In vitro antioxidant activity of papain-treated grass carp (Ctenopharyngodon idellus) protein hydrolysate and the preventive effect on fish mince system

Antioxidant activities of papain-treated grass carp protein hydrolysate (HP) were investigated using in vitro methods and in grass carp mince system. Lipid oxidation, colour changes and cooking loss in grass carp mince added with 0% (control), 0.5%, 1.0%, 2.0% and 4.0% HP during refrigerated storage (4 degrees C) for 8 days was studied. HP could chelate 50% of Fe2+ and scavenge 50% of hydroxyl radicals at the concentration of 0.81 and 8.12 mg mL-1, respectively. And HP could effectively decrease peroxide values and inhibit the formation of thiobarbituric acid reactive substances in fish mince throughout storage (P < 0.05), at the application level range from 0.5% to 4.0%. In HP-treated samples the formation of conjugate dienes (CDs) was retarded 530% at day 6 of storage compared to control. In addition, HP could significantly decrease cooking loss of fish mince samples, at the application level range from 1.0% to 4.0%.