Studies On The Extraction And Hydrolyzion Using Immobilied Protease Of Rice Dregs Proteins

Rice protein is recognized the high quality frumentaceous protein, which has some characters, such as reasonable amino acid compositions, low hypoallergenic character. It is very suitable for infants and babies and other special crowds as nutritious food. Most people at home and abroad have attached importance to the rice protein research and development of product. This paper mainly studied on the extraction of rice dregs and rice dregs hydrolyzed by Immobilized alkaline protease.The study of extraction of rice dregs use water by a single factor experiment for extract time, temperature, the ratio of raw material to water and wash time. The extract time, temperature, the ratio of raw material to water were optimized by orthogonal experiment, the highest protein extraction is 71.83% at temperature 80℃, time 1.5h, the ratio of raw material to water 1:10, wash one time.Rice dregs were extracted by alkali solution, the temperature, the concentration of alkali solution, extraction time, the ratio of raw material to water were studied by a single factor experiment. The concentration of alkali solution, extraction time and the ratio of raw material to water were optimized by response surface method. The relation between threes factors and protein extraction was fitted by means of multiple quadratic regression equation. The experimental optimum condition of extraction time 2.2h, the concentration of alkali solution is 0.288%, the ratio of raw material to water is 1:11, temperature 50℃, under these conditions, and the rice dregs protein extraction would reached 72.50% in theory, 70.49% was received at laboratory. The experiment approved that the results were consistent with the predicted values.Alkaline protease was immobilized by using sodium alginate as carrier, glutaraldehyde as cross-linking agent. The concentrations of sodium alginate, alkaline protease, CaCl2, glutaraldehyde and cross-linking time were studied by a singe factor experiment. Use response surface method found better method: the concentrations of sodium alginate, alkaline protease, CaCl2, glutaraldehyde were 2.5%, 3mg/ml, 2%, 4% respectively, the recycling rate of activity reached 61.48% in theory, 58.34% was received at laboratory. The optimum temperature of immobilized alkaline protease is 60℃, the optimum pH is 9.Alkaline protease was immobilized by using sodium alginate as carrier, glutaraldehyde as cross-linking agent. The immobilized-alkaline hydrolyzed rice dregs were studied by a single factor experiment. The hydrolysis time, [E]/[S] and pH were optimized by response surface method. The relation between three factors and hydrolysis degree was fitted by means of multiple quadratic regression equation. The experimental optimum condition of hydrolysis time 2h, [E]/[S] is 1:9, pH8.9, temperature is 60℃. The experiment approved that the results were consistent with the predicted values, hydrolysis degree up to 19.04% in theory, 17.74% was received at laboratory.The study of processing characteristics of rice dregs peptide showed that the rice dregs peptide had a good solubility and could keep the high NSI over 75.00% at the pH of 2-10. Compared with rice dregs protein, rice dregs protein peptide had a good emulsification and emulsion stability, but had a bad ilo and water absorption.