A two-step enzymatic modification method to reduce immuno-reactivity of milk proteins

A two-step enzymatic approach to reduce immuno-reactivity of whey protein isolate and casein has been studied. The method involves partial hydrolysis of proteins with proteases, followed by repolymerization with microbial transglutaminase. Whey protein isolate partially hydrolyzed with chymotrypsin, trypsin, or thermolysin retained about 80%, 30%, and 20% of the original immuno-reactivity, respectively. Upon repolymerization the immuno-reactivity decreased to 45%, 35%, and 5%, respectively. The immuno-reactivity of hydrolyzed and repolymerized casein was negligible compared to native casein. The repolymerized products were partially resistant to in vitro digestion. Peptides released during digestion of repolymerized thermolysin-whey protein hydrolysate had less than 5% immuno-reactivity, whereas those of whey protein control exhibited a sinusoidal immuno-reactivity ranging from 5 to 20%. Peptides released during digestion of repolymerized thermolysin-casein hydrolysates had no immuno-reactivity. These results indicated that it is possible to produce hypoallergenic milk protein products using the two-step enzymatic modification method involving thermolysin and transglutaminase.