Study On The Improvement In Functionalities And Prodution Of ACE Inhibitory Peptides From Wheat Gluten By Enzymatic Hydrolysis

Wheat gluten is a kind of cheap and superior quality protein resources. But the presence of hydrophobic amino acids leads to low solubility, and its application is limited. So it is a very significant job to enhance the functionality by the enzymatic modification of wheat gluten. Meanwhile, ACE inhibitory peptides with high inhibiting activity were prepared for wheat gluten hydrolysis and two isolated component was concentrated. The main research contents were as follow:(1) Compare with other pretreatment methods, alkaline pretreatment was preferred. The optimal processing conditions were 0.4 mol/L of NaOH, the ratio 1:2 of NaOH solution and wheat gluten suspension,60 min of pretreatment time at 60℃. According to the effect of hydrolysis degree on the solubility and emulsifying properties, the average of EAI and ES was defined to be the composite index of modification on wheat gluten.(2) Protamex was found to be the best proteolytic enzyme by comparing the relation between the degree of hydrolysis and solubility. The orthogonal experiments showed that the optimum condition are: substrate concentration 60mg/ml, enzyme concentration 1100U/g, pH 7.5, temperature 35℃, reaction time 3 h. At this condition, the solubility can reach 22.7%, emulsion ability and emulsion stability can reach 92.8% and 87.65%.(3) Wheat gluten was hydrolyzed by Alcalase, Protamex and Flavourzyme respectively under their optimal condition. The best protease Flavourzyme was screened out for ACEIP's preparation by the comparation of hydrolysis process and hydrolysate's inhibiting activity. 3 hours later, the hydrolysate's inhibiting activity reached the highest level with the inhibition rate of 52.5%.(4) The molecular weights of hydrolysates from wheat gluten were determined by SDS-polyacrylamide gel electrophoresis(SDS-PAGE). All the molecular weights are below 19 kDa, which indicates that the hydrolysates from wheat gluten are polypeptides and the molecular weights effect on the ACE inhibiting activity. Wheat-gluten-drived ACE inhibitory peptides remained activity under various temperature and pH treatments.(5) The enzymatic hydrolysate was concentrated by ultra-filtration membrane with molecular weight cut-off 10 kDa and 5 kDa respectively. The results shows that the ACE inhibiting activity of enzymatic hydrolysate increased from 52.5% to 62.4%, and IC50 decreased from 1.73 mg/ml to 0.44 mg/ml. And two isolated component from ACE inhibitory peptides was analysed by RP-HPLC.