Research On Antioxidant Activity And Application Of Donkey Whey Proteolytic Peptide

In this experiment,donkey whey protein was used as a raw material to prepare whey proteolytic peptides,to evaluate its in vitro antioxidant activity and to explore its stability,and to develop an antioxidant enzyme hydrolysed peptide beverage.The specific experimental conclusions are as follows:(1)Response surface methodology(RSM)was used to optimize the enzymatic hydrolysis conditions,and the optimal conditions were as follows:substrate concentration was 4%,enzymatic hydrolysis time was 4 h,temperature was 39?,p H was 8,and enzymatic base ratio was 4%,under which the maximum DPPH free radical scavenging rate of 10 mg/m L donkey whey proteolytic peptides could reach 45.5%.(2)The antioxidant activity of the peptides in vitro was evaluated by a variety of antioxidant experiments.The results showed that the antioxidant activity of peptides was higher than that of original whey proteins at 10 mg/m L.The scavenging rates of DPPH free radicals,hydroxyl free radicals,ABTS free radicals,and superoxide anions were 45.24%,42.43%,65.45% and 53.79%,respectively,and the iron reduction capacity was 0.46.In addition,the anti-aging experiment results showed that the survival rate of Saccharomyces cerevisiae cells in the enzymatic hydrolysate group(the concentration of enzymatic hydrolysate was 1,2,4 mg/m L)was higher than that in the blank group when the cell time series life reached the 6th day,indicating that the enzymatic hydrolysate group could effectively delay the aging of yeast cells.(3)Ultrafiltration and dextran gel column chromatography were used to isolate and purify the enzymatic hydrolyzed peptides,and the antioxidant activity of the peptides was improved.Then,the components with strong activity after chromatography were identified by mass spectrometry.According to the Byonic software and the structural characteristics of antioxidant active peptides,seven active peptides were further screened out.The sequences were ASDISLL,PAVF,EGNLEII,EDPAVFTVN,LHASAK,KSPFVIY and VYSTRIIF,respectively.The antioxidant activity of the peptides was verified by solid-phase synthesis.The antioxidant activities of PAVF and KSPFVIY peptides were increased by 1.29 and 1.73 times,respectively,compared with those of the chromatographic components.(4)The stability experiment of peptides showed that it had good thermal stability and gastrointestinal digestive ability,but the antioxidant activity changed greatly under the influence of environmental p H.Based on the stability experiment results,a peptide drink was developed with enzymatic hydrolyzed peptides as the raw material.Through orthogonal experiment,?-cyclodextrin(1.5%),granulated sugar(6%),citric acid(0.15%)and enzymatic hydrolyzed peptides(2.5%)were obtained.The highest DPPH radical scavenging rate and the lowest centrifugal precipitation rate were 64.76% and 0.08%,respectively.