30C-7 |
Protein extraction from heat-stabilized defatted rice bran: II. The roles of amylase, celluclast, and viscozyme in protein extraction |
S. Tang and N. S. HETTIARACHCHY. Department of Food Science, University of Arkansas, Fayetteville, AR 72704 Rice bran contains various amounts of starch (10-55%) and protein (6.7-22%). Rice bran goes through a heating process to preserve its oil quality, and heat treatment leads to protein denaturation and protein-starch interaction. We hypothesized that amylase can hydrolyze starch in heat-stabilized defatted rice bran (HDRB), and release the bound protein. The objectives of this research were to evaluate the effectiveness of a-amylase celluclast and viscozyme, and optimize conditions for extracting protein from HDRB. Rice bran was suspended in deionized water in varying ratios and different levels of amylase/celluclast/viscozyme were added to extract protein from HDRB. Box-Draper saturated design was used to optimize conditions, including amylase concentration, water to bran ratio, temperature, and time. The extracted protein was determined by Kjeldahl method. Amylase treatment extracted approximately 40% of protein from HDRB, when water to bran ratio of 10:1 was used, while celluclast and viscozyme extracted about 11-12% and 13-25% of protein, respectively. Response surface analysis showed that protein extractability increased from 9.5-58.4% with a-amylase concentration (0 to 110000 units/10g rice bran), time (1 to 8 h), ratio (5:1 to 20:1) and temperature (35 to 55 oC). The highest extractability accomplished was 58.4% under the conditions of 87637 units/10g rice bran, 4.5 h incubation, 17:1 ratio and 50.9 oC. A quadratic mathematical model was also established to predict the protein extractability under different conditions. These results suggest that a-amylase is more effective than cellulases in protein extraction from HDRB, and that a-amylase can release most of the water-soluble protein from HDRB.
Session 30C, Food Chemistry: Proteins
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