Optimization of Antioxidant Hydrolysate Produced from Tibetan Egg White with Papain and Its Application in Yak Milk Yogurt

The objective of the present study was to produce antioxidant hydrolysate from Tibetan egg white protein hydrolyzed with papain, and to investigate the effect of added papain egg white hydrolysate (PEWH) on the quality characteristics and amino acid profiles of yak milk yogurt. A response surface methodology (RSM) was utilized to analyze the effects of hydrolysis time (X(1)), the ratio of enzymes to substrates, and enzyme dosage (X(3)) on the superoxide anion radical (O(2)(−)) scavenging activity of hydrolysates. The predicted maximum value of O(2)(−) scavenging activity (89.06%) was obtained an X(1) of 2.51 h, X(2) of 4.13%, and X(3) of 4500 U/g of substrate, almost approaching the experimental value (88.05 ± 1.2%). Furthermore, it was found that the addition of PEWH to yak milk can enhance acidification, sensory score, the number of lactic acid bacteria (LAB), and the amino acid content in yak milk yogurt. The results suggested that PEWH displayed an exceptional potential to be developed as a functional food ingredient that could be applied during the manufacturing process of yak milk yogurt.