The Preparation And Functional Assessment Of The Digests Of ?-Casein From Bovine Milk

Cow's milk is rich in protein,casein of milk can produce bioactive peptides through digestion in vivo,and ?-casein,accounting for about 37% of the total protein of cow's milk,is one of the important nutrient components of casein in cow's milk.Recent studies have found that ?-casein has antioxidant,immune enhancement,and other physiological functions.In this study,bovine casein was digested in vitro,and the functional characteristics and antioxidant functions of digestive products of pepsin,trypsin and complex enzymes were evaluated under gastrointestinal digestive conditions.The main contents of this experiment are as follows:(1)Three kinds of pepsin digestive products,namely pepsin digestive products,trypsin digestive products and complex enzyme digestive products,were obtained by simulating in vitro gastric digestion(pepsin),intestinal digestion(trypsin)and gastrointestinal digestion(compound enzyme)of bovine lactose-casein in vitro.The result of three digestive hydrolysis curve found that the degree of hydrolysis of hydrolysis degree increased with the time,and the degree of hydrolysis of compound enzyme digestion products up to 14.45%±0.30%,degree of hydrolysis of trypsin digestion products was 7.36%±0.23%,and degree of hydrolysis of pepsin digestion products was 2.67%±0.15%.(2)The the structure and functionof the three digestive products was evaluated.The results of FTIR and SDS electrophoresis showed that the molecular weight of protein decreased from 24 kDa to 17 kDa,10 kDa of short peptides after enzymatic hydrolysis.The secondary structure was destroyed after digestive,?-helix content and ?-fold content decreased,surface hydrophobicity decreased.Compared with the undigested ?-casein,the solubility of the three ?-casein digested products increased in the range of pH 3-10,the emulsifying property and emulsifying stability of the three ?-casein digested products increased in the range of pH 3-10,water and oil absorption of the three ?-casein digested products decreased.(3)The hydroxyl radical scavenging,superoxide anion scavenging,DPPH scavenging and reducing ability of the three digestive products were evaluated in vitro.The results showed that compared with undigested ?-casein,pepsin digestion products,trypsin digestion products and compound enzyme digestion products all have significant hydroxyl radical scavenging ability,superoxide anion scavenging ability,DPPH scavenging ability and reducing ability(P < 0.05),and the antioxidant ability of digested products of compound enzyme was better than that of digested products of single enzyme.(4)The results of evaluate the antioxidant activity of continuous digestive products(i.e.compound enzyme digestive products)in vivo showed that compared with the model group,the compound enzyme digestive products could reduce the production of MDA in serum and liver of mice(P < 0.05),increase the activities of CAT(P < 0.05),SOD(P < 0.05)and GSH-Px in serum and liver of mice(P < 0.05).The results showed that the digestive products of ?-casein compound enzymes could enhance the activity of endogenous oxygen free radical scavenging enzymes,this study provided a theoretical basis for the development of functional food by its antioxidant stress in animals.Therefore,?-casein digested product by simulated gastrointestinal digestion,have good functional and antioxidant properties,it can provide a theoretical basis for the development of milk base products and health food products.