OPTIMIZATION OF LIMITED HYDROLYSIS OF PROTEINS IN RICE RESIDUE AND CHARACTERIZATION OF THE FUNCTIONAL PROPERTIES OF THE PRODUCTS.

ABSTRACT Four enzymes, alcalase, neutrase, bromelain and papain, were used individually to hydrolyze proteins in rice residue. The process conditions were optimized by response surface methodology (RSM). Under optimal conditions hydrolyzate yields generated with neutrase, alcalase, bromelain and papain were 49.3, 56.7, 30.8 and 16.6%, respectively. Molecular weight distributions of the hydrolyzates were analyzed by high-performance liquid chromatography. The results showed that hydrolyzate generated with neutrase and alcalase had smaller polypeptides than those with bromelain and papain. Compared with alkaline extraction, the solubility of the hydrolyzates treated by enzyme was greatly improved. Antioxidant activities of the hydrolyzates were also evaluated in this study. The induction time of the hydrolyzate generated with alcalase was longer than those with other enzymes. Emulsifying activities of the hydrolyzates generated with different enzymes were significantly different and that prepared with alcalase exhibited the best emulsifying activity among all other hydrolyzates. PRACTICAL APPLICATIONS Rice residue is a by-product of extracting starch and other carbohydrates from rice. The residue is rich in protein, but is normally used as animal feed because of the poor solubility. In this research, alcalase, neutrase, bromelain and papain were used individually to hydrolyze proteins in rice residue. RSM was used to establish models to estimate the optimum conditions and predict the hydrolyzate yield at different conditions. Under the optimum conditions, hydrolyzates were prepared and the functional properties of the products generated with different enzymes and extracted by alkaline were compared. The solubility and other properties of rice protein hydrolyzates were greatly improved, so it could be used for nutritional supplementing, functional enhancement, etc. Therefore, this article has practical value, which provided the theoretical basis for the application of rice residue. This text should highlight the uses of rice residue, either actual or potential. [ABSTRACT FROM AUTHOR]