Abstract:
This research was aimed to study the conditions for extraction of soluble proteins from broken rice, rice bran and defatted rice bran by using enzymatic treatment. The selection of enzyme for each treatment was based on the structure of raw materials. The alpha-amylase and protease were chosen for the extraction of soluble proteins from broken rice. Whilst alpha-amylase, cellulase, mixed enzymes (arabanase, cellulase, hemicellulase, beta-glucanase and xylanase), and protease were used for the extraction of soluble proteins from rice bran and defatted rice bran. It was found that the optimum condition for the extraction of soluble proteins from broken rice was obtained by using broken rice flour treated at 95 degree celcius for 30 minutes coupled with the addition of alpha-amylase (0.15% v/w), pH 6.5, incubating at 70 degree celcius for 120 minutes, resulting in 5.73 mg proteins/g broken rice in supernatants. The optimum conditions for extraction of soluble proteins from rice bran and defatted rice bran were obtained by digesting each raw material with mixed enzymes (0.10% v/w), pH 3.8, incubating at 50 degree celcius for 120 minutes for rice bran and for 60 minutes for defatted rice bran.The extracted soluble proteins obtained from rice bran and defatted rice bran was 60.90 and 31.70 mg proteins/g sample, respectively. The soluble proteins from broken rice, rice bran, and defatted rice bran were investigated for allergenic related protein, nutritional properties, and functional properties.The major allergenic protein reported by many researchs was the 16 kDa protein. The extract soluble proteins were analyzed by SDS-PAGE and gel filtration chromatography. There was no 16 kDa protein found. The nutritional quality of three extract proteins were compared with that of egg and casein. It was found that lysine, methionine, and phenylalanine were the limiting amino acids for protein from broken rice, rice bran and defatted rice bran, respectively. The extract protein from bran showed highest Protein Efficiency Ratio (PER) at 2.14 (C-PER) and 2.07 (DC-PER). The best foaming ability of protein solution among three extrated protein was found to be protein from rice bran. The rice bran soluble protein produced 18.00 ml. of foam from 50 ml. (0.20% w/v) protein solution. The emulsion ability of soluble protein from from rice bran and defatted rice bran were found to be the same, 0.55 and 0.58, respectively while that of the protein from broken rice was 0.36.