An Update on the Processing of High-Protein Rice Products

Review An update on the processing of high-protein rice products

Fred F. Shih

The component of protein in rice, at 7–9% by weight, is relatively protein, rice bran and, to a lesser extent, broken rice kernels, have been low, but the total amount of rice protein potentially available is signifi- under-used and under-priced. This report provides an update on the pro- cant because the production of rice worldwide, at 380 million tons cessing of these sources for rice proteins. Methods of protein processing annually, is huge. Rice proteins are recognized as nutritional, hypoaller- are highlighted including the traditional alkaline extraction, enzyme- genic, and healthy for human consumption, and rice protein products assisted extraction, and the novel uses of physical treatment prior to have been in demand in recent years. However, because of difficulties in water extraction. Also discussed are effects of processing on the func- the processing, rice protein products, particularly high-protein content tional and nutritional properties of rice protein. ones, have not been readily available. Two of the main sources of rice

Contents being low in content, proteins in rice are extremely insoluble in water, which makes them difficult to separate during 1 Introduction ...... 420 processing. As a result, the two main sources of rice protein, 2 Rice bran ...... 420 rice bran and broken rice kernels, have mostly been under- 2.1 Bran protein ...... 420 used and under-valued through the years. The industry used to 2.2 Alkaline extraction ...... 421 process broken rice kernels or rice flour for its starch and con- 2.3 Enzymatic methods ...... 421 sider the residual protein a co-product of little value and often 2.4 Physical methods ...... 422 a disposal concern [4, 5]. On the other hand, rice bran from the 3 Endosperm proteins ...... 422 milling of rice, in spite of being relatively rich in protein, has 3.1 Alkaline extraction ...... 422 mostly been ignored as a valuable resource because it contains 3.2 Enzymatic methods ...... 422 little of the desirable starch. Only in recent years when plant 3.3 Physical methods ...... 422 proteins in general and rice proteins in particular were recog- 4 Processing on functional properties ...... 422 nized to be exceptionally healthy and desirable for human con- 5 Processing on nutritional properties ...... 423 sumption, did the processing of rice proteins begin to get atten- 6 Concluding remarks ...... 423 tion from industry and rice research facilities. 7 References ...... 424 Rice proteins consist of four traditionally classified fractions based on solubility: albumin (water-soluble), globulin (salt- soluble), glutelin (alkaline-soluble), and prolamin (alcohol- soluble). Globulin (about 12%) and glutelin (about 80%) are 1 Introduction the major rice protein components. Water and alkaline solu- tions are, therefore, the solvents of choice for the processing of Rice is one of the leading food crops in the world, and in rice proteins. However, depending on the source of protein and recent years annual production of milled rice worldwide is the effect of solvent on the products, various processing about 380 million metric tons [1]. For about 50% of the world designs and methods have been developed through the years. population, mostly in Asian countries, rice is the staple diet and This review covers the development on the traditional alkaline provides 35–59% of energy consumed from foods [2]. The extraction, enzyme-assisted extraction and novel physical component of protein in rice, at 7–9% by weight, is relatively treatments prior to the extraction. The emphasis is on recent low, but it is a major source of protein for these rice-consuming processing trends, the production of high-protein rice products, people. Specifically, contribution of rice for protein in the diet and the processing effects on the functional and nutritional is 69.2% in South Asia and 51.4% in Southeast Asia [2]. Plant properties of the products. proteins have been recognized to be nutritionally equal, if not superior, to animal proteins, and rice proteins have the added advantages of being hypoallergenic and healthy for human consumption [3]. Indeed, rice proteins have been in great demand 2 Rice bran for health-conscious consumers, and efforts are being made to 2.1 Bran protein develop new rice protein products to meet these needs. High-protein rice products have become commercially avail- Rice bran is a particularly attractive source of protein able only recently, especially in traditionally low rice-consum- because it is protein-rich, plentiful, and low-cost. Rice bran ing countries such as the United States. The reason for the lack comprises about 10% by weight of rough rice (Fig. 1), with an of interest in these products in the past is that, in addition to annual yield of about 50 million metric tons worldwide as a co-product from the milling of rice. It contains about 12% pro- Correspondence: Fred F. Shih, USDA-ARS-SRRC, 1100 Robert E. tein (Table 1) but is used primarily as animal feed. Efforts to Lee Blvd, New Orleans, LA, USA, 70124 add value to this co-product have not been totally successful E-mail: [email protected] Fax: +504-286-4419 because of difficulties in the processing of the protein component. Rice proteins are believed to be bonded strongly by di- Keywords: Review / Rice bran / Rice protein / sulfide linkages forming high-molecular-weight complexes,

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and electrophoretic profile for the extracted protein products [14, 15]. Generally, alkaline conditions are effective in solubilizing and extracting protein from rice bran, but alkaline extraction has its shortcomings. High pH alkaline conditions could lead to undesirable protein modifications including molecular cross-linking and rearrangements resulting in the formation of toxic compounds such as lysinoalanine [16, 17]. Molecular denaturation and degradation often occur, which reduce the food-use functional property and nutritional quality of the protein [14, 18, 19].

2.3 Enzymatic methods For food-use purposes, high-protein products from rice bran are often and preferably produced by enzymatic methods. Enzyme-assisted water-extraction of protein from rice bran has been studied using various food grade enzymes [20]. In general, proteases were reported to be more effective than carbohydrases in enhancing the protein extractability, but the pro- Figure 1. Yields of co-products from the milling of rice. From the teins recovered by proteolysis were protein hydrolysates that USA Rice Council. might not maintain their original structural and functional properties. In a similar study, Hamada [21] reported a proce- Table 1. Proximate protein content of rough rice and its milling frac- dure for the preparation of rice protein isolate using alkaline tions protease. However, at low degrees of hydrolysis (a2%) when Rice fraction Crude protein (g N65.95) protein degradation was insignificant, the improvement in protein extractability remained low. On the other hand, at high Rough rice 5.6–7.7 degrees of hydrolysis when A90% protein was extractable, the Brown rice 7.1–8.3 functional and nutritional properties of the extracted protein Milled rice 6.3–7.1 may be adversely affected. More general processes involve the Rice bran 11.3–14.9 use of carbohydrate-hydrolyzing enzymes such as cellulase, Rice hull 2.0–2.8 pectinase, hemicellulase, and xylanase to remove the cell wall tissues and thus enhance the extractability of the entrapped From [27] protein components [22–24]. Pretreatment of rice bran with commercially available carbohydrases was shown to enhance which are extremely insoluble in water [6–9]. Furthermore, the nitrogen extractability up to 57% [22]. In a particularly because of the presence of lipid, which is easily hydrolyzed by successful extraction, as shown in Fig. 2, rice bran protein iso- lipase or oxidized causing rancidity in rice, rice bran needs to late containing about 92% protein was prepared from unstabi- be stabilized such as by heat or acid treatment to deactivate the lipase or by defatting to remove the lipid [10–12]. These treatments could cause protein denaturation or aggregation which reduces protein solubility and makes the processing of rice bran proteins even harder to achieve.

2.2 Alkaline extraction High-protein rice products can most conveniently be obtained from rice bran by alkaline extraction followed by pre- cipitation at the isoelectric pH of the protein. Typically, Connor et al. [13] extracted full-fat rice bran with dilute sodium hydroxide at 248C, followed by separation of the fibrous residue with acid and heat, and produced protein concentrates containing 33–38% protein by weight. Prakash and Ramanatham [14] reported that, under optimum conditions of extraction at pH 11 and the follow-up acid separation at pH 4, contents of protein concentrations obtained from untreated rice bran and acid stabilized rice bran were in the range of 71–73% whereas protein concentrates from heat stabilized rice bran and parboiled rice bran had lower protein contents of 39.5% and 54.5%, respectively. Similarly, commercially available unstabi- lized and heat-stabilized rice bran were extracted in a slurry at pH 9.5 for 30 min resulting in protein concentrates with protein content of 71.5% and 50.9%, respectively [15]. Invariably, heat stabilization not only impaired the extractability of the Figure 2. Procedure for the preparation of protein isolate from protein in bran but also changed the amino acid composition defatted rice bran. From [23]. i 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Nahrung/Food 47 (2003) No. 6, pp. 420 – 424 421 Shih lized and defatted rice bran using phytase and xylanase [23]. possible, but not practical, to produce rice isolate with A90% However, prior to the recovery of the protein, the enzymes protein from milled rice or regular rice flour. An alternative is were deactivated by adjusting the reaction mixture to pH 10. to use as starting material protein-rich co-products from the Therefore, in addition to the enzyme function, the treatment processing of rice ingredients, such as in syrup manufacturing. under alkaline conditions may also contribute to the enhance- After removing the hydrolyzed starch as syrup, the insoluble ment of the protein extractability. residue contains up to 50% protein and is a low-cost industrial co-product [30, 33]. Shih and Daigle [34] reported that treat- 2.4 Physical methods ment of this co-product with a-amylase and glucoamylase resulted in a product containing 85% protein. Follow-up treat- Physical methods are often more desirable than chemical or ment with a mixture of cellulase and xylanase raised the pro- enzymatic methods in the processing of food, because they tein content to 92%. Inorganic impurities, particularly the normally induce less unnatural alterations in food and cause metal manganese that was present at an undesirably high level less health concerns. Anderson and Guraya [25] used high- of 47 mg/kg in the starting rice flour, were also removed from speed high-shear milling prior to water extraction in the pro- the protein product. cessing of rice bran and reported moderate successes in the separation of rice proteins. For full fat rice bran, the protein 3.3 Physical methods content of the supernatant increased from 21.8 to 33.0% after the high-speed high-shear colloid milling, and to 38.2% with a Physical methods have been reported for the endosperm pro- further homogenization treatment. For defatted rice bran, the tein separation. When slurry of rice flour was emulsified in the numbers were much lower after similar treatments, increasing presence of sodium stearoyl lactylate, the emulsion that was from 13.9 to 14.7% and to18.7%, respectively. formed separated into two layer fractions on centrifugation [35]. The upper fraction contained 48.5% protein on dry basis, and the lower fraction contained only 1.6% protein. Air classification and electrostatic separation have been investigated for 3 Endosperm proteins rice protein preparation [36]. Rice flour containing up to 17.5% protein was obtained by recovering protein-rich parti- 3.1 Alkaline extraction cles with size around 40 lm during the air classification of Rice flour from milled rice or broken kernels contains endo- regular rice flour. Electrostatic separation was effective in pro- sperm storage proteins, about 7% by weight, and these proteins cessing coarse rice flour (over 100 lm), in which the nega- appear to be more readily available for extraction than the pro- tively charged protein-rich coarse flour was attracted to the teins in rice bran. As expected, alkaline solvent is effective in positive electrode under the potential around 2.5 kV. facilitating the extraction of the endosperm proteins. Up to 97% of the protein, mostly in the form of glutelin, can be extracted by using 0.1 N sodium hydroxide or potassium 4 Processing on functional properties hydroxide [6, 8]. However, in practice, the alkaline treatment of rice flour is seldom used for protein processing, but serves Compared with other plant proteins, rice protein has rela- instead to remove the endosperm proteins for starch produc- tively poor food-use functional properties [37]. Rice proteins tion. Similarly, alkaline protease digestion of endosperm pro- are extremely insoluble because of intermolecular disulfide tein has also been used for the recovery of the starch [26]. Pro- linkages and high molecular weights of the major protein glu- tein in the effluent is normally discarded or recovered for use telin [6–9]. The solubility and other food-use functional prop- in feeds [27]. erties are further reduced during processing, particularly by modifications such as heat treatment for bran stabilization [18, 3.2 Enzymatic methods 38–40]. Functional properties can also be influenced by the Because the major component in rice flour is starch, starch- hydrolyzing enzymes such as a-amylase, glucoamylase, and Table 2. Bulk density, water absorption capacity and fat absorption pullulanase are often used to separate the protein in rice flour capacity of rice bran protein concentrates by solubilizing and removing the starch. Depending on the processing conditions in the production of the rice flour and the Rice bran protein Bulk density Water absorp- Fat absorption enzymic treatment, protein content of the resulting products concentration tion capacity capacity (gNmL) (mLNkg–1) (mLNkg–1) ranges from slightly enriched (25% protein) to highly enriched (A90% protein). They are commonly referred to as rice protein Freezed-dried: concentrates, except when the protein content is higher than Untreated 0.35 l 0.01 2400 l 10.4 2600 l 2.3 90%, and then they are called rice protein isolates. High pro- Acid-stabilized 0.33 l 0.02 2380 l 8.8 2700 l 11.0 tein rice flours with protein contents in the range of protein Heat-stabilized 0.30 l 0.02 2000 l 11.7 3200 l 12.3 concentrate have been produced for early childhood feeding by Parboiled 0.57 l 0.03 2000 l 12.8 3200 l 12.3 destarching treatments of rice flour or broken rice with a-amy- Cabinet-dried: lase, glucoamylase or glucose isomerase [28–31]. Morita and Untreated 0.66 l 0.03 1600 l 12.1 1500 l 3.5 l l l Kiryama [32] achieved the processing of protein isolate by Acid-stabilized 0.63 0.02 1700 21.3 1200 5.7 Heat-stabilized 0.70 l 0.04 1500 l 15.6 1400 l 9.6 treating rice flour with heat-stable a-amylase at 978C for 2 h. Parboiled 0.88 l 0.04 1800 l 9.8 1400 l 10.5 As starting material, the flour was obtained at 70% milling. Roller-dried: The product, after washing off the solubles with boiling water, Untreated 0.60 l 0.05 2400 l 7.6 1600 l 8.6 was recovered with a protein content A90%. Acid-stabilized 0.66 l 0.05 2400 l 12.9 1600 l 1.1 Because milled rice and rice flour are sold at premium prices and they contain only a small amount of protein, it is From [18]

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Table 3. Mean nutritional properties of various raw and processed rices

Balance data in five growing rats

Rice type Crude protein Lysine True Biological Net protein Lysine Cysteine digestibility value (% utilization digestibility digestibility (% N66.25) (g/16 gN) (% of N intake) of digested N) (% of intake) (% of intake) (% of intake)

Rawb) 8.9 3.6 99.7 67.7 96.8 99.9 99.5 Processedb) 9.0 3.5 88.6 78.2 95.4 99.4 82.0 Rawc) 11.8 3.5 99.1 68.8 97.0 – – Processedc) 12.7 3.5 85.8 73.7 92.5 – – a) Cooked and freeze-dried after being milled b) Low-protein rices (IR29, IR32, IR450-5-9) c) High-protein rices (IR58) From [27] drying technique employed [18, 41]. Freeze-dried protein con- ing protein digestibility. It also cross-links the protein mole- centrates from both heat-stabilized and parboiled rice bran had cules, inhibiting digestive enzyme reactions, thus lessening the low water absorption capacity and high fat absorption capacity digestibility of the protein. Based on in vitro enzymatic essay, (Table 2). Cabinet-dried samples did not exhibit any foaming thermal processing of foods, such as boiling, parboiling, and or emulsification capacity, indicating significant molecular extrusion, increases the digestibility of rice proteins [53]. In in denaturation [18]. vivo essay for protein digestibility, food is fed to rats under Rice albumin, globulin, prolamin, and glutelin have been various conditions, and the digestibility is measured by formu- extracted and the processing effects characterized using gel las in terms of nitrogen intake and out put. True digestibility electrophoresis, differential scanning calorimetry, and surface (TD) is calculated, taking into consideration of the nitrogen hydrophobicity [42–44]. Ju et al. [44] reported denaturation output due to non-protein components such as fibers that are temperatures of 73.3, 78.9, and 82.28C and enthalphy values involved in the diet [54]. Also calculated is the net protein uti- of 2.88, 3.14, and 3.79 J/g for albumin, globulin, and glutelin, lization (NPU), a combined measure of digestibility and the respectively. Prolamin did not show any thermographic dena- efficiency of the utilization of the absorbed amino acids. Heat turation peak. Also, heat-denaturation of globulin and glutelin treatment has been reported to reduce the true digestibility of resulted in progressive increases in their hydrophobicities. rice protein in rats by 10–15% (Table 3) [55]. However, the Cooked rice stickiness was reported to increase by the dis- treatment improves the biological value of the protein such ruption of the disulfide linkages in the protein component that NPU in rats is not reduced. Parboiling also reduces TD but [45–47]. Proteins from the outer layers of rice kernel, tightly increases biological value correspondingly without any adverse bound to the starch, were found to be responsible for reducing effect on NPU. The poorly digested protein, which passes out the pasting and crystallizing capacities of the starch [48]. Pro- of the alimentary system as fecal protein particles, represents tein content has also been reported to correlate negatively with the lipid-rich core proteins that are poor in lysine but rich in the expansion ratio for gun-puffed milled rice or oil-puffed cysteine [56, 57]. parboiled rice [49]. It is negatively correlated with peak visc- In addition to amino acids, processing could also alter or osity and positively correlated with pasting temperature of the remove other protein subunits and polypeptides, resulting in isolated rice starch [50]. changes in nutritional properties. As discussed earlier, high-pH treatment in alkaline extraction of protein could alter and con- vert protein ingredients into toxic compounds such as lysino- 5 Processing on nutritional properties alanine [16, 17]. On the other hand, processing may enhance or improve rice protein to eliminate anti-nutritional factors. Wata- Processing of rice proteins involves various physical and nabe et al. [58] treated milled rice with a surfactant and chemical treatments, which could affect, often adversely, the enzyme mixture to prepare a hypoallergenic milled rice grain. nutritional value of the protein. Most thermal processes cause In clinical tests, this hypoallergenic rice can dramatically decomposition of lysine and/or cysteine to various extents [51, improve rice-associated atopic dermatitis [59]. However, the 52]. In general, rice protein, like most cereal proteins, is defi- enzyme treatment is expensive and not suitable for mass pro- cient in the essential amino acid lysine, but has excess of the duction. Alternative approaches have been reported including essential sulfur-containing amino acids, cystine and methio- simple alkaline extraction to remove the antigens [60] and nine. The lysine contents of home-prepared baby foods were genetic modification to achieve the hypoallergenization [61]. damaged to a greater extent at 150–1608C compared with 100–1108C [52]. On the other hand, all the breakfast cereals processed commercially had levels of lysine reduced by 35– 6 Concluding remarks 76% and arginine by 10–41%. Extrusion cooking of milled rice batter at 15% moisture and 120–1508C reduced total In spite of their limited food-use functional properties, rice lysine content 11–13% and cysteine 14–29% but had no effect proteins have been successfully utilized in foods. For years, on tryptophan or cystine. with rice proteins as a key ingredient, rice flour or rice bran Heat processing of food affects the digestibility of the pro- has been incorporated in foodstuffs such as bread, beverages, tein component in different ways. It modifies the tertiary and pasta, and confections [12, 62, 63]. As high-protein rice prod- secondary protein structure causing denaturation, thus increas- ucts become more available, the use of rice protein in foods i 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Nahrung/Food 47 (2003) No. 6, pp. 420 – 424 423 Shih surges. It has been used in infant foods [29], breakfast cereal [30] Chen, W. P., Chang, Y. C., J. Sci. Food Agric. 1984, 35, 1128– [64], snack foods [65], hypoallergenic protein products [58], 1135. and edible films [66]. However, as shown in the above review, [31] Griffin, V.K., Brooks, J. R., J. Food Sci. 1989, 54, 190–193. even though much has been achieved in processing rice pro- [32] Morita, T., Kiriyama, S., J. Food Sci. 1993, 58, 1393–1396, teins, fully effective processing methods, particularly on the 1406. [33] Shaw, J. F., Sheu, J. R., Biosci. Biotechnol. Biochem. 1992, 56, extraction of rice bran proteins remain to be developed. More 1071–1073. work needs to be done to improve on what has been accom- [34] Shih, F. F., Daigle, K. W., J. Am. Oil Chem. Soc. 2000, 77, 885– plished, better understand the chemistry of rice protein, and 889. meet the challenge of fully utilizing the unique product of rice [35] Kung, L., Chen, H., Sung, H., J. Chin. Agric. Chem. Soc. 1987, proteins. 25, 299–307. [36] Noguch, A., Sato, O., Haque, Z., Saio, K. J. Jap. Soc. Food Sci. Technol. 1981, 28, 405–411. [37] Barber, S., Barber, C. B., in: Barber, S., Tortosa, E. (Eds.), Proc. 7 References Rice By-Products Utilization, Instituto de Agroquimica Y. Techo- logia de Alimentos, Valencia 1974, pp. 1–94. [1] United States Department of Agriculture, Economic Research [38] Knorr, D., J. Food Process. Eng. 1982, 5, 215–230. Service, Rice Outlook, March 12, 2003. [39] Knorr, D., Betschat, A. A., Starch/Strke 1983, 35, 23–28. [2] Juliano, B. O., Rice in Human Nutrition, FAO and IRRI, Rome [40] Devi, K., Geervani, P., Sumathi, S., J. Food Sci. Technol. 1997, 1993. 34, 345–347. [3] Helm, R. M., Burks, A. W., Cereal Foods World 1996, 41, 839– [41] Tang, S., Hettiarachchy, N. S., Horax, R., Eswaranandam, S., J. 843. Food Sci. 2003, 68, 152–157. [4] Juliano, B. O., in: Whistler, R. L., BeMiller, J. N., Paschall, E. F. [42] Chrastil, J., J. Agric. Food Chem. 1992, 40, 683–686. (Eds.), Starch: Chemistry and Technology, Academic Press, [43] Tang, S., Hettiarachchy, N. S., Horax, R., Eswaranandam, S., J. Orlando, FL 1984, pp. 507–528. Food Sci. 2003, 68, 152–157. [5] Kempf, W., Starch 1984, 36, 333–341. [44] Ju, Z.Y., Hettiarachchy, N. S., Rath, N., J. Food Sci. 2001, 66, [6] Cagampang, G. B., Cruz, L. J., Espiritu, S. G., Santiago, R. G., 229–232. Juliano, B. O., Cereal Chem. 1966, 43, 145–155. [45] Hamaker, B. R., Griffin, V.K., Cereal Chem. 1990, 67, 261–264. [7] Sawai, H., Morita, Y., Agric. Biol. Chem. 1968, 32, 496–500. [46] Hamaker, B. R., Griffin, V. K., Moldenhauer, K. A. K., J. Food [8] Tecson, E. M. S., Esmama, B. V., Lontok, L. P., Juliano, B. O., Sci. 1991, 56, 1327–1329, 1346. Cereal Chem. 1971, 168–181. [47] Hamaker, B. R., Griffin, V. K., Cereal Chem. 1993, 70, 377– [9] Sugimoto, T., Tanaka, K., Kasai, Z., Agric. Biol. Chem. 1986, 50, 380. 3031–3035. [48] Yang, C.-H., Chang, W.-H., Food Sci. Agric. Chem. 1999, 1, [10] Sayre, R. N., Saunders, R. M., Enochian, R. V., Schultz, W. G. 277–285. Beagle, E. C., Cereal Foods World 1982, 27, 317–322. [49] Villareal, C. P., Juliano, B. O., Cereal Chem. 1987, 64, 337–342. [11] Prabhakar, J. V., in: Sheth, B. M., Mehta, B. V. (Eds.), Handbook [50] Lim, S. T., Lee, J. H., Shin, D. H., Lim, H. S., Starch/Strke on Rice Bran, Solvent Extractors Association of India, Bombay 1999, 51, 120–125. 1987, p. 330. [51] Juliano, B.O., Trans. Nat. Acad. Sci. Technol. (philipp.) 1985, 7, [12] Saunders, R. M., Cereal Chem. 1990, 35, 634–636. 205. [13] Connor, M. A., Saunders, R. M., Kohler, G. O., Cereal Chem. [52] Eggum, B. O., Juliano, B. O., Ibabao, M. B., Perez, C. M., Food 1976, 53, 488–496. Chem. 1986, 19, 235–240. [14] Prakash, J., Ramanatham, G., Nahrung 1994, 38, 87–95. [53] Sagum, R., Arcot, J., Food Chem. 2000, 70, 107–111. [15] Gnanasambandam, R., Hettiarachchy, N. S., J. Food Sci. 1995, [54] FAO/WHO/UNU, WHO Tech. Report Series 724, World Health 60, 1066–1069, 1074. Organization, Geneva 1985, p. 118. [16] Cheftel, J. C., Cuq, J. L., Lorient, D., in: Fennema, O. R. (Ed.), [55] Eggum, BO., Resurreccion, A. P., Juliano, B. O., Nutr. Rep. Int. Food Chemistry, Marcel Dekker, New York 1985, p. 245. 1977, 16, 649–655. [17] Otterburn, M. S., in: Phillips, R. D., Finley, J. W. (Eds.), Protein [56] Tanaka, Y., Resurreccion, A. P., Juliano, B. O., Bechtel, D. B., Quality and the Effects of Processing, Marcel Dekker, New York Agric. Biol. Chem. 1978, 42, 2015–2023. 1989, p. 247. [57] Resurreccion, A. P., Li, X., Okita, T. W., Juliano, B. O., Cereal [18] Prakash, J., Ramanatham, G., J. Sci. Food Agric. 1995, 67, 181– Chem. 1993, 70, 101–104. 187. [58] Watanabe, M., Miyakawa, J., Ikezawa, Z., Suzuki, Y., Hirao, T., [19] Prakash, J., Ramanatham, G., Int. J. Food Sci. Nutr. 1995, 46, Yoshizawa, T., Arai, S., J. Food Sci. 1990, 55, 781–783. 177–184. [59] Watanabe, M., Trends Food Sci. Technol. 1993, 3, 125–128. [20] Hanmoungjai, P., Dyle, D. L., Niranjan, K., J. Chem. Technol. [60] Ikezawa, Z., Tsubaki, K., Okuna, H., Shimada, T., Moteki, K., Biotechnol. 2002, 77, 771–776. Sugiyama, H., Katsunuma, K., Anzai, H., Amano, S., Areugi [21] Hamada, J. S., J. Food Biochem. 1999, 23, 307–321. 1999, 48, 40–49. [22] Ansharullah, J., Hourigan, J. A., Chesterman, C. F., J. Sci. Food [61] Nakamura, R., Matsuda, T., Biosci. Biotechnol. Biochem. 1996, Agric. 1997, 74, 141–146. 60, 1215–1221. [23] Wang, M., Hettiarachchy, N. S., Qi, M., Burks, W., Seibenmor- [62] Lynn, L., in: Milner, M. (Ed.), Protein Enriched Cereal Foods gen, T., J. Agric. Food Chem. 1999, 47, 411–416. for World Needs. American Association of Cereal Chemists, St. [24] Shih, F. F., Champagne, E. T., Daigle, K., Zarins, Z., Nahrung Paul, MN 1969, p. 62. 1999, 43, 14–18. [63] Carroll, L. E., Food Technol. 1990, 44, 74–76. [25] Anderson, A. K., Guraya, H. S., J. Am. Oil Chem. Soc. 2001, 78, [64] Bakar, J., Hin, Y. S., J. Food Process. Preserv. 1985, 8, 163– 969–972. 174. [26] Lumdubwong, N., Seib, P. A., J. Cereal Sci. 2000, 31, 63–74. [65] Capansana, M. V., Cilindro, A. G., Martin, A. M. J., Garcia, E. I., [27] Juliano, B. O., Hicks, P. A., Int. Rice Commun. Newsl. 1993, 39, Guerrero, A. C., NSTA Technol. J. Natl. Sci. Dev. Board 1984, 163–179. 9, 58–72. [28] Resurreccion, A. P., Juliano, B. O., Eggum, B. O., Nutr. Rep. Int. [66] Shih, F. F., Cereal Chem. 1996, 73, 406–509. 1978, 18, 17–25. [29] Hansen, L. P., Hosek, R., Callan, M., Jones, F. T., Food Technol. Received May 7, 2003 1981, 35, 38–42. Accepted July 14, 2003

424 Nahrung/Food 47 (2003) No. 6, pp. 420– 424 i 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim