Abstract: 【Objective】The conditions of composite enzymatic hydrolysis of defatted rice bran were established in order to give some technical guidance for the high value utilization of defatted rice bran , and the nutritive characteristic change of its enzymatic extract was evaluated.【Method】 In order to prepare a high nutritional value enzymatic extract, defatted rice bran was used as the raw materials, they were firstly treated by gelatinization and liquidation, and then was simultaneously hydrolyzed by the composite enzyme (glucoamylase, acid cellulose, and acid protease). The reduced sugar yield and protein extraction yield were chosen as the evaluation criteria, as there are differences among parameters for reduced sugar yield and protein extraction yield, a fuzzy comprehensive evaluation model was established to optimize the parameters for the composite enzymatic hydrolysis of defatted rice bran. Freeze drying method was used to prepare the hot water extracts and the enzymatic hydrolysate extracts. The contents of solid, carbohydrate, soluble fiber and protein in defatted rice bran were also determined by using the government standard methods. The efficiency of composite enzymatic hydrolysis was evaluated by the nutriment differences compared by the hot water extraction and composite enzymatic hydrolysis. Amino acids contents of the three preparations were measured by high-speed amino acid analyzer. Nutritive evaluation for the three preparations’ proteins was assessed by using the WHO/FAO method.【Result】The optimum conditions for composite enzymatic hydrolysis established by fuzzy comprehensive evaluation model were that the composite enzyme concentration was 3.5%, glucoamylase was 0.5%, acid cellulose was 1.5% and acid protease was 1.5%, the composite enzymatic hydrolysis was carried out at pH 4.1, temperature 57.4℃, material to water ratio 1:5, and 190 minutes. The raw material utilization ratio, carbohydrate conversion ratio, soluble dietary fiber extraction yield and protein extraction yield by the composite enzymatic hydrolysis were 48.43%, 65.33%, 6.68% and 58.43%, the percentage of essential amino-acid in the composite enzymatic extract protein was 36.93%. Compared with the hot water extracting, the raw material utilization ratio, carbohydrate conversion ratio, soluble dietary fiber extraction yield and protein extraction yield was increased by 118.73%, 90.74%, 284.22% and 257.14% as compared with those of hot water extracting, the percentage of essential amino-acid increased by 276.33% (P＜0.05). Compared with the raw material, the soluble dietary fiber increased by 13.62%, the content of essential amid acid in per solid increased by 14.78%, which of the lysine, methionine, threonine and valine increased by 35.38%, 37.75%, 40.06% and 7.70%, respectively (P＜0.05), the ratio of essential amino acid to nonessential amino acid was 0.59, which was closely to the FAO/WHO recommended value 0.6. 【Conclusion】The raw material utilization ratio increased significantly through the composite enzymatic hydrolysis process, compared to the hot water extracting, the soluble solid content, soluble carbohydrate, soluble dietary fiber and protein content raised significantly, thus it has provided a dependable approach for preparation of a defatted rice bran enzymatic extract with potential use as a functional food.

Key words: defatted rice bran, composite enzymatic hydrolysis, reduced sugar yield, protein extraction yield, nutritional properties