Whey and soy protein hydrolysates inhibit lipid oxidation in cooked pork patties

Pork patties containing 1.5% NaCl and 2% hydrolyzed whey protein isolate (WPI, 1 h with flavourzyme or 6 h with protamex) or soy protein isolate (SPI, 0.5 h with chymotrypsin or flavourzyme) were cooked to 70 °C and subsequently stored at 4 °C up to 7 days. Lipid oxidation in patties during storage was analyzed by measuring the concentration of conjugated dienes (CD) and thiobarbituric acid-reactive substances (TEARS). Intact WPI and SPI, and their hydrolysates, were all inhibitory of oxidation (P<0.05) in cooked patties, with SPI being slightly more effective than WPI. Hydrolysis with protamex augmented the antioxidative activity (CD, TBARS) of WPI. Hydrolysis with either chymotrypsin or flavourzyme improved the ability of SPI to retard CD formation but did not delay the production of TBARS in stored pork patties.