Study On The Separation Of A-Casein And β-Casein From Yak Casein And Nutritional Evaluation Of β-Casein Formula Powder

Bovine milk is a kind of digestive natural food containing abundant nutrition and consisted proportionally. However, there are some differences between the protein of human and bovine milk such as the protein content and composition. Just these differences lead to the bovine milk protein worse digestion than human milk protein. The objectives of this study are to investigate the technology of selectively separating α-casein and β-casein from yak casein, base on the difference between bovine milk and human milk in casein. The clotting behavior and degestion in vitro are compared further. Finally, the PER of β-casein rich formula powder and ordinary formula powder were determined.The results of SDS-PAGE indicated that when the content of Resolution agent and Complexing agent are 3.0M and 0.01M respectively, can get a-casein rich fraction contained a-casein about 74.2% and β-casein rich fraction contained β-casein about 75.% with the rate of yield was 69.5% and 26.5% respectively.Than based on the acid coagulation experiment, it was found that the large hard clots of a-casein rich fraction was formed however the loose clots of β-casein fraction at 37 ℃, pH4.0. Pepsin digestibility of the casein fractions followed the order β-casein > α-casein > bovine casein. The results of feeding test indicated that the PER of β-casein rich formula powder is better than ordinary formula powder and the β-casein fraction may be used for infant feeding.Finally, the industrial technology of selectively removal of β-lactoglobulin from whey proteins was studied using protease hydrolysis and ion-exchange resin methods. The results indicated that three protease can not hydrolyze β-lactoglobulin uniquely but all the component of whey protein. However, the content of β-lactoglobulin in hydrolysate which hydrolyzed by protease M was higher. Therefore protease M can be used to produce β-lactoglobulin from whey protein. SDS-PAGE results showed that a decrease in the content of p-lactoglobulin from 39.7% to 16.0% after ion-exchange resin treatment.