey, Berlin and Hamburg. Interference patterns of the rays show restricted sharpness in the contours of the rings of the X-ray pattern. Rye-bread shows a wide, diffuse ring, similar to completely gelatinized wheat starch. Water content is also reflected in the X-ray spectrum, starch at atmospheric moisture levels conforming to the native starch spectrum; water-free starch exhibits a pattern similar to amorphous starch. Interference patterns of the X-rays show a strong dependence on the starch water absorption, in the case of crystalline starch, water is built into the lattice in the form of hydrogen bonds. In flour, starch particles only bind water at the surface by adsorption at 20°C, any hydration only starting at the damaged areas of the granule. During baking, the energy input results in granule swelling, water resting between the amylose and the amylopectin molecules, both organized and randomized areas becoming hydrated. Spatial arrangements remain intact during this swelling process. Network bondings being typically hydrogen bridges, and van der Waals force bonds, which become partially broken during hydration; the hydrated starch molecule at temperatures above 60°C is the energy• stable form. Starch cooling results in the system becoming thermodynamically unstable, and staling or 'retrogradation' progressively commences. Retrogradation is applied to reactions taking place in the aqueous starch suspension, in addition to those in the crystalline state, including the ageing of amylose and amylopectin. Immediately after baking, the amylose is mainly colloidally dispersed, and the amylopectin in the swollen globular state. Cooling involves a process of partial crystallization, the formation of a structured gel; then crystals of amylose and amylopectin, and mixed crystals form, which progressively form an increasingly firm mechanical structure. Speed of crystallization depends on the ratio of amylose to amylopectin, and the molecular orientation of the components. Wheat starch crystallizes more rapidly than potato starch, hence the use of the latter to retard the entire staling process. The stability of colloidal systems depend on particle aggregation, as is the case with the starch granule. Both amylose and amylopectin become surrounded by thick water layers known as 'hydration-shells', or 'solvation-shells'. Mutual contact is prevented by surface charges, shell repulsion determining their spacing. The repulsive force depends on the dimension of the hydration-shell, and the magnitude of the electrical charge. The ability to form hydrogen bridges is very significant in the case of starch, depending on the steric formation of the molecule; amylose is capable of assuming various helical conformations in solution, as pointed out by French. French, A. D. (1979) Bakers Digest, 53, 1, p.39. Hydrogen bridge formation in amylose and amylopectin is schematically illustrated in Fig. 148. Retrogradation results in the formation of a space lattice structure from amylopectin, inside which the retrograding amylose becomes engulfed, which explains why a reduction in the soluble amylose occurs after about 2 days' storage. Also, according to Knjaginicev, during staling, the water molecule becomes subjected to a molecular reorientation, due to its four charges. One water molecule, depending on its four charges, can orientate four other water molecules, forming an aggregate of five molecules as an hexagonal lattice with loose spacing (as in ice formation). A denser spacing is made possible by a reorientation of the hexagonal lattice to form a tetragonal one, or owing to filling of vacant spaces with more water molecules. Fig. 146 shows the proposed Knjaginicev model in schematic form, depicting how, during dough processing, the flour forms with water, under limited swelling, a viscoelastic gel. Only part of the dough water participates in the swelling of the polymers. Mechnically bound water is depicted as dots and arrows. Initially, the dough polymers in the form of a swollen gel are unstructured, forming a one-phase system. Dough-heating during baking favours diffusion of water into the intermolecular spaces of the starch and proteins. This results in the macromolecular monomers, viz. sugars and amino 816 Handbook of breadmaking technology

acid residues, becoming mobile, losing their initial compact posture. Thus, macro and micro hollow cavities develop, and under the influence of higher temperature, the proteins coagulate, forming a framework, and fixing the porous volume ofthe bread. The crumb cell• walls, consisting of starch and protein, constitute a swollen system in which one part of the water is thermodynamically bound, and the other part distributed in the intermolecular spaces of the denatured proteins and the swollen partially gelatinized starch. In effect, both the dough stage and the baking dough-piece constitute a swollen, elastic, structureless gel. On removal from the oven, owing to the flexibility of the starch monomers, the molecular chains move closer together, and intermolecular van der Waals force bonding results in the formation of a mechanically firm network, i.e. a structured gel. This completes cooling and setting of the loaf. Bread staling processes result in this network progressively reaching a maximum state of mechanical firmness. Knjaginicev postulates that the water in the macropores is probably not in the free state, but rather exists in an ordered form owing to the high polarity of the molecules, and the electrostatic forces at the surface of the micropores. The walls of these micropores consist ofthe macromolecular starch and proteins, as schematically illustrated in Figs 145 and 146. Eventually, the water, starch and proteins form a uniform structured system. Refreshing the bread by heating results in the water structure within the pores of the crumb being destroyed, according to Knjaginicev, and the macromolecular chains reverting to the freshly baked state, as shown schematically in Fig. 146, 4 to 3, then to 2. Thus depicting the stages of swelling and gel formation, depending on the state of the water molecules. Knjaginicev's bread-crumb staling model represents a revision of former postulates, in order to present a more realistic approach to the questions posed by bread staling. The basic concept is the formation ofa structure within the micropores of the starch and protein polymers of the bread as a result of the reorientation of the water molecules. The resulting aggregates forming an hexagonal space-lattice, similar to ice, but loosely packed. As staling proceeds, the spatial density becomes compacted, either owing to reorientation of water molecules to form a tetragonal lattice, or as a result of water molecules entering the empty spaces within the lattice. The crumb is thus transformed into a firm structured state, the main participant being the water molecule, its mobility and colloidal activity. Storage of bread within the temperature range 50 to - 7°C results in both the starch macromolecules, and the water molecule losing their mobility, giving rise to a firm structured system. Additional tests, involving the addition of starch granules to white bread before baking confirmed that similar moisture losses occurred after 4 hours and 8 days, both in the added starch and the bread• crumb. Therefore, there is no appreciable migration of water from the water-rich crumb to the water-free starch. Knjaginicev consequently concludes that the crumb consists of a system of pores with cell-walls of starch and denatured proteins in a swollen state; within which the water is in part thermodynamically bound, and partly distributed within the intermolecular spaces of the proteins, and swoIien, partially gelatinized, starch. The molecules of water, starch and proteins forming a uniform structural system. During the refreshing of staled bread by heating, the structure of the water within the micropores of the crumb is disturbed, and the starch and protein macromolecules revert to a state similar to that of fresh bread. Polymer crystallization principles have been applied to the study of starch retrogradation, since it has been widely accepted that it involves a crystallization process. Avrami, M. (1940) J. Chem. Phys., 8, p.212. Avrami, M. (194J) J. Chem. Phys., 9, p.l77. Cornford, S. J., Axford, D. W. E., and Elton, G. A. H. (1964) Cereal Chem., 41, p.216. Sharples, A. (1966) Introduction to Polymer Crystallization, Edward Arnold, London. Kim, S. K., and D'Appolonia, B. L. (1977) Cereal Chem., 54, p. 216 and 225. Elton, G. A. H. (1969) Bakers Digest, 43, 3, p.24. Notes and references 817

Axford, D. W. E., et al. (1968) J. Sci. Food Agric., 19, p.95. McIver, R. G., et al. (1968) J. Sci. Food Agric., 19, p.560. Krilsi, H., and Neukom, H. (1984) Die Starke, 36, 2, p.40-5 (German). Soluble starch extractionfrom bread crumb has also been applied to the measurement of the degree of retrogradation (staling). Kim, S. K., and D'Appolonia, B. L. (1977) Cereal Chern., 54, p.207 and 216. Amylose/amylopectin ratios, and their rates of retrogradation have also been the subject of research. Neukom, H., et al. (1981) Lebensm. Wiss. und -Technologie, 14, p.292 (German). Protein/starch ratios, and their exchange reactions in the presence of ions, have also been considered to participate in bread staling processes. Erlander, S. R., and Erlander, J. G. (1969) Die Starke, 21, 12, p.305. Protein physical-chemical changes during bread storage, as a result of ionic bond and hydrophobic-ionic interactions, have also been linked with the staling processes. Kolpakova, V. V., Nazarenko, Y. A., Zharinov, V. I., and Burak, I. A. (1987) (USSR) Mlyn-Pek. Prum. Tech. Skladovani Obi/i, 33, 11, p.321-3 (Czech). Gluten/starch moisture exchange mechanisms, have been variously proposed by some researchers. Cluskey, J. E., et al. (1959) Cereal Chern., 36, p.236. Willhoft, E. M. A. (1973) Bakers Digest, 47, 6, p.14. Flour gluten-protein quality and adequate fermentation in bulk, and after shaping, have also been found to influence staling rates. Maleki, M., et al. (1980) Cereal Chern., 57, p.138. Starch energy levels in the amorphous and crystalline states, and the availability of external heat energy, has been linked with gelatinized starch retrogradation. Senti, F. R., and Dimler, R. J. (1960) Bakers Digest, 34, 1, p.28. Dough-enrichment raw materials, containing various protein sources such as soy, gluten, ground-nut, and non-fat milk solids, will reduce crumb-firming rates, but have little effect on the ageing of the crust, which loses its crispness, becoming elastic and tough. This latter trend is due to moisture exchange with the crumb, as is the case with unenriched bread. Non-starch polysaccharides such as cellulose, pentosans, hemicellulose, beta-glucans, mannans, gluco- and galactomannans (pectins), also glycoproteins, all constitute a group of substances which have an effect on dough and baked products, right through to the staling processes, on account of their chemical, physical and rheological properties. Wheat-flours can contain 3--4% of these substances, depending on the extraction rate, some of which are 20- 25% cold-water soluble. Rye-flours contain about the same levels at low extraction, but the cold-water soluble fraction is about 40%. Studies of the effect of pentosans on staling rates, concluded that they slowed down the rate of crumb firming, especially the water insoluble fraction. Kim, S. K., and D'Appolonia, B. L. (1977) Cereal Chern., 54, p.225. The water-soluble fraction of the pentosans reacts with the starch amylopectin only, but the insoluble fraction retarded and retrogradation rate by interaction with both the amylose and amylopectin. Kim, S. K., and D'Appolonia, B. L. (1977) Cereal Chern., 54, p.150. The presence of the pentosans tends to reduce the exposure of the starch components to crystallization during staling, acting like a protective-colloid. Protective-colloids owe their stability and high viscosity to their hydration-shells, giving rise to the formation of large particles. Gilles and co-workers found pentosans in the soluble-starch fraction of the bread-crumb; the 4·3% soluble starch extracted from fresh bread-crumb contained 11·7% pentosans. This 818 Handbook of breadmaking technology

compared with 3·3% soluble starch extracted from stale bread-crumb, of which 19·3% was pentosan. This increase in relative amount of pentosans in soluble starch with bread staling is attributed to the crystallization of amylose and amylopectin. Since pentosans have been shown to retard amylose retrogradation, the decrease in soluble starch due to staling is considered to be essentially the result of the aggregation of amylopectin. Gilles, K. A., Geddes, W. F., and Smith, F. (1961) Cereal Chem., 38, p.229. Instrumental physical techniques applied to the study of mechanisms of starch gelation and retrogradation (staling) include: dynamic/mechanical thermal analysis, involving a torsion rheometer system, providing viscoelastic data, viz. steady shear viscosity, complex viscosity, complex modulus, elastic modulus, loss modulus, and damping of low viscosity materials; differential scanning calorimetry (DSC); X-ray diffraction; Fourier transform IR (FTIR) spectroscopy. The time course of FTIR measurements during storage retrogradation of starches is similar to that produced from shear modulus tests. This method being applicable to starch gels, and real foods, e.g. commercial bread. DSC techniques are frequently used to study the effects of various emulsifiers and crumb softeners on bread staling and starch-gel ageing. Eliasson, A. C. (1985) Prog. Biotechnol., 1, p.93-8. New approaches to research in cereal carbohydrate. The DSC endotherms of stale bread or aged starch-gels provide amylopectin melt read-outs. The size of the endotherm increasing with increasing storage temperature and time. The addition of sodium stearoyllactylate to starch gel decreases the staling endotherm. Amylose/ lipid complexes affect the crystallization of amylopectin. DSC endotherm measurements do not monitor the same changes in ageing starch gels as those measured during gel strength tests using compression methods in the elasticity mode. Measurement of water concentrations in the free and bound state is possible with NIR spectroscopy, utilizing specific bands at 1940 and 1450 nm. The band at 1450 nm can be resolved into two discriminant spectral patterns at 1410 and 1460nm for proportions of free and bound water. The application of nuclear magnetic resonance (NMR) techniques are also becoming increasingly important for the study of aggregate and binding states in solid/liquid food systems. Nuclear resonance impulse spectroscopy can be applied to the measurement of diffusion coefficients during drying-out processes, and molecular exchange reactions. Moisture redistribution between bread components during staling is a possible application for NMR studies. Chemical procedures applied to studies of the staling processes often include the following: soluble starch/amylose determination/g starch with time; saccharide analysis; protein extraction and resolution; pentosan extraction and resolution; presence of gluten/starch complexes; presence of starch/lipid inclusion complexes. Banecki, H. (1970) Congress Report No.5, World Wheat and Bread Congress, Dresden, Vol.5, p.179. Hiittinger, R. (1972) Gordian, 72, 7/8, p. 261. Emulsifiers in baking. Erlander, J. G. (1969) Die Starke, 21, 12, p.305. Explanation of the ionic in connection with various phenomena. Protein/Carbohydrate exchange reactions, and the mechanism of bread staling (English). Acker, L., et al. (1968) Getreide und Mehl, 18,6, p.45. Wheat lipids (German). Acker, L., et al. (1974) Getreide Mehl und Brot, 7, p.181-6 (German). Effects of fermentation schedules and storage-time on sensory evaluation and volatile compounds in white bread crust and crumb, were investigated by Stoellman. Stoellman, U. M. (1986) Shelf-life foods and beverages. Developments in Food Science, Vol. 12, p.293-301. Iodine-binding intensity of amylose and amylopectin have been used to monitor the staling of baked products. Hampel, G. (1969) Brat und Geback, 23, 6, p. 106. Investigations of the staling-processes in baked-products (German). Notes and references 819 CHAPTER 3.6 DOUGH AND BREAD PREVERVATION

Retardation of staling processes has been most successfully achieved by freezing and the application of cryogenics, which represents the closest approximation to 'oven-freshness' in the case of most baked products produced by fermentation. Anti-staling agent application is restricted by food safety regulations, and has been increasingly restricted to natural raw materials, and their modifications. These substances can be grouped as follows: protein, carbohydrate, cellulosic-based; enzymes and enzyme• containing substances; shortenings and emulsifiers; aliphatic and cyclic aldehydes, which locate between the hydroxyl groups of the starch and protein, anti-staling function increasing with chain-length. Dough Improver/conditioner mixtures are manufactured in powder, paste, dispersion or tablet form, consisting of blends of emulsifiers, enzyme preparations, shortenings, malt-flours, sugars, hydrocolloids, with a carrier material. Often, ascorbic acid is added, with or without other permitted oxidants to form a complete processing-aid. See Section 1.5. The most widely accepted emulsifiers are the phosphatides, of which the lecithins are the commonest. These polar lipids form complexes with the amorphous starch fraction, the presence of non-polar groups prolonging hydration of the crystalline regions of the starch granule. Phosphatides are also highly functional when used in combination with vegetable oil and water in the ratio 5:5:90 in emulsion form. This emulsion, at 0'05% flour weight is then combined with 0·3% of enzyme-active full-fat soy-flour (flour weight), as a source of active lipoxygenase, and made into a dough with wheat-flour, yeast, salt and water in the usual manner. The soy-flour is ideally first dispersed in a portion of the dough water to release the lipoxygenase into solution. The mechanism of the functional reactions is the oxidation of the polyunsaturated fatty acids of the vegetable oil, and the phosphatide emulsion concentrate by the lipoxygenase and the entrapped oxygen. The resulting hydroperoxides act as nascent or 'active-oxidants', reacting with the SH-groups of the protein-proteinase complex of the wheat-flour. This reaction improves the gas- and structure-retaining capacity of the dough, resulting in bread with improved volume, symmetry, texture and crumb elasticity. Also, the peroxides of the fatty acids oxidize and bleach the carotenoid pigments, giving rise to a brighter crumb colour. This technique is a cost-effective method of processing untreated/ unbleached wheat-flour with successful results, and satisfying a 'clean-label' legislation requirement. For the preparation of the so-called 'liquid oxidation phase', which can be on a batch or continuous basis, about 50-75% of the total dough water is utilized; and in the case of a pre-ferment sponge, all the water is normally used in its preparation. Auerman, L. J., Kretowitsch, W. L., Polandowa, R. D. Process for the quality improvement of wheat bread. USSR State Committee for Inventions and Discoveries, Patent No. 164860, with priority from 8: 7: 1963 (Russian). Auerman, L. J., Kretowitsch, W. L., Polandowa, R. D. PrBchMb, 1, 1,66, 1965 (Russian). This process results in a considerable improvement in dough rheology, improved water binding, and a more rapid dough ripening owing to acid build-up. This process is similar in conception to the Blanchard process, but not in practical execution. Enzyme-activefull-Jat soy-flour is a cost-effective, safe, anti-firming agent of quality and long• standing. The addition of 0'5%, based on flour weight, reduces the crumb-firming rate of bread by reducing the rate of moisture interchange between starch and gluten proteins. The average composition offull-fat soy-flour is: protein 41 %, lipid 20%, moisture 5%, and about 3% pen to sans, which also contribute to dough water-binding capacity. Defatted soy-flour has a reduced beany flavour, and inactivated enzymes, as a result of heat treatment. This material can be used at levels of of 3-5% flour weight, and as a nutritional supplement, especially for the amino acid lysine, deficient in wheat-flour. Detailed information concerning dough improver conditioners can be found in Section 1.5. 820 Handbook of breadmaking technology

Packaging materials with the appropriate properties can offer considerable retardation of staling by hindering dehydration and preventing the partial water pressure from causing progressive moisture loss to the atmosphere. The degree of staling retardation depends on the choice of packaging material; however, since no material can satisfy all requirements, a compromise is found between price and functionality. Waxed paper was the only material used for bread for many decades, being first coated with paraffin-wax, but later this was blended with microcrystalline wax and polyethylene resin to improve appearance, elasticity and sealing properties. The advantage of paper was ease of imprinting for labelling purposes. Cellophane films gained wide acceptance in the late 1930s, first being a film or sheet of a defined thickness and hence strength. Cellophane was improved by the application of coatings of either nitrocellulose or polyvinylidene chloride, which contributed to its resistance, gas permeability, heat• sealability, and moisture vapour transmission rate (MVTR), also acting as an oxygen barrier. It is an excellent material with wide application, but relatively expensive. Plastic polyolefinfilms, e.g. polyethylene and polypropylene, replaced Cellophane (cellulose) films during the 1950s for certain product applications. They differ in tensile strength, rigidity, permeability, and temperature-sensitivity. Various manufacturing methods provide a wide range of films of various gauges, orientations (cast/unbalanced), coatings, and laminate combinations. Polyethylenefilm, available in high, medium and low densities, is the most popular packaging material for bread and rolls, the standard low-density film being the basic material for perforated bags. For greater heat stability, a medium density film is appropriate. Polypropylene film has similar properties, but is more rigid and stronger at the same gauge or thickness. It can also be used as a component in laminated films to provide stability at heat• sealing. Special inks and printing techniques provide a range of colours and designs for marketing. Hoffmann and co-workers in the GDR, found that the use of different packaging material gave different improvements in moisture retention. Hoffmann, R., et al. (1976) Extending the freshness of bread, rolls, and specialty products. Part I: Bread and rolls. Research report IGA, A4, Bergholz-Rehbrucke, GDR (German). Improvement in retention offreshness with aluminium-polyethylene bags was maximum 23%, polyethylene-coated paper maximum 16%, and polyethylene film maximum 9%. Rapidity of staling was also found to depend on storage temperature and RH. In the case of mixed rye/ wheat bread (Mischbrot), storage at 20 0 e for 24 hours gave crumb-firmness equivalent to that at 28 hours when stored at 30°C; and at 60°C, crumb firmness at 48 hours was comparable with that at 16 hours at 20°C. Crumb firming reaching a maximum at 4°C. Packaging material criteria for the baker are: degree of product protection; performance on existing packaging-machines: attractiveness of the package to the consumer, to keep ahead of competition; justification of cost. Polyolefin films have now become the established material for bread, and the orientated polypropylene for sweetened products. Coated orientated polypropylene find application in overwrapping products in trays and cartons. Aluminiumfoil is used for specialty products, where a low moisture transmission vapour rate (MTVR) and oxygen transmission rate (02TR) is required. The cost is, however, about two to three times greater relative to polyethylene. Prevention ofmicrobial infection in all storage and dispatch areas is a prerequisite, and general maintenance of cleanliness and hygiene practices by personnel within production, storage and dispatch is essential to avoid cross-contamination. Transportation containers, operative's clothing and wash areas must be regularly cleaned and disinfected. Airborne spore-counts within the bakery must be reduced to a minimum. Where air-filters are installed, areas must be hermetically sealed, and the air cooled before entering the filter. Filter Notes and references 821

efficiency also depends on filter design, size and electrical charge of particles, their temperature, RH, and degree of air pollution. Air drawn into the bakery should be UV• irradiated by wall-mounted units at a height of about 2 m. Spores passing within about 3 cm of the irradiation source, as a result of convection currents are destroyed, provided the rays strike them at right-angles. Equipment can also be UV-irradiated, but personnel must be provided with green-filter goggles, or the irradiation carried out in their absence. Bread-slicing and -wrapping departments must be kept under a strict hygiene regime at all times. Only people working therein should have regular access; temperature 18-20°C and RH 65% should be automatically regulated; personal hygiene and regular medical check-ups for personnel are essential disciplines. Optimal fermentation and process control can also help to prevent microbial infections, and premature onset of staling processes. Adherence to adequate yeast levels (about 2% flour weight), and use of dough temperatures within the range 22-26°C, allows doughs to mature for a maximum time, depending on flour quality, and will hinder the establishment of airborne fungal or bacterial spores. Maintenance of dough pH within the 4·8 to 5·0 range for wheat-flour, and final bread acidity-index of 12 for rye wholemeal flour doughs, will hinder any incidence of B. mesentericus (potato bacillus) or B. subtilis (hay bacillus). These species are broadly distributed in air, soil and plants, and can be found in grain and flour on occasion. Since these bacilli survive the baking process, and liquefy and destroy the crumb structure, their optimal conditions of reproductive growth must be avoided. In the case of dough-sours, this can be done by increasing the souring intensity of the basic-sour, or in both yeasted wheat and soured rye doughs by the addition of an appropriate amount of lactic or acetic acid. In this respect, a target pH of 3·8 in the final dough should solve the problem. Chemical preservatives or mould inhibitors are widely applied in countries where legislation permits. They include salts of propionic and acetic acids, and sorbic acid and sorbates. In the USA, a maximum of 0·32% sodium propionate, 0-4% sodium acetate, or 0·75% calcium monophosphate are applied, all based on flour weight. Sorbic acid used at the 0·1 % flour weight level is a very effective fungistat, owing to unsaturation in molecular terms and lower dissociation constant in solution. Where shortenings are used, it can be added to the dough after premixing with the shortening to avoid yeast inhibition. Hickey has suggested a spray application of 1·0-1·5% potassium sorbate solution on hot, freshly baked bread, rolls, and partially baked products, as effective in doubling or tripling the mould-free shelf-life of the products. This gives sorbate residuals of 0'02%, based on flour weight. Hickey, C. S. (1980) Bakers Digest, 54, 4, p.20. Schulz has suggested the use of dough sours combining lactic and propionic fermentation, by using special cultures of propionic acid bacteria. This resulted in a prolongation of bread moulding to 14-19 days, without affecting either the flavour or volume of the bread. Schulz, A. (1959) Brot und Geback, 13, 7, p. 141 (German). The continental European practice of using relatively high initial baking temperatures, known as 'vorbacken' (German), resulting in early crust formation, is recommended for hearth breads. This is then followed by extended baking at a lower temperature. Pasteurization/sterilization of bread and baked products. Heat sterilization of specialty sliced breads, such as pumpernickel, is achieved either at high temperature, or by the utilization of energy-rich ionized radiation. Sterilization within the packaging gives the best guarantee for prolonged mould-free shelf-life, providing the packaging material has been previously sterilized, and no subsequent contamination takes place. The process depends on temperature and time. At 150°C, a sterilization time of 15 minutes is normally sufficient; but at 98°C, an exposure-time of 12 hours is necessary to obtain the same degree of sterilization. High-frequency microwave heat sterilization permits exposure-times of 10 seconds to 2 minutes, depending on the type of product, dimensions, and packaging materials used. An 822 Handbook of breadmaking technology average schedule could be 2 hours at 90°C for a 250-g sliced bread pack. Owing to the effect of temperature the package shrinks, and the overlapping film must be immediately sealedJrom external contamination. Heat treatment is normally carried out in a tunnel, heated either by gas or electricity, positioned downstream of the packaging-machine, but adjacent to it. A temperature gradient always exists between the inlet and outlet end of the shrink-tunnel, the packages being transported through on a band conveyor. The heat-stability of the packaging material is often the limiting factor for the choice of the sterilization temperature. On exceeding a certain temperature, most materials become brittle or melt. The application of microwave heating will not allow the use of metallic packaging materials, coated polyethylene films being more appropriate. Such techniques are routinely only applied to specialty products such as pumpernickel and whole-grain meal breads, e.g. Vollkornbrot, which have a dense, close texture. Breads made from low extraction wheat-flours with higher volumes, and porous textures could suffer damage from heat sterilization processing. Burg has described a tunnel microwave sterilizer designed for 400 to 600lb bread capacity. Burg, F. (1968) Brot und Gebiick, 22, p.58 (German). Sterilization takes place by conveying the packaged bread through the tunnel with a residence-time of 45-90 seconds. In such cases, a moisture-permeable wrapping material has to be used, since the shock treatment results in some moisture release within the packs. Another solution is to use a moisture-permeable material, followed by an airtight packaging material; or opened plastic bags can be used, the bags then being sealed on completion of sterilization and moisture evaporation. IR-sterilization for bread and baked products, has been described by Zboralski; it offers technical and economic advantages, being first applied in France in 1965, for sliced bread and cake. The process utilizes IR rays in the middle range of the spectrum (2500 Angstrom degrees), the radiation being absorbed by the product, and transformed into heat, temperatures of I6D-I70°C being attained. Important for the success of this process is the packaging material, a high-temperature stable special polyamide foil (nylon-type) being most suitable, together with a low vacuum. The packaging material must be heat-stable up to 200°C for the duration of sterilization; it must be steam-proof, gas-proof and impervious to spores; have good heat-sealing capability; and allow penetration of the IR-rays without loss of energy. Zboralski, U. (1973) Getreide Mehl und Brot, 27, 6, p. 213-16 (German). The necessary requirements were only satisfied by a stabilized film from Polyamide 11 ('Rilsan'), available in tubular form of 4D-60 J1m strength. The product is placed in the bag by special equipment, and then packed under a low vacuum with a vacuum sealing machine, adjusting to avoid product deformation. The advantage of the IR-sterilization process is the extremely short time required compared with heat-convection processes. This is due to a two• stage process of heat-transfer. The IR-rays penetrate a few millimetres into the product, and become almost instantaneously transformed into heat energy. This in statu nascendi liberated energy can achieve temperatures of about 300°C, but rapid conduction distributes heat throughout the product interior, the centre rapidly attaining 7D-80°C. The product surface also receives a rapid energy transfer, resulting in a reduction in sterilization-time of 50% compared with hot-air sterilization. To facilitate heat control, the tunnel is normally divided into three heat-zones (See Table 73.)

X-ray, beta- and gamma-radiation, techniques have also been successfully applied to bread preservation. Warming of rye/wheat breads to 50°C, and irradiation with 0·05 Mrad, permits preservation for several weeks, without sensory devaluation. Stehlick, G. (1968) Atompraxis, Karlsruhe, 14,4/5, p.l. Gamma-rays on bread (German). For the application of ionized radiations for preservation, specially treated polyethylene has proved a suitable packaging material. Although preservation by ionized radiations has not yet become widely acceptable, owing to the potential health hazards-mainly due to induced radioactivity-the energy levels used are too low to result in radioactivity in the product. The maximum irradiation dose likely to be permitted generally, as a result of the WHO Notes and references 823

recommendation published in 1981, is lOkGy (0·005kGy=0·5Gy=50rad). Extent of penetration depends on product density, and electron beam energy. In The Netherlands, all foods can be irradiated up to the 10 kGy dosage level, which substantially reduce the microbial load, and the number of non-sporing pathogens. For sterilization, higher doses can be used commercially. Clearances by the Atomic Energy Agency in Vienna, have been granted for rye bread sterilization in The Netherlands and USA, and for wheat and wheat• products in USSR, Canada, Brazil, Spain, Chile, Thailand, and Bangladesh. Official Journal of European Communities, No. C99, 13:04:87. Various claims against irradiated foods on grounds of safety hazards, and carcinogenic residues have been investigated by the WHO/IAEA/FAO, and rejected. For food products, the accepted radiation unit is the 'gray' (Gy), which is defined as the amount of radiation absorbed by 1 kg food, equivalent to 1 joule of energy; 1 kGy = 1000 Gy. Considerable confusion exists between 'radioactivity' and food preservation by the technique of 'irradiation'. Irradiation is a physical method of food preservation, using ionizing radiation, ionizing in the form of short wavelength electromagnetic energy, e.g. X-rays. Resulting free radicals lead to the destruction of microbial DNA, but the dosage levels are too low to induce radioactivity in the product. Also, in the practical execution of these techniques, the food never contacts the radioactive source, e.g. 60Co, or 137 Cs, therefore, there is no chance of the food becoming radioactive. Currently, there are two main forms of ionizing radiation 'commercially applied. Gamma-rays emitted by radioactive sources such as cobalt-60 or caesium-137, in which case the food never contacts the source, hence no chance of the food becoming radioactive; and the use of high energy electrons in the form of electron beam irradiation, which does not require a permanent radioactive source,' and is therefore environmentally attractive. Its application is, however, limited by the relatively weak penetrating power of the electrons, being only suitable for foods up to about 10cm thickness. The application of X-rays is under current research, but no commercial X-ray irradiators are presently available. Packaging ofbread, although having little effect on the chemical staling processes per se, does reducc the rate of crumb-firming compared with unwrapped bread, and also provides a hygienic barrier for handling. Martin, C. W. (1944) Food, 13, p.129. Cathcart, W. M. (1940) Cereal Chem., 17, p.100. Sliced bread packaged in a moisture-proof material only lost about 2% during 72 hours, owing to a state of equilibrium being reached between crumb and crust. Unwrapped bread loses moisture mainly from the outer 13 mm of crumb, already at 24 hours, forming a dry crumb adjacent to the crust. Wrapping-temperature, is an important parameter both for keeping properties, and for sensory characteristics. Berg concluded that warm wrapping at 45°C gave the best crumb softness after 36 hours storage, but resulted in severe loss of aroma and taste. Conversely, cool wrapping at 31°C gave the greatest loss of crumb-softness, but the best retention of aroma and taste. These results, however, refer to high-specific-volume panned bread, and cannot be applied to hearth-breads. Berg, I. A. (1929) Am. Soc. Bakery Engrs Bulletin, 39. Hearth breads should have a maximum temperature at the crumb-centre of 40°C, and where cold slicing is the chosen procedure, crumb-centre temperatures should fall within the range 20-25°C. European experience indicates optimal bread maturing-times of 2 hours for warm slicing at 40°C in the case of wheat bread, and 3 hours for rye and rye/wheat bread types. Wrapping of hot, crusty hearth-breads in the unsliced form can be successfully achieved by using a 360 micrometre, perforated polypropylene film, which is available as a centre-folding film on the reel, or as bags. Alternatively, a new white-pigmented, biaxially orientated polypropylene film, 35 micrometres thick, and co-extruded on both sides with polyolefinic copolymers, has been found ideal for specialty-breads. This is due to excellent water-vapour 824 Handbook 0/ breadmaking technology

retention properties and UV-light transmission, being heat-sealable on both sides. Since many compounds from packaging materials can migrate into food products, the legal consequences of resultant interactions for food quality and consumer protection should be evaluated. Piringer, O. (1988) Chern. Ing. Tech., 60, 4, p. 255-60 and 265 (German). Interactions between Food and Packaging. Fraunhofer Inst. Lebensmittel-technologie und Verpackung, D-8000 Munich 50, FRG.) Review of 14 references. For the packaging of bread and rolls, intended (or fresh consumption, or consumption within 1 week of baking, the slicing-room atmosphere must be kept as spore-free as possible, and packaging materials, machines, and their blades kept clean and sterilized. If these basic regimes are adhered to, the packaging of baked products should prolong their shelf-life by a factor of two to three times that of unpackaged products.

3.6.3 Dough Preservation by Freezing Although the application offreezing technology to baked products remains important for the baking industry, of far greater significance is its application to doughs. This technology has revolutionized the working schedules of production, and facilitated forward-planning of inventories, and their distribution to wholesale and retail outlets. This sector of the industry now includes the large and small frozen-dough product manufacturer, and the ever• increasing number of non-manufacturers in the wholesale and retail market, who are' described as 'bake-off' bakeries or retailers. Whether defrosted and warmed up in the case of baked products, baked-off domestically, or baked-off by a retailer or in-store bakery as a frozen dough-piece, the eating quality of the final product has the 'fresh' characteristics. Prepared and shaped dough-pieces for a wide variety of baked products, can be blast-frozen at high volume output with a core temperature of - 20°C within 20 to 60 minutes, depending on product mass. For smaller output requirements, tray-loading freezers offer similar results at about one-third of the cost of a tunnel-freezer. Such heavy-duty units are suitable for fermented products, gateaux, and pastries with mass up to 400 g. The frozen products are then transferred to a low-temperature holding cold-room. Once frozen, the dough-pieces must be maintained at - 18 to - 21°C, until required for the retarder-proofer, for gentle adjustment to the retardation temperature state, and subsequent proofing. Distribution to receiving bakery outlets is by refrigerated vehicle, and once the frozen items are received, they are held either in a freezer cabinet/room or retarder-proofer, depending on the operation. The advantage of a retarder-proofer unit is that the dough-pieces can be stored and gently brought to a retarded state until required, at which point, proofing can be initiated ready for bake-off. Retarder cold-rooms can be employed, set at 2°C for overnight storage, or -4°C for 72-hour storage. Retarder cabinets are used in smaller outlets, which combine both temperatures, selected at the flick of a switch. The important concept of freezing-process technology in the bakery is that one can separate in terms of time and place the dough preparation and fermentation from the bake-off process. Retarder-prooJers combine the benefits of dough-retardation with an automatic pre-heat, recovery and proofing facility, thus minimizing early-morning preparation work. The baker arrives to a cabinet full of ready proofed dough-pieces ready for the oven. To enable the baker to process products of diverse weight and variety in pre-prepared, and shaped form, retarder• proofers have a built-in manual control option for the adjustment of retard, recover, and proof periods, as well as temperatures. These functions are operated from a central control• panel, covering such typical ranges as: + 2 to - 4°C for retarding; - 8 to + 3°C for automatic pre-heat; 3 to 24°C for recovery; and 24 to 43°C for proofing, with adjustable humidity. Dough retarders permit the baker to produce dough-pieces in advance, and retard ready for proofing and baking off, either the following day or at a later date, thus eliminating early• morning preparation and setting up an inventory of products which can be drawn on as demand arises. Product inventories are built up during off-peak periods. The baker is not Notes and references 825

limited to overnight or short-term retardation, both rich and lean formulated doughs can be retarded for up to 72 hours, thus bridging weekends and short vacational periods. Adjustable thermostats allow the baker to reduce dough-piece temperature from 27°e to -4°e within 1·5 to 3-0 hours, and for overnight storage, retardation at + 2°e is adequate. Retarding to a stabilizing temperature of -4°e, which is still above the dough freezing-point, allows extended storage for up to 72 hours; and at - 10oe, up to 7 days storage is possible. Storage freezers are intended for extended storage of dough or baked products, thus allowing the build-up of a back-up inventory to cope with unexpected or variable sales demands. These units operate at temperatures of -18 to -21°e, and are normally fitted with an automatic defrost plug-in facility. Storage times can be days or weeks as required. Blast freezers are based on a modular (block) construction principle, to meet individual requirements for a larger capacity operation. Multi-tunnel or multi-trolley arrangements are possible to suit most freezing schemes and schedules, thus enabling bakers and frozen-dough manufacturers to meet the expanding market potential for high quality frozen products at competitive prices. Mechanical blast-freezers with a multi-trolley loading facility provide flexibility, economic running costs, and the ability to handle all dough-piece shapes and sizes. Figs 155 and 156 provide an overview of the various temperature/time applications for dough-freezing, retarding/storing, preheating, recovery and proofing. Proofing schedules of retarder-proofers, can be usually varied between 0 and 30 hours, at variable heat and humidity. Average temperature ranges being 40 to 43°e, at 85% RH injected humidity. Brown-and-serve, or two-stage baking, which originated in the USA in the 1950s, represents another frozen-dough market sector. Products such as bread-rolls, croissants, baguettes, buns, Danish pastries, etc., are proofed, then baked at a sufficiently high temperature to give adequate crumb rigidity, but no crust colour. This is achieved by allowing the core temperature to reach 75-80o e for a duration of 10 to 15 minutes only. This operation can be either completed in a conventional oven at 135 to 147°e, or by utilizing a microwave oven. Bake-offfacUities provide small and medium-sized bakers with value-added sales potential, both for freshly baked products, and snack take-away products. This new market sector has been identified and exploited in continental Europe, both at manufacturing and retail shop level. Most bakery and confectionery retail shops now have a 'snack-corner', which serves fresh bake-off products, snacks, and savoury/salad-filled baked products, which can be consumed either with coffee at the 'snack-corner' bar, or packed for taking away. This facility is normally run alongside a high-class restaurant or tea-rooms with table-service, in addition to the baked product retail counter sales. In some countries, the bake-off facility is located on display in the shop, and in others adjacent to the shop within the production area. Where freezer capacity and production capability coexist, bake and freeze, and make and freeze and store, can all become complementary integrated operations. The existence of a bake-off 'show-bakery' (German Schaubiickerei) or in-store (German Kaujhallenbiickerei) gives the sales areas an active focal point of interest, and a freshly baked or 'home-baked' atmosphere. In the German-speaking countries where a bread-roll is no longer considered fresh after 4-5 hours of leaving the oven, owing to loss of crispness, a freeze-thaw-proof-bake cycle allows both industrial bakeries and in-store bake-offs to compete with the master-craftsman baker. Although, the master-craftsman baker also makes fuJI use of dough-freezing processes to plan production, and provide freshly baked products round the clock. Only the master• craftsman baker (Biickermeister) has the expertise to produce the quality required in this important bread-roll market, where the consumer is most discerning. In Bavaria and Austria, where the Kaisersemmel is the favourite partner for food and wine, these roJls have to be consumed within 2 hours of leaving the oven to be fresh. Therefore, production is organized on a continuous basis in smaJl 2-hourly batches. A freeze-store-thaw-proof and bake-off cycle permits supply to meet demand with a minimum of stress for the baker. 826 Handbook of breadmaking technology

In France the freeze and bake-off concept is applied within the bakery rather than being on show in the shop. In The Netherlands bake-off equipment is utilized by bakers as a general procedure to make their own products, often in outlets not attached to the main production bakery. Products usually also include a local specialty, in addition to the standard range of snacks. In Belgium bake-off equipment is to be found in the supermarkets, often located in an in-store bakery, sited in full view of the public. In the UK bake-off equipment for savoury products, e.g. pies, pasties, sausage-rolls, has been used in baker's shops for several decades, but its application by the baker for fermented products is a relatively recent innovation. The supermarket-chain in-store bakeries first applied the concept to fermented products in the UK. With the continuing growth of the bake-off concept, many frozen-dough companies have entered the market, often marketing bake-off equipment and the necessary advice and expertise. The multiple industrial bakery groups also operate in the market through frozen-dough company subsidiaries. Many innovative bakers with retail outlets now manufacture from scratch those items in great demand, and purchase in frozen dough form, items which are either uneconomic to produce, or which have only limited demand. In both cases the dough·pieces can be frozen and stored to provide an inventory of products to meet demand through subsequent thawing, proofing and bake-off.

Dough-Jreezing presents new technological problems, which demand considerable research in order to apply the appropriate solutions. On freezing, life processes in a product become suspended, and ice crystals form. Subsequent application of thawing temperatures, recovery temperature, then proofing temperatures, and finally baking temperatures, all result in changes in dough structure, and the colloidal behaviour of the individual dough components relative to the concentrations of free and bound water present. Structural stability of the gas cell-wall membranes, which form eventual crumb-porosity, during these changes in temperature and state, coupled with the ability of the yeast cells to live through such changes, and retain their vitality, are crucial to final product quality. Therefore, yeast stability and proofing-power after the hazards of freezing, are as important as the dough structural integrity itself. Wolt and D'Appolonia, have defined frozen-dough stability in practical terms as the 'ability of a thawed dough to proof in an acceptable period of time, and to bake into a loaf with normal volume and characteristics'. Wolt, M. J., and D'Appolonia, B. L. (1984) Cereal Chern., 61, p.209. Aspects of frozen-dough processing, which determine its stability will include product formulation, yeast genotype and properties, dough fermentation' period before freezing, duration and storage conditions, and freeze/thaw conditions. When freezing, it is important to achieve a core-temperature of -lye as rapidly as possible, average product temperature then being under -18°C. Owing to the presence of salt and sugars, and other soluble dough components, the dough does not begin to freeze at DoC, but instead within the range - 3 to - 8°C, depending on the concentration of soluble matter in the dough water (depression of the freezing-point). The pure water molecule will crystallize out, and the residual solution becomes more concentrated. With increasing concentration, its freezing-point is depressed, requiring progressively lower temperatures for the subsequent freezing process. The effective freezing-time is the sum of the 'pull-down'-time (ambient to zero), the solidification-time (0 to -lO°C), and the residual cooling-time. Within the solidification-time most of the free water becomes frozen. As an index of the correct freezing of a food, the 'effective-rate-of-freezing' is the accepted norm, expressed in cm h - 1, being the quotient of the shortest distance of the food surface from its centre (cm) and the effective freezing-time (hours). However, the 'nominal-rate-of-freezing' is more generally employed, which is the quotient of the shortest distance of the food surface from its centre (cm) and solidification-time (hours). According to Gutschmidt, the nominal-rate-of-freezing allows a classification of relative rates for food materials, as follows: under 0·2 em h -1 = very slow freeze; 0·2 to 0·9 em h -1 = slow freeze; I to 5 cm h - 1 = rapid freeze; and over 5 cm h - 1 = very rapid freeze. Notes and references 827

Gutschmidt, J. (1963) Tiefkiihl-Praxis, 4, 10, p.8. Fundamentals of freezing and the frozen storage of foods (German). The more rapid the freezing-rate, the less the damage the microstructure of the food undergoes. The formation of small, evenly distributed ice crystals prevails, and the sepa• ration of the liquid phase is therefore prevented. Thus, the nominal-rate-of-freezing must be at least 1 cm h - 1. This rate can normally be achieved with mechanical blast-freezers, and cryogenic spraying with liquid nitrogen results in freezing-rates of more than 15 cm h -1. However, in the case of baked-products the technological advantages are not reflected in the end-product quality. Frozen storage ojdough, which is carried out at - 18°C or below, must ensure that the optimal structural condition achieved by rapid freezing is maintained. Temperature fluctuations should be avoided, since they only encourage recrystallization. Recrystallization is the progressive diffusion of water-vapour from the small ice crystals to the larger ones. This process, which depends on the size of the crystals and the surface pressure which they exert, has the same net effect on the structure of the product as a slow freeze. Recrystallization increases with temperature, since the pressure difference of the water-vapour around the large and small crystals is greater. Also, the smallest ice crystals melt first with each temperature rise, which only increases the vapour pressure difference still further. According to Marston, once a solidly frozen layer of some 3-4 mm has been formed by rapid freezing of the outer shell of the dough-piece, and the core temperature has attained O°C, further freezing can take place in a storage-freezer maintained at - 20 to - 23°C. Excessive moisture loss is prevented, by packaging the dough-pieces in polyethylene bags and placing in corrugated cases prior to transfer to the storage-freezer. The storage-freezer temperature is maintained at -23·3°C. Marston, P. E. (1978) Bakers Digest, 52, 2, p. 18. Freezing-temperatures Jor bread doughs, amongst other dough-freezing variables, were studied at the American Institute of Baking by Lehmann and Dreese. They concluded that bread doughs have the most consistent quality bread when blast frozen at -21 to -29°C to a core temperature of -9 to -5°C. The inclusion of 62 D.E. corn syrup or a 42% high fructose corn syrup (HFCS) instead of sucrose, at the 8% and 10% levels, reduced final proof• times of frozen-dough stored at - 24-4°C for 26 weeks. Lehmann, T. A., and Dreese, P. (1981) Am.lnst. Baking Tech. Bull., 3, No.7. Stability offrozen dough-effects of freezing temperatures. Further work on frozen white bread dough by Dubois and Dreese at the same Institute, established that doughs containing corn syrup gave in general, lower-volumed bread than the other sweeteners employed. Dubois, D. K., and Dreese, P. (1984) Am. lnst. Baking Tech. Bull., 6, No.7. Frozen white bread dough-effects of sweetener type and level. Frozen-doughJermentation stability is the most important aspect of frozen-dough technology. The final dough, when thawed must respond to proofing temperatures within an acceptable time, and bake-out to a product of normal volume and characteristics. In studies concerning the effects of the length of dough fermentation and conditions of freezing on gluten properties, and quality of the finished products, Teshitel, at the Technological Institute of Odessa, USSR, made the following significant observations. Bread dough fermented with yeast for periods not exceeding 2 hours, and then held in frozen storage at - 12°C, or - 18°C for 4 weeks, resulted in increases in the amount of gluten in the dough during storage for 2 weeks at -18°C, but showed a slight decrease at -12°C during that period. Dough rheological properties and hydration changes appeared similar at both storage temperatures, but were less expressed at - 12°C. Teshitel, O. V. (1987) Klebopek. Konditer. Prom-st, 8, p. 23-4 (Russian). There is considerable research evidence to confirm that fermentation before freezing reduces yeast viability. Sugihara, T. F., and Kline, L. (1968) Bakers Digest, 42, 5, p.51. 828 Handbook of breadmaking technology

Merritt considers that dough fermentation before freezing has more effect on dough stability, and the proofing-time required, than any other single variable. The stability of frozen dough is inversely related to the amount of fermentation before freezing. Fermentation times before freezing of not more than 1 hour gave dough stability of a few weeks only; 30 minutes gave 3-4 months; and zero time gave about 12 months. Merritt's tests refer to a: dough containing: flour 100 parts, water 65, dry yeast 4, bromated yeast-food 0·5, salt 1·75, dextrose 7·0, shortening 9·0, sweet-whey 5·0, mixed at high-speed with a refrigeration jacket, mixing to full development to give a final dough temperature of 18 to 21°e, allowing 10-15minutes for fermentation during make-up. Freezing was at air temperature - 32°e, and frozen storage at below -12°e until required. This dough could be stored for 1 year, 16-20-ounce slabs showing good proof after 16 months storage. On removal from the freezer, proofing was at 35°e and 80% RH, baking at 218°e for 17minutes. Merritt, P. P. (1960) Bakers Digest, 34, 4, p.57. Merritt attributes the greater yeast stability in unfermented frozen doughs to its dormant state at the mixing stage.

Yeast managementfor frozen-dough preparation can present problems. Both compressed- and dry-yeasts are satisfactory for doughs to be frozen. Recommended amounts, based on flour weight, are 6-10% for compressed, and 3-5% for active dry-yeast, depending on the desired speed of final-proof. Where active dry-yeast is used, it must be free of significant amounts of dead cell material, which weakens the dough. Only fresh yeast should be used, and storage fluctuations avoided. Dead cells can be identified by staining a cell suspension 1: 1 with an equal volume of methylene blue 200mg, potassium dihydrogen phosphate 27·2g, and disodium hydrogen phosphate 0·07 gJlitre distilled water. Dead cells stain red, allowing counting under a microscope. Hsu and co-workers also observed that the quality of the yeast greatly affected frozen dough stability. Finding those with protein contents in excess of 57% performing best. Hsu, K. H., Hoseney, R. c., and Seib, P. A. (1979) Cereal Chern., 56, p.419. Wolt and D'Appolonia found that fresh compressed yeast performed slightly better than either active dry-yeast or instant-active dry-yeast over a storage period of 20 weeks. Wolt, M. J., and D'Appolonia, B. L. (1984) Cereal Chern., 61, p.213. Bruinsma and Giesenschlag conducted tests to establish the effects of 12 weeks' frozen• storage, with daily freeze/thaw cycles on the viability of dry-yeast and compressed-yeast. They found that higher levels of active dry-yeast gave consistently shorter final proof-times than compressed-yeast. Proof-times and gas-production showed little change over seven consecutive freeze/thaw cycles for either type of yeast, but crumb structure became rapidly devalued over the seven cycles; the dough became progressively weaker and friable, making handling difficult. Bruinsma, B. L., and Giesenschlag, J. (1984) Bakers Digest, 58, 6, p.6. Mazur and Miller found that the freezing-rate had a profound effect on the survival rate of yeast cells. Rapid freezing to - 30 0 e and below, reducing the cell survival rate to less than 0·01 %; whereas slow cooling to the same temperature results in up to 65% remaining viable. Mazur, P., and Miller, R. H. (1967) Cryobiology, 3, p.365. Yeast cell destruction by rapid cooling is due to the formation of intracellular ice crystals which destroy the structure of the cell protoplasm. Slower cooling rates allow the yeast cells to transfer sufficient intracellular water to the outside, thus preventing ice crystal formation inside the cells. Freezing at excessively low temperatures also diminishes yeast viability. In dough, yeast cells freeze at about -35°e, and are unable to reproduce much below -12°C. Hsu and co-workers established proof-times of 72 and 132 minutes for doughs frozen at -woe and -40oe respectively. Doughs taken down to -78°e show only minimal activity on thawing. Hsu, K. H., Hoseney, R. c., and Seib, P. A. (1979) Cereal Chern., 56, p.424. Lorenz has suggested that freezing the dough slowly down to _lOoe only, followed by rapid defrosting, results in improved frozen dough stability. Notes and references 829

Lorenz, K. (1974) Bakers Digest, 48, 2, p. 14. However, it must be acknowledged that many of these suggestions are contrary to current practice. In order to seek solutions to such problems it is essential to consider the basic requirements of yeast, as a microorganism, for life and growth. In the vegetative (reproductive) state, the yeast cell contains 85% water, since for the processes of nutrient uptake, transport of the metabolites, water is essential. When this water is removed, metabolism ceases together with growth and reproduction. Most vegetative cells die as a result of drying-out, but spores can survive considerable drying-out. However, yeast cell development depends less on the absolute moisture content of the substrate (dough) than on the content of ,available' or 'active-water'. The unit of measurement of the available water of a substrate is referred to as its 'water-activity' (aw ), which is expressed as the ratio of the vapour pressure of the substrate, i.e. its surrounding atmosphere (p), and the saturated vapour pressure of pure water (Po) at the same temperature, i.e. aw = p/Po. Pure water has an aw value of 1·000 but with increasing content of dissolved particles, this falls to aw values below 1. Each soluble particle has an envelope of water molecules surrounding it, which are no longer available to the yeast. A completely water-free substrate having an aw value O. Most microorganisms can only develop in substrates with aw values within the range 0·85 to about 1·00, but Some specialized ones can grow at 0·62. Most species of yeast have a minimum aw value for growth between 0·88 and 0·91. Burcik, E. (1950) Arch. Mikrobiol., 15, p.203-35. Concerning the relationship between the hydration-state and growth of bacteria and yeasts (German). The resistance of microorganisms to cold depends on the chemical composition of the substrate (dough) within which they are subjected to low temperatures. Resistance against cold increases with increasing concentrations of soluble solids. Anions and cations also have an influence on resistance to cold; also unfavourable pH conditions lower their resistance. The presence of colloids generally, and protein and lipids exert a protective influence against the cold. Protective colloids like gelatine, which are hydrophilic (water-binding), considerably reduce the death rate due to cold of yeasts and bacteria during freezing. Bound water cannot be easily frozen, therefore no ice crystal formation can take place. In general, high moisture contents result in the death of considerable numbers of yeast cells, whereas lower levels offer better protection against the cold, hence the general use of freeze-drying (lyophilization) for long-term storage of culture collections of microorganisms. Yeast cells maintained in the stationary reproductive phase remain much more resistant to cold than those in the vegetative phase. Spores in particular showing greater resistance. Rapid freezing of cells with adequate bound water is better tolerated than slow freezing, which is also true for thawing. The critical temperature range for the cell liquid is freezing temperature range - 4 to -10°C, and repeated freeze/thaw cycles results in a cumulative loss ofliving cells. Mechanical damage as a result of the volume increase due to ice formation is not the only problem. During freezing, the water component of the solubles is first frozen, resulting in a concentration of the dissolved solids. This results in an osmotic pressure increase, changes in pH, and a concentration of mineral salts, which causes irreversible damage to the physical and chemical properties of the colloidal structure of the cell protoplasm. Such changes also give rise to toxicity, resulting from concentration at freezing, thus inhibiting cell function. Damage to the cytoplasmic membrane results in a disturbance of the metabolic equilibrium, and irreplaceable loss of energy. Prolonged storage of yeasted doughs in the frozen state results in progressive loss ofliving cells, owing to free-radical formation. Microorganisms generally are best protected from freezing damage by freezing with liquid nitrogen at about -196°C, in this way, their biochemical properties remain unchanged for years. Stevenson, K. E., and Graumlich, T. R. (1978) Adv. Appl. Microbiol., 23, p. 203-17. Injury and recovery of yeasts and moulds. Farrell, J., and Rose, A. H. (1965) Adv. Appl. Microbiol., 7, p.335-78. Farrell, J., and Rose, A. H. (1967) Ann. Rev. Microbiol., 21, p.101-20. Proceedings of low-temperature microbiology symposium 1961, Camden, New Jersey. Campbell Soup Co., 1962. Collective authorship. 830 Handbook of breadmaking technology

Precht, H., et al. (1973) Temperature and Life, Springer-Verlag, Berlin, Heidelberg, New York. Unless new yeast strains are developed with higher tolerance to prolonged low temperature storage in dough products, the only option is to modify the formulation, processing, and freeze/thaw procedures to protect the viability of the yeast cells enough to result in an acceptable final proof-time, and crumb porosity. Frozen-dough production procedures currently involve the preparation of a rather stiff straight dough on a no-time schedule, using 4-6% yeast, shortening about 5%, sugar 5%, and non-fat dry milk at 4% (as necessary), all based on flour weight. The dough should be well developed and homogeneous, mixing temperature being kept at about 22°e, by chilling if necessary. The dough can then either be transferred immediately to make-up, as suggested by Rosenholtz and Boyd. Rosenholtz, S. (1985) Proc. Am. Soc. Bakery Engrs, p.141. Boyd, W. E. (1985) Proc. Am. Soc. Bakery Engrs, p.38. or given a maximum 15-minute relaxation-time to render more workable. Where the strict no-time schedule is utilized, the rounded dough-pieces are given an intermediate proof of about 5 minutes to relax. Flour quality should be above average, with gluten elasticity and resilience. A patent flour, milled from medium-strength spring/winter wheat grists, with added bromate or ascorbic acid is suggested, gluten quality rather than quantity being the criterion. A good water absorption starting level being 60%, instead of the normal 64% for a conventional dough. Dough salt levels should be 1,5-2,0% flour weight. The moulded and shaped dough-pieces are then deposited on trays, and loaded on racks or conveyors and either placed in a blast-freezer for the required time, or slowly passed through a freezing-chamber or tunnel. Primary freezer area temperature should be maintained at -29 to -40oe, being exposed to air currents of 600 ft/min during transit. Doughs are best covered with polyethylene film or bags during freeZing to prevent surface moisture loss and crusting. A liquid nitrogen flash or jet stream is the most rapid freeze rate in use, taking an average of 6 minutes. A blast-freezer of the staionary design will take about 2-3 hours to reach a core temperature of -12°e in the case of a 2-lb loaf. Packaging will add about 30min/unit to freezing-times, depending on unit mass. In the USA, R. Bamford of the American Society of Bakery Engineers has suggested the conditions shown in Table 74 for blast-freezing with a standardized air flow of 600 ft/min. During the freezing of all the listed products, the air temperature was maintained at - 36°C. Thompson, D. R. (1976) Bakers Digest, 50, 2, p. 28, recommends blast-freezing at temperatures of -35 to -40oe, using air velocities of 600 to 700ft3/min, and for such time that the core temperature of the product reaches -18°C. Further stipulations are that the holding-freezer units should be maintained at air temperatures between - 23 and - 29°e, not allowing it to rise above -18°e at any time. Furthermore, the air should be held at the highest RH possible in practice, and freely circulating. Under these strict conditions, product quality could be preserved for several weeks or months. Many producers use a temperature of -23°e, although -18°C is often quoted as satisfactory after rapid cryogenic-freezing; this provides an insurance against mistakes and temperature fluctuations. Cryogenic freezing-rates are 10 to 30 times faster than any blast-freezer, and a 70-ft belt conveyor will freeze up to 5000 lb/hour in a countercurrent tunnel system. Liquid nitrogen being introduced into the freezing zone by atomized spray headers at a controlled rate. The low temperature gas circulating at speeds of up to 7000 ft/min zonally. Entry zones effect a precool of the product to -18°C. The actual freezing zone freezes at -196°C, with a tempering final zone prior to exit of -108°C. A significantly better retention of product quality, compared with a mechanical freezer is obtained. Equipment simplicity in design, lower initial and subsequent maintenance costs, lower energy costs, and less floor-space are other attractions. Where space is limited, and capacities of around 10000lb/hour are involved, spiral cryogenic freezers offer the best solution. Thawing conditions are important, and represent a long, frustrating step, unless integrated into the production planning on a programmed basis. On removal from the holding-freezers, Notes and references 831

the core temperature of the products is -18 to - 21°C. In order to avoid too great a temperature gradient between the core temperature and the dough surface temperature, the products are placed in a defroster to thaw gradually. According to R. Bamford of the American Society of Bakery Engineers (1975), the optimal defroster temperature is 37 to 49°C, at RH 50% to 60%, using an air velocity of 200 to 500 ft/min. However, initially, air flow rates of 150 to 200ft3/min 150 to 200ft3/min are required to raise the product temperature from -18°C up to 21°C. The time required to reach a core temperature of 21°C will depend on the size, type and packaging of the product. Table 75 provides some examples of thaw-times from -18°C up to 21°C. Potassium bromate when supplemented with ascorbic acid results in a proof-time reduction of 23 minutes, after a 2-month frozen-dough storage period. Varriano-Marston, E. et al. (1980) Bakers Digest, 54, 1, p. 32. Oxidant type and amount will depend on local regulations, and processing conditions. Both ascorbic acid and potassium bromate improve frozen-dough stability, either used alone or in combination. The level of treatment will depend on flour quality and response, and the inverse relationship between oxidant level and dough mixing temperature. Lower dough temperatures require more oxidation to optimize response to final-proof. Bromated yeast foods can be added at the 0·5% level. Sugars are used at the 5% to 10% level, based on flour weight, in rich formulations, but in the case ofleaner bread doughs 5% to 6% is adequate. Sucrose or dextrose give similar results, or maltodextrin can be used to reduce calorific values. Shortenings are included in the form of good quality lard, or vegetable shortening based on palm-kernel oil, at the 5% flour weight level, depending on the formulation. Mono-/diglyceride-type emulsifiers added at about 3% of shortening weight improves product volume and crumb quality. The distilled 90% monoglyceride is the most active source on a weight-for-weight basis. Datem, or diacetyl tartaric esters ofmono glycerides, owing to their protein complexing, make the dough more tolerant and gas-retaining; but the yeast vitality must be also present at final• proof. Ethoxylated derivatives of mono- and diglycerides (EOM) also improve dough rheology, but requires yeast vitality at final-proof. Sodium stearoyl-2-lactylate (SSL) strengthens the dough, producing a greater oven-spring and improved crumb grain; but yeast vitality is a prerequisite for final-proof. Dubois, D. K., and Blockcolsky, D. (1986) Am. Inst. Baking Tech. Bull., 8, No.4. Frozen bread dough-effect of additives. Surfactant functionality depends on hydrophilic/hydrophobic balance. According to ionic activity, surfactants can be divided into three groups. Anionically active ones are water• soluble, and become ionic ally dissociated, e.g. calcium or sodium stearoyl-2-lactylates (CSL and SSL); non-ionic ones, which do not dissociate into ions, e.g. mono- and diglycerides of fatty acids, and sugar alcohol esters of fatty acids (sorbitol monoesters, and the 'fat-sugars' such as sucrose and glucose esters), also their polyoxyethylene derivatives; ampholytic or dipolar ones with mixed ionic functionality, e.g. the phosphatides of which the lecithins form a group of allied compounds. The phosphoryl-choline moiety functioning as a dipolar, or 'zwitterion'. Frozen-dough formulation in certain cases, can utilize the functionality of sucroglycerides, especially those based on palm oil. Formulations containing sugars, shortening and eggs benefit in particular from their inclusion at the 2-3% flour weight level. The functionality of the sucroglycerides derived from palm-nut oil, containing palmitic acid 47·5%, oleic acid 40·0%, linoleic acid 7·5%, stearic acid 4·0%, and myristic acid 1·0%, are particularly effective. 832 Handbook of breadmaking technology

Hydrocolloids also show good frozen dough functionality. Their precise function is to stabilize water movement within the dough during freezing, when it is being subjected to a number of freeze/thaw cycles. Locust bean (carob), and guar gum, both prevent excessive ice crystal formation during freezing, the active component in both cases being the galactomannans, derived from the seed endosperms. Both gums produce high viscosities at low concentration, therefore, only concentrations of up to 0·1 % flour weight are normally included. Karaya gum, used at 0·1 % flour weight, often exerts a hydrocolloidal synergistic effect when used with monoglycerides at about 0·3% flour weight in doughs. The rheology of the polysaccharide gums can be adjusted to provide either extensible or short-textured gels as appropriate. Native and modified starches also exert good freeze/thaw tolerance properties in frozen-dough products, preventing moisture movement within the dough system. Waxy sorghum starch has a relatively low moisture release over about three freeze/thaw cycles; cross-linked amylopectin starches yield mono- and distarch phosphates, on phosphorylation, which are freeze/thaw stable. Oxidatively modified maize (corn) starch, producted by treating the starch with 0·05-0·07% potassium bromate prior to drying at 160°C, improves dough stability, fermentation response, and product porosity. Native starches, which give long, cohesive• textured gels are: tapioca, potato and amioca. Pregelatinized potato starch also provides cold-swelling, and is stable at low temperatures. Dough base and conditioner manufacturers also market composites for addition to frozen• doughs, providing longer frozen storage life, and improved recovery. Many of these products include the functional components already discussed. Frozen-doughformulations based on the Reddi-Sponge Process (R. G. Henika) patented by Foremost Foods, Dublin, California, USA, allow a doubling of the frozen storage shelf-life, and permits the use of lower dough temperatures, e.g. 18 to 21°C. The application of direct biochemical action on the flour proteins prolongs dough storage potential. Typical dough formulations contain: yeast 4·0%, yeast-food 0·5%, salt 2·0%, shortening 3·0%, mono/• diglyceride emulsifier 0·4%, Reddi-sponge 3·0%, using total oxidant level 70-80 ppm, with added sugar up to 8 %, all based on flour weight 100 parts. Doughs should be mixed to full development at low and high speeds, and if the mixing-time exceeds 12 minutes, it is better to withhold the yeast and add over the last 4-5 minutes of mixing for subsequent batches. Mixer-jacket temperature should be adjusted to aim at dough temperatures between 21 and 24°C. The dough is allowed a lO-minute relaxation period, after which it is divided, rounded, and given a minimum intermediate-proof before shaping. The dough-pieces are then blast• frozen at - 24°C or lower. The sequence in which the dough ingredients are added during mixing has a significant effect on final proof-time and yeast activity. Doughs held at retardation temperatures for up to 24 hours before proofing, show reduced (shortened) final• proof times, and improved product volume, although other quality criteria may not show an improvement. These trends were also confirmed by Dubois and Blockcolsky at the American Institute of Baking, Manhatten, Kansas, USA. Dubois, D. K., and Blockcolsky, D. (1986) Am. [nst. Baking Tech. Bulletin, 8, No.6. Amyloglucosidase supplementation is more effective in increasing loaf volume in lean sugar• free doughs than fungal alpha-amylases, and is a useful ingredient for frozen-dough work. Limit-dextrinase, present in fungal enzymes, is capable of hydrolysing starch or dextrins to glucose. This enzyme was shown by Pomeranz to belong to a group of amyloglucosidases which specifically hydrolyse starch or dextrins to glucose; earlier work by Pomeranz and co• workers, using combinations of alpha-amylase and amyloglucosidase from fungal sources, confirmed that the improving effect of amyloglucosidase depends on the sugar level in the formulation. Leaner low-sugar doughs require higher levels of added amyloglucosidase to yield loaf volumes comparable to doughs with higher sugar and lower levels of enzyme. Pomeranz, Y., and Finney, K. F. (1975) Bakers Digest, 49, p.20. Pomeranz, Y., Rubenthaler, G. L., and Finney, K. F. (1964) Food Technol., 18, p. 138. Noles and references 833

These workers established that at higher dosage levels, amyloglucosidase was more effective than fungal alpha-amylase in sugar-free doughs for the purpose of increasing loaf volume. For a frozen-dough baguette formula: flour (protein 12% dry matter, gluten minimum 25%) 100 parts, compressed-yeast 6, ascorbic acid 50-70 ppm, amyloglucosidase preparation added at optimal concentration (determined by baking-tests), salt 2'0 (added at final mixing• stage), water adjusted to flour absorption. Frozen-dough procedure, as a guideline to the freeze-store-thaw-proof sequence, should be carried out as follows. Use a rapid freeze to a low temperature to minimize ice crystal size utilizing a blast-freezer technique. A liquid nitrogen flash, or jet streams, offer the fastest and best procedure (average freeze-time 6 minutes), otherwise a mechanical blast system is preferred. Doughs are ideally covered with polyethylene film or bags during freezing to prevent moisture loss and skinning. A blast-freezer will reduce the core-temperature of products to - 20°C within about 30 minutes; a large 16-rack roll-in unit freezing a rack of rolls within 20 minutes to - 20°C from ambient. Freeze-storage is maintained at - 20 or - 23°C to allow a safety margin against temperature fluctuations, being part of a cold-store complex, with attached recovery room for controlled thaw-out of products (humidity, air• flow, and temperature). A slow recovery/thaw-out system is placed under automatic control, preheating from sub-zero temperatures up to about 3°e. This can be varied in duration to meet requirements, maintaining humidity at 70-75%. The actual recovery phase takes place between 3°C and about 24°C at 70-75% RH. The final-proof phase ranges from 24°C to 43°C, with RH maintained at 85%. In the absence of a cold-store recovery complex, thawing is best carried out in a warm draught-free location at 27 to°C to 29°C, ideally within an enclosure at RH 60-70%. If carried out in the open bakery, the products must be covered to prevent moisture loss and skinning. Final-proof is then completed at 30 to 45°C, depending on the product.

3.6.4 Bread Preservation by Freezing Preservation of bread and baked products by freezing technology has been applied in the USA and Europe for several decades. Although many refinements in technology and equipment have taken place over the past two decades, the choice of temperature ranges for the retardation of staling of baked products falls between - 20 and -190°e. The most unfavourable range is + 50 to - 7°e. For successful application, the products must be frozen within 4 to 8 hours of leaving the oven. Freezing can take place either with or without packaging, or with a double-layer of wrapping material. Although packaging prior to freezing reduces the freezing-rate to reach a loaf centre-temperature (core) of - 30°C-the time required being about twice as long under identical conditions-the wrapped products remain fresh two to three times longer, owing to improved moisture retention. The choice of wrapping material often depends on the product, but polyethylene films remain the popular choice on economic grounds. Cathcart and co-workers, in commercial freezers, found that bread remained fresh in flavour and aroma for up to 30 days when held at - 35°C, and in a saleable condition for up to 345 days, the limiting factor being the ultimate development of an off-flavour. Cathcart, W. H. (1941) Cereal Chern., 18, p.771. Cathcart, W. H., and Luber, S. V. (1939) lnd. Eng. Chern., 31, p.362. Baked products are normally frozen by using a forced air current. Air speeds of 2 to 4 m/s are found optimal to reach air-temperatures of - 25 to 3S°e. This air speed provides a heat• transfer coefficient of 18 to 24 W m - 2 K - 1. Any increase in air speed above this 2 to 4 m/s level, will progressively reduce the heat-transfer coefficient. This is due to the relatively poor thermal conductivity of baked products generally, although the air-cells in products with increasing shortening contents are correspondingly fewer. Pre-frozen quality levels of products can only be maintained, when utilizing the freezing process to retard staling and physical changes, by rapid freezing, which means passing 834 Handbook of breadmaking technology through the unfavourable temperature zone of + 50 to - re as rapidly as possible. The limiting factor here is air speed v. the heat-transfer coefficient from the products. As a guideline, a 1-kg loaf cooled down to 20°C after baking should not require longer than 4 to 5 hours to reach a core temperature of -18°C. The time taken to attain a specific core temperature will depend on product mass, under any specified conditions of blast-freezing. By moving very cold air across products at high velocity, fast-freezing is achieved without the formation oflarge ice crystals, which damage texture, and leave a dry end product, depending on their water content and water-binding capacity. This is particularly important when freezing doughs. Unwrapped bread and baked products, when frozen, show excessive drying out within 1 to 2 weeks, owing to the lower RH, in storage freezers. Freezer storage-temperature has a significant effect on the staling rate. Bread held within the range - 10 to - 7°C, which corresponds to its freezing-range, will show considerable crumb• firming, and flavour loss within a period of 1 week. At a storage temperature of -18°C, crumb-softness will remain relatively stable and constant for about 1 month. However, prolonged storage at - 18°C results in a progressive devaluation of bread quality. Even if the temperature is allowed to rise to -l2oe, only just outside the freezing range, crumb-firming becomes apparent within a few days. Temperature fluctuations above -7°C result in moisture migration within the crumb of the frozen bread. Temperatures around -10°C even give rise to sublimation of the ice crystals after about two weeks' storage, which can be identified as white rings forming in the crumb layers immediately under the crust. This is indicative of crumb drying beneath the crust, moisture having been transferred by sublimation and diffusion from the high-moisture crumb-centre to the relatively low• moisture crust-zone. Blast-Jreezing or 'shock-freezing' is the most efficient method of bread and baked product preservation, whether in the form of a high-velocity, very cold air movement around the product, or by the use of a liquid cryogenic, e.g. nitrogen or carbon dioxide. This procedure avoids any subsequent separation of the crust from the crumb, which is brought about by a moisture redistribution within the layers under the crust, the internal layers losing moisture to the outer layers resulting in a separation of crust from crumb. Bread staling processes proceed most rapidly within the temperature range + 60°C and - 2°C; hence the importance of a blast-freezing system to preserve freshly baked quality. On a batch freezing basis, this is achieved with a trolley-loading blast-freezer, coupled with a low-temperature holding cold• room. This provides a good output/time ratio. Tunnel blast-freezing is, however, a more rational operation, the products being passed through a tunnel on a band conveyor, within which a very cold forced-air flow prevails. Heat-transfer takes place by convection, according to Newton's law, the temperature gradient becoming less as the freezing-time increases. The value of the heat-transfer coefficient depending on the air speed within the tunnel, which is optimally set at about 2-4 m/s. If this range is exceeded, its influence on heat-transfer steadily decreases. Average tunnel temperatures are within the range - 25 to - 35°C. In the USA, blast-freezing is also used for bread products, using standard air-flow rates of 600 ft/min, reaching final temperatures of -20 to -30°C for fermented goods. Freezing-time depends on the type and extent of the packaging material used. Table 76 shows relative times required for products to reach - 12°C in hours. A 2-lb unwrapped loaf of bread would require 3·0 hours, a single-wrapped loaf 3·5 hours, and a double-wrapped loaf 4·0 hours to reach -l2oe at the centre (core), at the standard 600 ft/min air-flow. In the case of the blast-freezing of baked bread-rolls, the temperature/time sequence is as follows: -rolls cooled from 98°C to 35°C, taking about 30 minutes; -rolls cooled from 35°C down to about - 10°C over a period of about 50 minutes, in the first zone of the blast-freezer tunnel; -rolls further cooled down from - 10°C to - 20°C over a further 30 minutes, in the second zone of the blast-freezer tunnel; Notes and references 835

-freeze-store at -18°C to - 21°C for about 2-3 days in freeze-store rooms; -thawing from -18°C to -21°C, up to ambient temperature, 20°C plus, requiring about 65 minutes. See Figs 157 and 158. Freezing applications for baked products can be divided into: (I) Chilled storage, intended for short-time preservation only, using temperatures of 0 to +4°C, e.g. chill-cabinets with residence-times limited to days. This will inhibit the growth of moulds and liquifying bacteria, e.g. B. subtilis, to a degree. In such cases, fermented products, baked-pastries, and pastry-dough intended for domestic bake• off, gateaux, desserts, and meat pasties should be suitably wrapped. Permissible residence-times of products will depend on whether they are wrapped, on their type and on·their formulation, and on whether the cabinet is open or closed. Recent draft food hygiene regulations in the UK stipulate, for same-day sale, that sandwiches be stored at a maximum of 8°C, and cream cakes at a maximum of 5°C. (2) Longer-term preservation, extending to weeks or months, with adequate packaging or sterilization before packaging, can be carried out in closed cabinets set at -18°C. Longer-term preservation by freezing is intended for setting up a production-inventory programme, aimed at rationalizing and better coping with peak-demand periods. Table 77 shows the various phases, equipment and technological parameters involved in the preservation by freezing of bread-rolls and bread. Figure 157 shows the technological system for the freeze-preservation and thawing of bread and bread-rolls. Preservation of baked product freshness is best achieved during transit by dispatching in the frozen state and allowing to thaw, either during transit, or at the point of sale, in the case of relatively short distribution chains. For longer distribution chains, and where many wholesale and retail outlets have to be supplied, insulated freezer-vans or containers must be utilized. Industrial bakeries or frozen-food chains specializing in bakery products, with throughputs of 1000 kg/hour, utilize a direct contact refrigerant, known as a 'cryogenic'. Direct contact of the cryogenic in the gaseous state with the product provides very rapid freezing rates. Cryogenic systems use either liquid nitrogen or liquid carbon dioxide. Since the boiling point of liquid nitrogen is -196°C, a cryogenic system allows the application of very much lower temperatures than the air blast-freezer. Average tunnel lengths are 12 m with widths of about 1·8 m, the products passing under liquid nitrogen spray, which evaporates on contact; fans move the cold evaporated gas in a countercurrent direction, equilibrium at -18°C being achieved by retaining the product in the tunnel. Coolant cost on a continuous basis must be justified by a 24-hour production output. Advantages are the relatively small floor-space required, low maintenance, improved product quality, and flexibility. Partially baked or 'BrOll'n-n-serue' products are preformed and pre baked to the final size and shape, requiring only crust browning and fresh flavour development in a domestic oven. This concept is applied to rolls, breads and pastries, the aim being to bake the product to a point of maximum rigidity and volume, without actual crust formation. This is achieved by reducing the oven temperature to the range 120 to 150°C. Proof has to be controlled so that the oven• spring which takes place at the lower temperature is maintained within limits. Dough water absorption must be reduced to give a stiff dough, which will remain rigid on removal from the oven. Formulation modifications require straight doughs to be set at 32°C to 35°C, and sponge-doughs at the usual lower temperatures. Levels of yeast and yeast-food must be moderately reduced to contain oven-spring. Enriched formulations perform best for eating quality, and final-proof should be rapid at 38-40°C. Baking between 120cC and 150°C is maintained for as long as possible without crust browning, usually for about 10 to 15 minutes at a solid 140 c C. The product core-temperature must reach 82°C to avoid shrinkage or 836 Handbook of breadmaking technology

collapse on cooling. Product cooling and packaging must be carried out under sterile conditions to avoid mould infection, or product damage. Market trends, projected into the 1990s, indicate a growth market for frozen foods generally, with bakery products representing about 48%, being only second to ready-meals as the fastest growth sector. Where meat and dairy raw materials are utilized, the baking industry must adhere to safe storage-temperatures and handling procedures to avoid microbiological hazards, and the adverse publicity resulting from 'health-scares'. In the bakery frozen product sector there is also considerable scope for new product innovation and growth, wherever a convenience aspect can be introduced. Socio-economic trends show that the number of 1- to 2-person households is on the increase, that the population average age is increasing, and that the consumer has more leisure time at his or her disposal. Fast-food consumption has shown dramatic increases, and bake-off concepts are part of this trend. Product variety, and their health and nutritional attributes are now in the limelight. The large supermarket chains have taken the lead in publishing brochures and applying nutritional-labelling to the various types of food. The nutritional significance of salt, fats and fibre in the diet, the energy contribution to the diet of a given weight, and the contribution to the recommended daily amounts (RDAs) of each nutrient, have all been included in consumer information. For the baking industry, the success of the frozen product sector, whether in the form of dough or baked products, is due to greater flexibility in production, and the sale of fresh products round the clock. The 'bake-off' concept, according to consumer demand has proved to be a valuable technical innovation allowing the baker to plan production, and better cope with the peaks and troughs of demand. The demand for 'oven-fresh' products is also a growth market, especially the bread-roll and specialty- or variety-bread sector. The health and nutritional factor has resulted in the development of more interesting specialty products with added value for the consumer. These products are already showing steady sales increases and are expected to take part of the conventional white panned-bread market, which has hitherto commanded 70% of total bread sales in the UK. The secret of sales expansion in the baking industry is innovation, and the production of a wide range offreshly baked products. In-shop baking and product promotion, including special offers and features from other countries, resulting from recipe exchanges, will stimulate demand into the 1990s and beyond. Index

A2-ChTB/M, 422 Ascorbic acid, 31-4, 36,42,66,85,230 A-2 ChTT, 445 L-Ascorbic acid, 78, 235, 236, 320-1 1\ 12 assembly 120, 124 Aspergillus Acceletron, 565 awamori, 173, 234 Accurist dough divider, 436 candidus, 326 Acetic acid, 59, 66, 73, 103, 342, 343-4, niger, 30 347, 350-1, 484-5, 505 oryzae, 30, 234 Activated dough development process species, 390 (ADD), 25, 27, 231-233, 235, 490 Associated British Foods, 236 Active dry yeast, 467 Atlas Equipment, 400, 718 Aerobacter species, 326, 388 Auerman, L., 52,161,162,169,179,181, cloaceae, 326 190, 191,313, 573, 648, 674 Aflatoxins, 389, 390-392 Auerman et al., 158,225,643, 645 Agatova and Proskurjakov, 66 Australia, 27, 36, 72 Agene, 182,216,222 Austria: bread-making in, 94-5 Albumins, 3, 68, 73 Autoclave cookers, 55 Alcohol, 479, 480 AWB-100, 180 Allied Bakeries, 244, 248, 250, 253 Axford, D. W. E., 66 Allied Mills, 237, 242, 249, 257 AZCh oven, 167 Alpha-amylase, 30, 54, 235 Azodicarbonamide, 29, 33, 34, 66, 230, Amadori rearrangement, 588, 589 231,233,268 America. See United States of America American Machine and Foundry Company, 281, 431 Bacillus cereus, 382, 383 Amflow units, 28, 236, 280-283, 285, 443, Bacillus mesentericus, 389, 683, 711 490 Bacillus subtitils, 30, 389, 683, 711 Amino acids 51, 53, 61, 63, 64, 68, 75, 76, Bacto-Wort Agar, 354 78, 482, 483, see also under BAG-20, 167 individual names Baker et al., 21-2 Ammonium hydroxide, 234 Baker-Perkins-Invarsson system, 226 Amylase, 55, 84, 234 Baker-Perkins Amylograph paste viscosity, 58, 59 mixers, 182,207,224,261,262,430 Amylopectin, 38, 82 ovens, 211-13, 215, 600 Amylose, 38, 40, 82 see also APV-Baker Anger et al., 80 Baker's percent, 48 Aniline, 335 Baking AP-4/1, 308, 313 aims, 539-52 AP-4/2, 308, 313 aroma components, 590-5 APV-Baker, 262, 264, 265, 266, 420, 436, caramelization, 583, 584, 588 see also Baker-Perkins elements, 553-95 Arabinoxylan, 80, 83 flavour components, 590-5 Arkady Company, 236, 241, 250 heat- transfer, 560-8 Armenia, 483 humidity, 544, 558, 568-77 Artofex mixer, 93, 261,411,417 loss, 601 837 838 Index

Baking~contd. Brabender Maturograph, 40-1 moisture and, 555, 564, 573, 579 Bran-bread, 534-5 optimization of, 543 Bread requirements, 539-22 ageing, 656-76 starch and, 580-4 air temperature and, 646-7 steam, 544-7, 558, 569, 570, 575 aroma components, 656 temperature, 548, 550-2, 553-60, 559-60, cooling, 213-14, 638, 639-41; 568, 570, 572, 573, 579 moisture, 641-9, 656 times, 548, 569, 578-9, 583 freezing, 679, 708-tO, 711, 712 weight loss, 548 humidity and, 647 see also Ovens microbial infection, prevention of, 682-9 Baking tests, 327-35 mould and, 653-4 Baltimore Biological Laboratories, 379 nutritional value, 245-7 Barber, S., 91 packaging, 656, 680-2, 688 Barber et al., 348 pasteurization, 684-9 Barms,493 refreshing, 657, 665, 667 Barnes and Blakeney, 316 slicing, 213, 214, 235, 655 Barret and Joiner, 233 staling, 656-78 Bath processing, 37 retardation, 40, 679-82 Bean-flour, 88 storage, 649-78 Belova, L. D., 187 flavour changes, 676-8 Belova et al., 469 moisture and, 655, 662 Benzoyl peroxide, 42, 43, 216 temperature gradient, 676 Berliner, Dr, 313, 317, 318 wrapping, 213, 214, 681 Berliner and Koopman, 52, 80 British Arkady Co. Ltd, 42 Berliner short-sour process, 333, 345, 346, British Bakeries, 248, 249, 253 533 British Baking Industries Research Berlin short-sour, 106, 507 Association, 225, 227 Beta-amylase, 54, 174 British Cellophane, 214 Bezenchukskaya, 148 British Soya Products, 240 Bezostaya, 148-9 Brookfield, 9 BIAKS, 187, 477 Biihler Brothers, 216 Biotin, 245 Burkitt, D., 254 'Biplex' mixer, 262, 263, 264, 435-8 Bushuk, W., 66 BK oven, 158 Bushuk and Hulse, 461 Blanchard, G., 179, 182, 183, 224, 225 Bushuk et aI., 69 Blanchard process, 43, 179, 224-5 Butanol, 74 Bloksma, A. H., 66, 76, 328 BM-2, 158 BN 25 oven, 196,204 Calcium, 247, 248 BN 40 oven, 133, 134 Calcium bromate, 33, 35 BN 50 oven, 119, 120, 139, 204, 459, 627 Calcium iodate, 33, 34, 66 BN 72 oven, 204 Calcium peroxide, 33, 34 Bogdanov et aI., 73 Calcium stearoyl-2-lactylate, 39 B6hringer, 346 Canada Boku mixers, 260 baking tests, 332-3 Boku Spiral, 421 bread-making in, 294-8 Bolling and Zwingelberg, 96 Canadian Engineering Research Service, B6senberg and Eberhardt, 390 18 Brabender Amylograph, 82, 83, 315, 500-1 Canadian Grain Research Laboratory, Bradender-Do-corder, 10, 313 149 Bra bender Extensograph, 18, 36, 313 Canadian Hard Red Spring, 77, 296,461 Brabender Farinograph, 3, 148, 313, 501 Canadian Prairie spring wheat, 295 Brabender Glutentester, 307 Canadian Utility wheat, 295 Index 839

Canadian Western Red Spring, 51, 52, 229, Cysteine, 27-9, 36, 65, 76 266,294,462 L-Cysteine-HCl, 27, 28, 232, 235, 236,490 Canadian Western Red winter wheat, 295 Cystine, 36 Candida species, 353, 355, 478, 495 Czechoslovakia, 197-201 Carbohydrates, 3, 40 Carbon dioxide, 479, 480, 481, 486, 541, 599 Dal'nevostochnaya, 148 Carbon monoxide, 599 Daniels et al., 43, 74 Carboxyl methyl cellulose (CMC), 56, 57 Dark Northern Spring wheat, 266, 269 Carlson and Bohlin, 328 Dataa, 717 Carlson et al., 473, Deamination, 75 Carob bean flour, 55 Deck-ovens, 98 Cathcart and Luber, 709 Deep-freezing, 99 Cave!, R., 351 L-Dehydroascorbic acid, 32, 33 Cavenham Foods, 240 Dehydro-D-isoascorbic acid, 33 Cellophane, 681, 686 Dempster et aI., 18 Cellulose and derivatives, 55-8 Detmold baking test, 333 Central Soy, 44 Detmolder process, 346, 508 Ch-12 mixer, 175, 194 Detmold one-stage process, 106, 533 Charlock, 324-5 Detmold two-stage process, 106 Chefarox,216 Deuterium oxide, 76 Chernaya et al., 187 Dextrin, 31 Chlorine dioxide, 42, 43, 216 Diacetyl tartaric acid, 39, 40, 79, 235 Chopin Alveograph, 41, 90, 147-8 Diasoy,42 Chorleywood Bread Process (CBP), 25, Dierks, 260 182, 183,225,226,228,230,231, Dietary breads, 45, 522 267,317,491 Dietrich Reimelt, 207, 400, 401, 717 Chrenow, A. M., 194, 519 Diosna, 260, 261, 414, 419, 420 Chr. Hansen's Laboratorium, 352 Dirndorfer et al., 78 ChSM-300, 172, 176, 185, 194,519 Disinfectants, 380-1 ChTR, 170, 171, 176, 179,519 Disulphide bonding, 63-4 ChTU-D unit, 176, 177 Divider-moulders, 122 Citric acid, 59 Do-corder, 10 Claviceps purpurea, 323, 324 Do-maker, 28, 226, 280-1, 283, 443, 490 Clement wheat, 78 Donelson and Yamazaki, 316 Clostridium perfrigens, 382, 383, 385 Donezk Bread-factory No.2, 177 Cluskey and Wu, 76 Dontschenko, W. M., 171, 175, 176 Cluskey et aI., 672, 673 Do-Soy, 42 Coal, 598, 600 Dough Cohen et aI., 472 acidity, 484, 485 Cole, E. W., 81 additives, effects of, 27-59 Combination bakeries, 305 chemical changes in, 479-91 COMECON, collaboration in, 203-6 components, main, 22 Computers, 369,402,463,470,488,717 conditioners, 42 Continuous bread process, gluten addition, consistency, 27-29, 32-34, 82 49-53 deformation, 371-2 Convenience food, 255-6 elasticity, 67 Coppock, Dr, 183 fermentation, 479-91 Corn syrup, 338 freezing, 689-708, 715 Coventry et al., 36 gluten addition, 45-53 Crabtree effect, 470 measuring systems, 371-2 Cresta Doughmaster, 230 pH, 581-2 Crest Catering Equipment Limited, 252 proofer unit, 696-7 Cysteic acid, 36 proofing time, 39 840 Index

Dough-contd. Emmaflex C-700C, 632 relaxation time, 43 Emulsifiers, 40, 268 retardation, 98 Emulsions, 180, 181 retarders, 694, 695, 696 Emulthin, 45 rheological elements, 11-20, 539 Entain and Frohlich, 473 ripening, 18 Escherichia structure deformation, 11 coli, 326, 327, 385, 388 temperature and, 27, 28, 359-62 species, 388 testing apparatus, 313 Ethanol, 83, 481, 541 viscosity, 9, to, 11, 13, 17, 21, 29, 30 E.T. Oakes Limited, 226, 443, 444-5 water and, 24, 32, 35, 47 Ewart, J., 64, 76, 85 yield, 363-6 Extensigraph, 18, 19 Dough-making: chemical bonding, 60-85 consistency control unit, 25-6 Falling number, 31, 83, 84, 96, 315 model explaining, 3-8 Falunina, S. F., 540, 581, 583 stress relaxation, 28 FAO,149 temperature, 26 Farinogram, 67 water and, 16, 17,21-6 Farinograph, 16, 34, 76, 77, 148 Dough-mixing: Farrand, E. A, 54, 229, 317 control of, 366-71 Fatty acids, 180, 181,224 discontinuous, 10 Fermentation high-speed, 57 control of, 488 intensity, 9-10, 13,29 time for, 489, 490, 491 mixers, 11 Ferulic acid, 60, 80, 82 mixer types, 408-64 Fibre, 56, 254, 255, 256 mixer torque, 13-16 Flavobacterium, 326 parameters, 9-10, 11-20 Flavol, 278, 279 rpm, 10 Flour speed,29 acidity, 319-20, 350,484,485 time, 9, 10, 13,26 additive tests, 320-1 Doughnuts, 301-5 animal contaminants, 322-3 Dough-souring, 57, see also sour-doughs catalase, 322 DP 383P, 633 colour, 319 Drews, E., 81, 82, 97, 316 components, 21 DUO-NU oven, 610-17 evaluating, 327-33 Durum wheat, 269 gluten content, 306-9 improvers, 42 measurement and, 306-35 E221,29 mineral contaminants, detection of, 322 E223,29 particle size, 318-19 E300,42 pH,320 E466, 57 preparation, 362-3, 397 E471,38 protein-nitrogen measurement, 314 E472e,39 storage, 394, 395, 396, 402 E481, 39 strength, 485 E482, 39 structural elements, 60 E-924,229 thermal treatment, 327 Eberhardt, 260 vegetable contaminants, 323-5 EC vital wheat gluten and, 47, 52 additives and, 29, 34, 35, 38, 39, 42, 715 Flowers Bakery, 276, 277 tariffs, 49, 266 Folic acid, 245 Elion, E., 36 Food poisoning, 382-3, 387 Elsworth and Philipps, 66 Foramitti, A, 460 Index 841

Foremost Foods, 290, 706 Gerstenberg, H., 344 Foremost Whey Products, 279 Giacenelli, E., 34 France Gilbert mixers, 422 bread-making in, 86-90 Gill and Duffus, 244 dough mixing, 25 Ginsberg, A. S., 161 Frank, H. K., 390 Ginsburg, A. G., 183 Frank and Eyrich, 390 Girrek spirals, 261 Frazier et aI., 18 Gladkowa, E. A., 192 Freed, R. J., 282 Gliadin, 29, 39, 51,60, 61, 68~72, 74~76, Friabilin, 671~2 79,80 Fructose, 195, 337,473,480,481,482 Globulins, 3, 68, 73 FTK 1000, 126, 127, 204, 451~60 Glucanases, 335 FTK 1500, 127, 204 Glucose, 337, 473, 480, 481--483, 541 Fuchs, 133 Glutamic acid, 35, 75, 79 Fuchs, K., 499 Glutamine, 67 Fullington, J. G., 59 Glutaraldehyde, 85 Fumigants, 380 Glutathione, 33, 35~7, 76, 187,483 Fungicides, 391 Glutelins, 3, 61 Furfural, 655 Gluten analysis, 60 coagulation, 541 Galactolipids, 75 composition, 65 Galactose, 40, 55, 70, 83, 472 dough formation, 6, 19 Gatelin process, 168 drying, 45 Gatilin, N. P., 194 quality, 313 Gatilin, W. F., 167 solubility, 76 Gelinas et al., 470 stretching, 65 General Mills, 374 structure, 20 German Democratic Republic viscoelasticity, 39, 40 bread-making in, 108--43, 522, 526~8, water and, 23, 24~5 716~17 Glutenin, 20, 29, 39,40, 60, 61, 67, 69~73, dietetic breads, 115~ 16 76,78 Grain Processing Institute, 58, 135, 137 Glutomatic, 210, 307 national bread and rolls, 117~19 Glycerol, 481, 482 production lines in, 119--43 Glycine, 35, 77 quality control in, 108~ 10, 112~ 13 Glycolipids, 16,20, 71, 74, 75 rolls, 108, 117~19, 140 Glycoprotein, 20 special breads, 111 ~ 15, 136--43 Goldsmith, James, 253 Technical Control Organization, 109, Goodman Fielder, 244, 253 110 Gorky, Maxim, 144 TGL numbers, 108 Goroschenko, M. K., 167 TGL 27242/01, 110, 112~13 GOSTOL,422 TGL 2742/01, 110 Graham flour, 111 TGL-3067, 108, 522, 548, 578, 717 GRAS, 57 TGL 8029, 313 Graveland et al., 73 TGL 26972, 117 Great Britain. See United Kingdom wheat breads, 111 GRL-1000 mixer, 462, 463 wholewheat breads, 111 Grosskreutz, J. c., 50, 51, 65, 71 WTOZ, 142, 143 Grossman and Zimmermann, 472 Germany, Federal Republic of: Grunert et aI., 39 bread-making in, 96-108, 522, 523, 716 GSH, 36, 37 Grain Research Institute, 59 GSSG, 36, 37 rye-flours, 102~8 Guar gum, 705 wheat-flours, 97~ 102 Gupta, N. K., 161 842 Index

Haake, 9 IR spectroscopy, 70 Hagberg-Pertent, 315 Isernhager natural dough-souring, 460 Halton and Scott-Blair, 17 Isoascorbic acid, 33 Hansenula subpelliculosa, 91, 349, 353 Hard Red Spring, 37, 269 Jackson, G. M., 60 Hard Red Winters, 269 Jaroslawer bread-factory, 193 Harrel and Thorn, 602 Jazuba et aI., 21 Hawthorne and Todd, 222 Jegorowa et aI., 185 Hay, J. G., 42 Jelitzki and Semichatowa, 337 Hemicellulase, 335 Johnson, J. A., 278 Hemicellulose, 55, 56, 80, 81, 103,335 J0rgensen, H., 36 Henika and Rogers, 28 1. Rank Limited, 42 Hess, K., 50, 51, 65, 71 1. R. Short Milling Company, 42 Hexose, 337,480, 541 High-fibre breads, 524-5 High fructose corn syrup (HFCS), 41, 488, Karaya gum, 705 713 Karl-Marx-Stadt Bakery Cooperative, 136 High-protein breads, 525-8 Karpenko, F. P., 158 HLK 50 mixer, 140,414 Karpenko, V. I., 37, 187 Hoeppler Consistometer, 33 Kawamura et al., 20 Holas et aI., 80 Kawka and Gasiorowski, 41 Hookean element, 17 Kazanskaya, L., 194 Horizontal mixers, 262, 263, 428-38 Kelesov, I. M., 61 Hoseney et aI., 70, 74 Kemerovo Technical Institute, 53 Hovis, 242, 250 Kiev Bread-factory No.6, 177 Huber, H., 59 Kilborn and Tipples, 277, 296, 462 Humboldt-Universitat, 39 Kilborn et al., 463 Hungary, 196-7,522 Kim and D'Appolonia, 670, 671, 673 Hydrocolloids, 53--4, 78, 84, 705 Kjeldahl method, 314 Hydrogen bonding, 62, 63, 66, 67, 71, 75, Kline et al., 291 76,655 Kogan, M. A., 169 Hydrogen peroxide, 44 Kolesov, V. M., 80 Hygiene, 372-93 Koma CDS system, 698 Konova et al., 53 Kontinua mixer, 439, 441 lADY (instant active dry yeast), 476, 477 Kosmina, N. P., 80 ICC-Standard, 107, 108, 315, 316 Kosmina and Holas, 81 IDK-l,148 Kovbasa, V., 194 Ilyinych, K. E., 162 Krasnodar bread-making factory, 175, 178 IMK 150 mixer, 119, 120, 124,361,368, Kretowich and Vakar, 76 426-8 Krijaginicev, M. 1., 660-5, 667-669 Improver-wheat, 149, 150 Kuhn and Grosch, 83 India, 149 Kuninori and Matsumoto, 33 Instant active dry yeast, 468 Kusmenko, W. W., 176 In-store bakeries, 689 Kuzminskij et al., 328 GDR,140 KVT 1000, 127,205, 345,445-51, 509 UK, 241, 242, 244 K VT 1300, 202 USA, 287-91, 292, 305 KVT 1500, 127, 129, 130, 131-133, 135, Instron, 18, 19, 655, 678 136, 168, 198,205, 345,445, 509, International Society of Cereal Chemists, 510 206 KVT 1800, 127, 202, 205, 345, 445, 509 Ionic binding, 63 Kwafi, 190, 191,517,518 Ionowa, W. W., 178 Kyowa Hakko Isogyo Company Limited, Ireks-Arkady, 346 53 Index 843

Lactic acid, 44, 52, 55, 58, 59, 83, 103, 104, Lucny, M., 41 172, 313, 334, 340, 342-4, 350, Lutescens, 148 484-5, 505 Lutsishina, E. G., 20 Lactobacilli, 494, 495, 533 Lutsishina and Matyash, 67, 150 Lactobacillus acidophilus, 355, 356 L VF viscometer, 9 Lactobacillus alimentarius, 355 Lyons and Company, 217 Lactobacillus brevis, 91, 340, 341, 348, Lysine, 41, 45, 79, 85 349, 352, 353, 355, 356, 495, 496 Lactobacillus bulgaricus, 356 Lactobacillus casei, 355, 356, 495 McCarrison, Sir Robert, 256 Lactobacillus cellobiosus, 348 Ma Ching Yung et aI., 68, 75 Lactobacillus delbriickii, 104, 173, 186, MacDonalds, 267, 298 187, 350, 352, 485, 496 Machkamow, G. M., 162 Lactobacillus jarciminis, 355 MacRitchie, F., 72 Lactobacillus jermentum, 104,355, 356, Maillard reaction, 542, 587, 588, 589, 592, 495 594 Lactobacillus fructivorans, 355 Malfa-Kraftma-Brot, 529-30 Lactobacillus leichmanii, 496 Maltase, 336, 337, 478, 483 Lactobacillus plantarum, 92, 348, 349, Maltose, 54, 58, 84, 314-17, 337,472,480, 351, 352, 355, 356, 495, 496 583 Lactobacillus sanfrancisco, 291, 348, 493 Mamaril and Pomeranz, 77 Laignelet Dumas, 60 Mannose, 473 Lagansk bread-factory, 177, 178 Maple Leaf Mills, 297, 298 Langroller B 750, 90 Maris Huntsman, 78 Lecithin, 43-4 Marsakow, G. P., 167 Lee and Samuels, 66 Marssakov, G. P., 144 Lee et al., 391 Marston, P. E., 27-8 Lehmann and Dreese, 692 Martin process, 45 Lenard and Singer, 76 Maslow, I. N., 161 Leningrad bread-factories, 185 Maslow and Nikolajew, 163 Lerchental and M tiller, 17 Mass madre panaria, 91, 348,492 Leucine, 79 Maturox, 233 Leuconostoc mesenteroides, 348 Mauri Bros, 234 Leutenegger and Frei, 698 Maximat-Spiralknetautomat, 420 Lignin, 103 Maxwell's relaxation time, 17 Linoleic acid, 42 Mazur, P., 181 Lipids, 40, 43, 49, 59, 61, 70-6, 674-5 Mazur and Miller, 701-2 Lipoprotein, 16, 20 MB III mixer, 140 Lipoxygenase, 42, 60, 78,179,180,182, Mecham and Weinstein, 59 224 Mecham et al., 61 Liquefaction number, 83, 84 Mechanically developed doughs, 262 Liquid oxidation phase (LOP), 177, 179, Mecklenburger Landbrot, 138, 139, 528-9 180-1, 225 Medcalf et al., 81 Liquid pre-ferment, 181 Meissel, M. N., 183 Liquid-sour, 172, 185, 186-95 Meredith, P., 229 Liquid yeast, 172, 173, 175, 176, 185, Merritt, P. P., 695, 696 186-95 Metallic ions, 59 List, 443 Meuser et al., 83 Listeria, 707 Mayerhof coefficient, 473 Locust bean, 705 Mayer reaction, 549, 551 Longroller ELR 680, 98 Micheljew, A. A., 167, 169,571 Lorenz, K., 349 Microbiological examination, 325-7 Losa, A. I., 187 Miljukow, P. M., 174 Lucas Meyer, 45 Minel production lines, 189 844 Index

MOCKIP,313 Ovens-contd. Molasses, 187, 353, 470, 472 design, 602-17 Monhamer process 346, 508 dielectric, 597-8 Monod,353 electric, 596-7, 601 Monoglyceride, 40 energy recovery, 629-32 Mono mixers, 422, 423 energy sources, 596-602 Montgomery and Smith, 81 energy utilization, 558, 559 Moonen et al., 20 gas and, 559~60, 598-601, 619 Moore and Hoseney, 41 industrial, 607-19 Moscow bread factory No.2, 159 loading, 633-7 Moscow bread-factory No.3, 169 multi-deck, 545, 558-9, 603, 604, 606, 617 Moscow bread-factory No.4, 179, 184 rack,606-7 Moscow bread-factory No.5, 185, 186 reel,605-6 Moscow bread-factory No. 10, 169, 189 requirements, 556-8 Moscow bread-factory No. 12, 167, 169 ribbon burners, 620, 622 Moscow Technological Institute, 53 temperature, 98 MRS broth, 356, 357 thermometers, 601 Muffins, 298, 299 travelling-band tunnel, 211-13, 545, 546, Multi-grain breads, 523-4 550, 558, 577 Mycotoxins, 389, 390, 391 tray, 607-8, 618 types of, 602-19 unloading, 633-7 Nessler's reagent, 356 wire-band tunnel, 601, 609, 617, 625-6, Netherlands: Institute of Cereals, Flour 627 and Bread, 73 Oven spring, 28, 29, 541, 543 Neukom and Markwalder, 80, 82 OW-204,308 Newton, 8 Oxidants, 6, 19,34-5, 78, 268, see also Newton's law, 710 under names of Nguyen-Brem et al., 77 Oxygen transfer, 353 Nikolajew, B. A, 312 Nitrogen, 66, 353 NMR spectroscopy, 20, 37, 67, 70, 150 Pallagi-Bankfalvi, E., 73 Novadelox, 216 Pan-o-mat Roll Plant, 267 Novoukrainka, 149 Papain, 31 NU oven, 610 Paracolobacterium aerogencides, 326 Nutrex, 207 Paschchenko et al., 43, 181 Patt and Stscherbatenko, 163 PAU-1,308 Oase-Pumpen, 421 Pauling and Corey, 61 Odessa bakeries, 188, 189 Pawperow, A A, 167 Odesskaya, 149 Pawperow and Tschernjakow, 167 Ofelt and Smith, 41 Pediococcus cerevisiae, 348 Ofentriebgeriit,41 PEK-3A,308 Oils, 598, 599, 600, 601 Pekar test, 319, 320 Orla-Jensen, 356 Pelshenke and Schulz, 345 Clrsi and Pallagi-Bankfalvi, 20 Penetrometer, 308, 313, 338 Osborne et al., 68 Penicillium Osborne fractions, 67, 68-9 citrinum, 390 Ostrowski, A I., 172, 185,477 expansum, 390 Ovens Pentosanases, 55, 82, 83, 234, 484 batch, 603-7 Pentosans, 3, 19, 22-3, 25, 45, 79-83, 335, burner control, 620-4 484,541 control of, 620--9 Perkins ovens, 558 depanning, 635-7 Perlin, A, 81 Index 845

Pest control, 374-93 Protein-contd. Petroleum ether, 74 structure, 61, 65, 69 Pettri dish, 52 see also under names Pfeilsticker and Marx, 32 Protein Digestibility Index, 41 PFWS (pre-gelatenized flour/water Proteolipids, 51 suspension), 185-8 Pseudomonas, 387 Pharmacia AB, 316 PTC-24 oven, 196 Phenolic acid, 60 PTK 1000, 345 Phosphate, 353 PTK 1500,345 Phosphatic acid, 43 Pumpernickel, 115,500,530-2,684 Phosphatidyl choline, 43, 44 Puratos Corporation, 279 Phospholipids, 49, 59, 71, 72, 74, 75 Putschkowa, L. I., 309 Phytin,247 Pyrometers, 567 Pichia polymorpha, 91, 349 Pyruvic acid, 481-483 Pischia saitoi, 349, 353, 355, 495 Pitta bread, 251 Quasi-continuous process, 508-12 Pizzas, 251-4 Quellkurve, 82-84, 97 Plastometer, 309 Quellmehl, 344, 346 Plastometer AB-1, 151 Quellzahl, 313, 314 Plate-counts, 384, 385 Quellzahl-flasks, 52 Plotnikow, P. M., 193 Poland, 201-3 Polydextrose, 56 Rabe, E., 344 Polyethylene, 681-2 Rabinowitsch, I. L., 169, 170 Polypeptides, 61-5, 69, 73, 79, 80 Raffinose, 472 Polypropylene, 681 Rank Hay process, 42 Polythene, 214 Rank-Hovis, 217, 222 Pomeranz, Y., 72 Rank Hovis McDougall, 236, 237, 242, Ponte, J. G., 67, 279 243,248,253 Popaditsch and Falunina, 585, 586 Rank-Pullen meter, 367 Poponeau, Y., 67 Rebinger, P. A. 309, 312 Potassium bromate, 27, 28, 33-35,41,66, Reddi-Sponge, 279, 290, 706-7 77, 79, 85, 149, 232, 235 Redox potential, 67 Potassium carbonate, 136 Redox-systems, 321 Potassium chloride, 115 Redpoint THI-3oo thermometer, 632-3 Potassium iodate, 28, 33, 34, 35, 66, 177, Red Spring, 273 233 Red Winter, 273 Potato semolina, 139 Regotrans, 639 Potato starch, 31, 667 Rehrlich et al., 71 Potentiometer, 567, 592 Reimelt, 515 PPC ovens, 198 Resistance oven, 41 Pressed-yeast, 172,467, 476, 478 Retarder cabinet, 259 Pressure sheeting, 461-3 Retarder/proofers, 692, 693, 696, 697-9 Prihoda et al., 33 Reznichenko, M. S., 61 Procea, 207, 240 Rheo-Tech VER, 370 Prolamines, 3, 61 Rheotest 2, 9 Proline, 51, 67, 75, 79 Riplex mixer, 432 Proofer, automatic, 210-11 Rogers and Szostak, 475 Protein Rogers Fermitech Company, 275, 280 baking, changes in, 584-90 Rohrlich and Muller, 50 denaturation, 549, 585, 587, 669, 672 Roiter, I. M., 163,190, 191, 193 disaggregation, 29 Roiter et a/., 174 mixers and, 5 Rosedowns, 230 molecular surface, 17 Rothe et al., 590 846 Index

Rototherm 90, 629 Sievers, R. S., 565-6 Rotovisco RV-3, 9 Simmonds and Orth, 85 Rumsey-Ritter, 317 Simplex 2000, 616 Russel Finex Limited, 402 Sinapis arvensis, 324-5 Russia. See Union of Soviet Socialist Slimcea, 240 Republics Smith, D. P., 565 Rye proteins, 79 SM mixers, 425 Rye-bread Sodium bisulphate, 66 baking, 569 Sodium metabisulphite, 29-30 USSR, 190-5 Sodium stearoyl-2-lactylate, 39, 674 Rye-flour Sodium sulphite, 29-30 properties, 675-6 Soest, P. J. van, 56 wheat flour and, 86 Soft Red Winter, 269 Rye-sours, 492-7,500,501,502,512-13, Sorbic acid, 683-4 516, 519-21 Sotscha divider, 189 faults, 519-21 Sottoriva,419 Sour-dough, 340-58 acidity, 506, 511 S 70 divider moulder, 204, 459 bacteria, 104 S-125,414 baking-process, 513 S-250, 414, 423 consistency, 498 Saccharomyces drying, 347-8 cerevisiae 91, 193, 335, 340, 348, 349, flour quality, 500-1 351, 355, 467, 471, 472, 495 maturation, 504 exiguus, 291, 348,493 microflora, 355, 494, 495 fructuum, 91, 349 nutrients, 499 minor, 194,340,353 processing, 492-521 Saizew, N. W., 159, 169 processing stages, 501-21 Saizew et al., 185 process variables, 497-501 Salmonella, 382, 385, 392 standing time, 499-500 Salmonella enteritidis, 382 starter, 340 Salt, 28, 43, 58, 73 starter culture, 103, 104, 495 Salt-sour process, 508 temperature, 497-8 Sancassiano range, 420 USSR, 516-19 Sandstedt et al., 31 Sandstedt, R. M., 580 S. and W. Berisford, 244 Soy additives, 41-5, see also Soy flour Sanger and Edman, 61 Soya foods, 240 Saratovskaya, 148 Soy flour, 41-43, 75, 180,223-225,240 Sara tower system, 109 SP-80 systems, 400 Sarrubra, 148, 149 Spain, 90-2, 258, 348, 351 Schneeweiss, R., 206, 540, 581 SP-ALH 261,419 Schneeweiss and Klose, 639, 652 Specialty breads, techniques for, 522-35 Schneider, W., 81 Spicher, G., 355, 495 Schoch, T. 1., 580, 655, 659, 670 Spicher and Schollhammer, 349 Schulz, A., 59, 222, 340 Spillers, 183, 217, 236, 240, 244, 250, 253, Schulz and Stephan, 59 257 Scott, P. M., 391 Spindle-moulder, 209-10 SDS-electrophoresis, 20 Spiral mixers, 93, 259-62,417-23 Seibel et al., 532 SPP, 240,241, 250 Semolina, 110,269 -SS- bridges, 65, 233 Senti and Dimler, 660, 673 -SS- groups, 66, 77 Sephadex G-l00, 77 Staling, retarding, 40, 679-82 SH groupings, 32, 34, 36, 65, 66 Staphylococcus aureas, 326, 327, 383, -SH- groups, 77, 181,226,233 385-88 Index 847

Starch Trichosporon penicillatum, 349 baking, changes during, 580-4 Tscheuschner, H.-D., 161 damaged, 53-4, 316-17,484, 580 Tscheuschner and Auerman, 308 gelatinization, 40, 58, 540-1, 549, 578, Tschtscherbatenko, 174 665, 669 Tsen and Bushuk, 77 granules, changes, 23, 31 Turbo-radiant oven, 211, 212 particle size, 314-15 Tweedy mixers, 182,225,227,228,361, products added to dough, 54-5 368,402-3,407,422,423 retrogradation, 670, 671, 674 swelling, 3, 5 water and, 3, 23, 24, 25 UAD-15,184 Stepanova, O. N., 53 UAD-60,184 Stephan, H., 345 Uniflow oven, 211, 212, 215 Stoljarowa et al., 173, 490 Union of Soviet Socialist Republics Stoll and Bouteville, 324 Academy of Sciences, 76 Streptococci, 385, 386, 387, All-Union Institute for Grain and Subtilis mesentericus, 326 Grain-processing Research Suchumier bread factory No.2, 169 (WNIIS), 148 Sucrose, 195,337,338,472,480,482 All-Union Research Institute for the Sullivan, 8., 49, 60 Baking Industry (WNIIChP), 158, Sullivan et al., 77 160,170,173-5,179,188,193,477, Sulphuric acid, 31 478, 645, 647 Sulphydryl, 6, 34, 66 All-Union Scientific Research Institute Supertex, 208, 230 of Applied Molecular Biology and Surfactants, 37-41 Genetics, 73 SU-US 854349, 194 bakeries, number of, 145 Sverdlovsk bread factory, 167 baking tests in, 146-7 Switzerland, bread-making in, 92-4 bread, chemical composition, 165 bread, energy content, 166 bread-making in, 143-95 t940, 121, 198 bread varieties, 154-66, 195 t985, 121, 122, 124, 198 dough-processing in, 166-83 TCA, 474, 480, 482 flour, digestibility coefficients, 165 T. Collins Ltd, 218, 219 flour-milling, 151, 152 Technoplast,419-20 GOST, 146, 148, 151,328,490 Teltoma sour, 346 Moscow Technology Institute for the Tesco,242 Food Industry, 161 Thiol, 76, 77 State Standards, 150, 153 Thomas Collins, 416, 417, 419 Uniplex mixer 262,264,265,432-4 Thomson Pty Ltd, 234 United Kingdom Thorner, D., 460 Bakery and Allied Trades Association, TK-150,424 230 TLC,75 Bread and Flour (Amendment) TM-M,674 Regulations (1972),231,490 Toda and Yale, 474 Bread and Flour Regulations (1984), 52, Todd et al., 222 229, 235, 241 Tortosa et al., 75 bread-making in, 206-522 Torulopsis candida, 348 bread quality, 217, 222, 239 Torulopsis colluculosa, 348 bread varieties, 248 Torulopsis holm ii, 353, 355, 495 Food (Control of Irradiation) Transducers, 13, 16 Regulations Amendment (1972), 381 Traub et aI., 65 Food Labelling Regulations (1984), 52, Treloar's equation, 19, 20 229 Trichosporon margaritiferum, 91, 349 Horne-Grown Cereals Authority, 237-8 848 Index

United Kingdom-contd. Weigher-mixer functions, 394-9 milling, 216, 217, 236, 237, 244 Weighing methods, 399-408 National bread, 42, 208 Weisblatt, 327 National flour, 206, 207 Wendel-type mixer, 93 nutritional labelling, 254, 255 Werner and Pfeiderer, 90, 95, 98, 420, 439, United States of America 548,610 baking tests, 328-32, 335 Wheat-flour, rye-flour and, 86 bread-making in, 268-94, 534 Wheat-sours, 492-7,503 enrichment standards, 270 Whey, 28, 29 FDA, 31, 33-5, 39, 55, 525 Whey/cystein, 283, 285 milling, 272 Winkler, 300, 301 nutritional labelling, 270-2 Winkler GmbH, 718 pre-ferments, 274-7 Wohlgemuth procedure, 31 short-time dough processes, 277-94 Wolarowitsch, M. P., 309, 310, 312 sour-dough French bread, 291-2, 493, Woltman counter, 362 494 Wood-pulp, 56 sour rye bread, 272-3 Woychik et al., 76 sponge-dough in, 274, 277, 279 Wiinsche and Tscheuschner, 328 Urea, 76, 77, 353 URK-2,152 Xanthan,84 Xylose, 55, 81, 541 Van der Waals force, 64, 65, 67, 71, 666, 669, 674 Vangalev et al., 33 Yeast VATW-4 divider-moulder, 140 acidity, 342-3 VATW 515,124 cell structure, 183 VEB-Biickereimaschinenbau, 414, 423, 426 dead cells, 335 VEB Backwarenkombinat, 346 fermentation, 479-91 VEB Bakery Collective, 140 food,275 VEB Bakery Cooperative, 142 gassing power, 336, 337, 339, 467 VEB Metal-works, 142 glutathione, 37, 338-9, 478 VEB Priifgeriite, 9 measurements and, 335-40 Vercouteren and Lontie, 65 physiology, 471-4 Veron AV/AC, 84 post-fermentation technology, 476-8 Viscometer, 9, 10, 82, 83 pre-activation, 183-6 Vital wheat gluten, 45-53 propagation and production, 469-78 Vitbe, 250 shelf-life, 338 VNI, 460, 515 types of, 467-8 Vogl, A. E., 323 water content, 338, 339 Vones et al., 80 Yersinia enterocolitis, 382-3, 392 Voronezh Technological Institute, 181, 187

Zeleny, 313 Wall, 1. S., 69 ZGL proofer, 98 Walsh et al., 78 Zimmermann and Schmitt, 328 Wedge-protein, 51 ZNK proofer, 98 Wehrli and Pomeranz, 70 Zwingelberg et al., 532 Wehrli et al., 74 Zwitterions, 43