30C-3 |
Enzyme catalyzed peptides from heat-stabilized and defatted rice bran (HDRB) |
R. Cai, N. S. HETTIARACHCHY, R. Horax, and A. Davis. Department of Food Science, University of Arkansas, Fayetteville, AR 72704 Proteins in heat-stabilized and defatted rice bran (HDRB) are difficult to be extracted since heating decreases the solubility of proteins through denaturation and complexing with other components. New efficient methods for protein extraction could add value to rice bran. Enzyme-aided approaches are methods that could preserve the functionality of proteins while improving extraction efficiency since they require gentle conditions and extract proteins that are otherwise insoluble. Our objective was to evaluate the role of selected enzymes in hydrolyzing proteins and to characterize peptides from rice bran matrix. Five enzymes were studied, including a xylanase, a fungal protease, proteinase A, Econase CEP and umamizyme protease. Rice bran proteins were extracted using aqueous solutions with these enzymes at their optimum conditions. The protein contents of the extracts were determined using a 2300 Kjeltec Analyzer Unit. Extracted proteins were characterized using gel electrophoresis. Results indicated that there was a 128% increase in the amount of protein extracted with proteinase A (10,000 U/100 g rice bran) treatment compared to control. There were 15%, 5%, 39% and 62 % increases in the amount of protein extracted using xylanase (3,000,000 U), fungal protease (500,000 U), Econase CEP (100,000 U) and Umamizyme (70 U), respectively, in 100g rice bran. Gel electrophoresis indicated that proteinase A treated protein showed major bands at 55, 46, 27 and 20 kDa. Umamizyme protease treated protein showed major bands at around 35 and 12 kDa. Fungal protease extracted proteins showed major bands at 38 and 28 kDa, whereas Econase CEP and xylanase treated proteins showed bands below 15 kDa. Our results suggest that enzyme-aided procedures extract more proteins than controls, with proteinase A being most effective. Enzymes produced different polypeptide segments not observed with the controls, suggesting the release of these peptides from the rice bran matrix through enzymatic hydrolysis.
Session 30C, Food Chemistry: Proteins
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