Study on Preparation and Antioxidant Activity of Hydrolysate from Neutral Protease in Walnut Protein

[Objective] The study was to research the optimum process condition on preparing hydrolysate from walnut protein and the antioxidant activity of the hydrolysate.[Method] With the walnut protein as the substrate,the orthogonal test was taken to study the process conditions on preparing hydrolysate from walnut protein,and the antioxidant activity of the enzymatic hydrolysate was studied through detecting its scavenging activity on free radical.[Result] The optimum process condition on preparing hydrolysate from walnut protein was temperature of 40 ℃,substrate concn.of 4%,enzyme concn.of 4 000 U/g,pH value of 8.0.The hydrolysis degree of the hydrolysate from walnut protease was related to its scavenging activity on hydroxyl free radical(OH·)and superoxide anion free radical(O2·),and when its hydrolysis degree was 24.2%,its scavenging rates on hydroxyl free radical(OH·)and superoxide anion free radical(O2·) were 17.0% and 52.0% resp.[Conclusion] The hydrolysate which hydrolysis degree was 24.2% was separated by Sephdex G-25 gel filtration chromatography,and then 4 kinds of peptide mixtures A,B,C and D were obtained,in which the scavenging activity on free radical of peptide mixture C was the biggest,and that of peptide mixture D was the smallest.