Abstract:

Whey protein was hydrolyzed in different ways, the antibacterial ability and the degree of hydrolysis of
hydrolysates were measured, and their correlation was studied. The results showed that hydrolysates of whey protein at a
certain degree of hydrolysis had a significant antibacterial ability. The antibacterial ability of hydrolysates was closely related
to the degree of hydrolysis (r = 0.9740 when hydrolysis degree was less than 12 mg free amino acids/mL; r=－0.9468 when
hydrolysis degree was higher than 12 mg of free amino acids/mL). An optimal degree of hydrolysis was found under different
hydrolysis conditions when whey protein was hydrolyzed by trypsase. At this optimal degree of hydrolysis (10—12 mg of free
amino acids/mL), the hydrolysates of whey protein showed the highest antimicrobial activity. Hydrolysates prepared by
hydrochloric acid showed significantly lower antibacterial capacity and poorer stability when compared to those prepared
by trypsase. In summary, this study demonstrated that appropriate hydrolysis could significantly improve the antimicrobial
capacity of whey protein hydrolysates. The optimum hydrolysis degree was in the range of 10—12 mg of free amino acids/mL.
Whey protein could potentially be used for the development of new natural food preservatives.

Key words: whey protein, trypsase, degree of hydrolysis, antibacterial capability