Preparation Of Bioactive Peptides From Wheat Bran Protein And Its Comprehensive Utilization

Wheat bran(WB)is a main by-product in the process of wheat starch production.It is mainly used for animal feed and a little is made into high-fiber foods or used as a culture medium for edible fungi.Further processing and re-using is barely taken.Component analysis showed that WB contained 16.12%protein,15.33%starch,24.55%hemicellulose,7.79%cellulose,8.25%lignin,5.52%ash and 2.55%fat.If deep processing can be done,WB can both bring considerable economic benefits to food industry and balance diet which can help improve human health.This paper mainly studied the extraction and hydrolyzation of wheat bran protein(WBP),and analysed the antioxidant properties,moisture absorption and moisturizing properties of wheat bran polypeptide.The yield,purity and secondary structure of WBP obtained by conventional alkali extraction(AE),microwave-assisted extraction(MAE)and ultrasound-assisted extraction(UAE)were compared.The results indicated that UAE method is more conducive to protein extraction.To improve the yield of WBP,RSM was used to optimiz the extraction process.The calculated optimum process condition was as follow:temperature 45 ~oC,liquid-solid ratio 19;KOH concentration 0.02 mol/L and ultrasound time 1 h.Under this condition,the purity of extracted protein was 75.99%,and a maximal yield of 68.04%was reached.Commercial proteases were used to hydrolyze WBP,this research determined an optimum process conditions for enzymatic WBP hydrolysis by single factor test and Plackett-Burman test design combined with the Box-Behnken response surface optimization.The best conditions were as follow:substrate percentage 2%,enzyme dosage10000 U/g,flavor enzyme and alkaline enzyme ratio 1:2,temperature 50°C,pH 8.0 and time 5 h.The hydrolysis degree of wheat bran polypeptide obtained under optimum conditions was 26.24%and the reducing power of the enzyme digested solution diluted 10-fold was 0.53.The application of wheat bran polypeptide was studied.The results showed that scavenging rates of ABTS and hydroxyl radicals improved continuously with increasing concentration of the wheat bran polypeptide and Vc solution that could also effectively inhibit lipid oxidation.Wheat bran polypeptide had a certain moisture absorption and retention ability.In medium humidity environment,the moisture absorption rate of wheat bran polypeptide reached its maximum at 60 h,and then stayed constant;the test of moisture retention results showed that the moisture retention rate of wheat bran polypeptide was stable after 12 h,indicating that the wheat bran polypeptide had good moisture absorption and moisturizing properties.