Study And Application On The Technology Of Hydrolyzing Whey Protein Powder With Complex Enzyme And The Antioxidant Activity Of Hydrolyzed Product

Whey is by-product of industrial production of cheese and casein,which has high nutritional value.This thesis takes concentrated whey protein powder(WPC-80)as the research object,in order to improve the antioxidant activity of whey protein powder hydrolysate(WPPH),the whey protein powder was hydrolyzed by trypsin and bromelain,and the hydrolysate was made into lyophilized powder of enzymatic hydrolysate of whey protein(abbreviation:whey protein freeze-dried powder)by vacuum freeze-drying technology,which was applied to Mongolian traditional milk tea powder to improve the antioxidant activity of milk tea powder.The main research contents and results are as presented follows:(1)The technology of hydrolyzing whey protein powder with complex enzyme was optimized.With WPPH hydrolysis degree and antioxidant activity as indicators,two kinds of protease with better enzymolysis effect were selected from four kinds of protease.The influence of five factors on the enzymolysis effect of two kinds of protease was studied by single factor method.The optimum conditions of enzymatic hydrolysis of whey protein powder were determined by adding enzyme and L9(34)orthogonal test design,taking the degree of hydrolysis and antioxidant activity of WPPH as the index.(2)Analysis of nutritional components and antioxidant activity of whey protein freeze-dried powder.The whey protein powder enzymatic hydrolysate was liquid.In order to facilitate the application,the enzymatic hydrolysate was vacuum freeze-dried to powder.The nutritional composition,antioxidant activity and stability of whey protein lyophilized powder were analyzed.Dilute whey protein lyophilized powder with deionized water to a certain concentration and place it in a water bath pot.The temperature was set at 4?,25?,40?,60?,80?,the antioxidant activity was measured after 0 min,30 min,60 min,90 min,120 min and 150 min.The results showed that high temperature,extreme acid and alkaline conditions will cause whey protein lyophilized powder to lose some antioxidant activity.The antioxidant activity was stable at pH6.0 and at 4-40?.(3)Study on the application of whey protein freeze-dried powder in the production of milk tea powder.Adding 0.02%(W/W)whey protein freeze-dried powder to milk tea powder could obviously improve the antioxidant activity of milk tea powder,in which DPPH free radical clearance increased by 33.34%,hydroxyl free radical clearance increased by 35.72%,and total antioxidant capacity increased by 16.90 ?mol/L.Within 50 days of storage,the DPPH free radical scavenging rate of milk tea powder decreased by 4.75%,the hydroxyl free radical scavenging rate decreased by 4.38%,the total antioxidant capacity decreased by 3.69?mol/L,and the solubility remained basically the same.It was confirmed that the hydrolysate of whey protein powder which was hydrolyzed by trypsin and bromelain,had strong antioxidant activity.The antioxidant activity of the freeze-dried whey protein powder was stable at pH6.0 and at 4-40?.Adding it to the traditional Mongolian milk tea powder can significantly improve the antioxidant activity of the milk tea powder,which provides the theoretical basis and technical basis for the subsequent application of the enzymolysis products of whey protein powder in food.