Joimsi LOWRY

THE CHEMIGAL GOIPOSITIOI, CERTAIN RHEOLOGICAL PROPERTIES, AHD THE SHORTMHO POTOR OP PAT by JOiMSi LOWRY A THESIS submitted to OREGOH STATE COLLEGE in partial fulfillment of the requirements for the degree of MASTER OP SCIENCE June 1960 APPROVED: Associate Professor of Poods and Nutrition In Charge of Major Head of Depsuptraent>i#t of Foods and nutrition Chairman of4, (-School Graduate Committee Dean of Graduate School Date thesis is presented ^f /&>/?&& Typed by Verna Anglemier ACKN0?JI*EDGEMENT The author wishes to express her deep gratitude to Miss Helen Charley for her careful direction of this research, her generous participation in it and her willing and able assistance in the preparation of this manuscript. My thanks are due her for her inspiration, guidance and invaluable advice in the progress of my academic and research work and in the preparation of the thesis. TABLE OF COKTHTS Page ISTTRODUGTIOK .....»......**..... 1 REVIEW OP LITERATURE .*............. S Hature of Fat ................... 3 Chemical Structure . * » 3 Theories of Patty Acid Distribution ..... 4 Even distribution ..... 4 Random distribution 5 Partial random distribution ...,.,* *j Restricted random distribution ..... 7 Melting Point ................ 8 Crystal Structure: Polymorphism 11 General 11 Fatty acids ............... 13 Triglycerldes . 13 Fats 17 Consistency 18 Content of solid material 19 Viscosity of the liquid phase SO Persistent supercooling ......... 20 Mechanical working ........... 21 Physical properties of the crystals ... 21 Chilling and tempering 23 Rheological Properties 24 TABLE OF COOTBHTS (continued) Page Methods of measuring * .'* . * « . * 25 Solids Content ............... 28 Dye»dilution method » * . * *'* * * * 28 Dllatometry «•.«•«•»»•*+•• 29 Pastry » .............. 34 Flour and Dough Ponaation ......... 34 Flour proteins ............ 34 Flour llpids ............. 35 Hydration of gluten .......... 36 Effect of fatty acids * . 37 Effect of monoglycerldes ....... 38 Shortening Power of Fat .......... 39 Effect of Manipulation , . 48 EXPERXMMTAL METHOD 51 Modification of the Lard .......... 52 Dilatometrlc Determination of Solids Content 54 Rheologlcal Tests ............. 56 Unworked penetration ......... 57 Apparent viscosity 58 Extrusion force ...... o .... 59 Pastry 62 Formula 62 Making the pastry • . 62 Measuring the breaking strength . 64 TABtE OF CCmHWTS (continued) Page RESULTS MD DISCUSSION .......**.,.. 66 Solid Pat Index ..... .... ..... 65 Rheological Tests ............. 67 iJnv/orked penetration ......... 67 Extrusion force . .......... 67 Apparent viscosity .......... 72 Breaking Strength of Pastry ........ 75 Breaking strength of pastry versus SFl 76 Breaking strength of pastry versus uOTorked penetration of fat ...... 78 Breaking strength of paltry versus extrusion force of fat ........ 78 Breaking strength of pastry versus apparent viscosity of fat 78 Breaking strength of pastry versus consistency of j&t ........... 81 Breaking Strength of Pastry (Series tl) ♦ . 87 Chemical Composition of the Lard and Breaking Strength of the Pastry ........... 88 Effect of glycerol . » 88 Effect of monoglycerides ....... 90 Short*chain saturated triglyceride versus long-chain unsaturated triglyceride ............. 90 Cis versus trans configuration . 91 Patty acid versus raonoglyoeride versus triglyceride « • • . 91 TABLE OF CaHTBMPS (continued) Pago STOMRY ■.'..•...•..>•.♦.*. ©5 BIBLIGGHAPHX: .*.♦»>.-. ♦ . , . • 98 APPENDIX .*,..*. * * .. i ..... 107 IiIST OF SABLES Table Page 1 Solid Fat Index of Modified Lards . 65 2 tJnworked Penetration of Modified Lards 68 3 Extrusion Force of Modified Lards • • 69 4 Apparent Viscosity of Modified Lards • 74 5 Breaking Strength of Pastry 76 6 Averages and Ranks for Solids Content and for Eheologlcal Tests of Modified Lards . 83 7 Breaking Strengths and Ranks of Pastry • . 88 8 Bffeets of Chemical Composition on the Breaking Strength of the Pastry and on the Consistency of the Lard . 89 (APPEHDIX) 9 Apparent Viscosity of Modified Lards • • 108 10 Breaking Strength of Pastry ...... 109 LIST (F FIGURES Figure Page 1 Arrangement of Fat lolecules Within t&e Crystals ................. 16 2 Extruder (assembled) . * ........ * 60 3 Relation between tferworked Penetration of Fat and Solid Fat Index . 70 4 Relation between Extrusion Force and Solid Fat Index ................. 71 5 Relation between Extrusion Force and Umrorked Fenatration ........... 7S 6 Relaticaa between Solid Fat Index and Breaking Strength of fastry #....♦.. 77 7 Relation between Unworked Penetration of Fat and Breaking Strength of Pastry .... 79 8 Relation between Extrusion Force of Fat and Breaking Strength of Pastry * * . * . » 80 9 Relation between Apparent Viscosity of Fat and Breaking Strength of Pastry ...... 82 10 Breaking Strength of Pastry and Consistency of Fat . 84 11 Relation between Consistency of Fat and Breaking Strength of Pastry in Ounces • . 86 THE CHEMICAL COIPOSITICM, CERTAIN KHEOLOGICAL PROPERTIES, MB TEE SHORTEHlia POWER OF PAT UTRGDTJCTIOI Pats are a necessary ingredient in cakes, breads and pastry because they coatribute tenderness. "The ability of a fat to lubricate and weaken the structure of a baked product is known as its shortening value" (2, p#279). Several investigators have attempted to relate the chemical composition or some other fundamental property of the fat to its shortening power bttt results have been variablB. Bailey has stated that "it would appear that the shortening value of fat is principally dependent upon its consistency, soft fats such as prime steam lard being superior in this respect to firmer fats, such as all- hydrogenated shortening1' (2, p,280). Harvey (26, p*1156} veported that increasing the plasticity of a fat increased its shortening value, but he did not measure the plasticity of the fat. Using a penetrometer to measure th© consistency of fats before and after working them. Hornstein et al. (31, p. 10-11) reported a "highly significant" correlation between the breaking strength of pastry and the consistency of the worked fat* They postulated that ®ie shortening power of a fat depends upon the ratio of liquid to solid glycerides. Scott Blair (69, p»401) stated that "surprisingly little quantitative information is yet available on rela- tionships between the rheologlcal properties and chemical constitution of fats, on the one hand, and the shortness or texture of baked products containing them, on the other." In the present study, the consistency of lard was deliberately varied by incorporating a fat or fatty derivative of known chemical composition. The effects of the addition of nine such substances on certain rheologlcal properties of the lard and on the shortening value of the lard were measured in an attempt to relate differences in rheologlcal behavior to differences in sha? tening power. Lard was chosen as the fat for this study because it was readily available without additives, because the fatty acid make-up and the glycerlde make-up is fairly well known and because lard is reputed to be an excellent shortening. ) mVIM OP LITEEATURE *-'*}■ Nature of Pat Chemical Structure Common food fats are esters of the trihydroxy alcohol, glycerol, and the higher fatty acids, chiefly palmitic, stearic, oleic and linoleic (15, p.3). Fatty acids may be attached at three positions on the glycerol molecule; these positions are designated simply as 1, 2, and 3 or as <* , P , and c* . If the three fatty acids are identical, the product is a simple triglyceride; if they are different, it is a mixed triglyceride (15, p. 166-167). Simple and mixed triglycerides are referred to as GSg, GUg, GUgS, and GSgtJ, wi th G representing glycerol, and S and^U representing saturated and unsaturated fatty acids, respectively. Carbons in the fatty acid chain are also designated". When numbered 1, 2, 3 and so forth, the carboxyl carbon is number 1. Hhen the Greek letters are used, the carboxyl carbon is not designated, the adjacent carbon being of • For unsaturated fatty acids, the symbol A with a numerical superscript is sometimes used to refer to the location of the double bond; thus. A® acids contain a double bond in the 9:10 position (24, p.1-2). "Because of the number of fatty acids and the fact that there are three positions oo each glycerol molecule to which the fatty acids may be attached, a large number of isomeric glycerides is possible in a single natural fat" (50, p.257). Theoretically, the number ©f possible combinations increases geometrically as the number of fatty acids increases; i« e., it equals nS where n repre- sents the number of different fatty acids. The number of chemically distinguishable glycerides is ^ (n3 plus n2) (39, p.211). The nature of a fat depends largely on the kind and proportion of fatty adds present in the triglycerld© (15, p.8). Theories of Patty Acid Distribution A number of theories have been advanced to account for the distribution of fatty acids among the molecules of natural fats and oils* These include the monoacld, the even distribution, the random distribution, the partial random distribution and the restricted random distribution theories* The monoaeid theory, based on the hypothesis that like acids form simple triglycerides, is n© longer accepted by most fat chemists (15, p.217). Even distribution. The even distribution theory, proposed by Hlldtich and co-workers, is as follows: When 5 any one fatty acid makes up approximately one-third of the total fatty acids in a fat, it will appear in nearly e^e^y trlglyeerid© molecule. If it makes up from

Load more