Prevention of protein and lipid oxidation in freeze-thawed bighead carp (Hypophthalmichthys nobilis) fillets using silver carp (Hypophthalmichthys molitrix) fin hydrolysates

Conversion of aquatic by-products into value-added food ingredients has gained great interest worldwide, and enzymatic hydrolysis is one of the most accepted methods for the recovery of by-product proteins. In our study, fins from silver carp (Hypophthalmichthys molitrbc) were hydrolyzed by four enzymes (trypsin, alcalase, papain, and neutrase) and the antioxidant activity of the derived fin hydrolysates was evaluated both in vitro and in freeze-thawed bighead carp (Hypophthalmichthys nobilis) fillets. The results showed that fin hydrolysates by trypsin and alcalase exhibited strong in vitro scavenging activity against 2, 2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals and chelating activity to ferrous ions. Freeze-thaw-induced protein oxidation (the formation of carbonyls and disulfide bonds) and degradation (the loss of Ca2+-ATPase activity) were significantly (P < 0.05) inhibited by fin hydrolysates. In addition, fin hydrolysates reduced lipid oxidation as evidenced by decreased free fatty acid content, peroxide value, thiobarbituric acid reactive substances (TBARS), and fluorescent compounds after multiple freeze-thaw cycles. Therefore, fin hydrolysates by trypsin and alcalase could be potential natural antioxidants in preservation of fish fillets.