Tracking structural modifications and oxidative status of myofibrillar proteins from silver carp (Hypophthalmichthys molitrix) fillets treated by different stunning methods and in vitro oxidizing conditions.

In order to explain the increased susceptibility of stunning-stressed fillets to oxidative modifications, effect of stunning methods (percussion and gill cut) and in vitro metal-catalyzed oxidation on structural changes and oxidative status of myofibrillar proteins (MPs) from silver carp fillets was examined. In comparison to the percussion group, oxidized MPs (10 mM HO) from gill cut-stunned fillets exhibited higher extent of structural disintegration as well as elevated carbonyl levels. Using label-free proteomics, isoforms of myosin heavy chain and actin were major proteins underwent oxidative modifications including monooxidation of methionine, dioxidation of aromatic amino acids, adduction of lipid peroxidation products with aliphatic amino acids, and the carbonylation of lysine and arginine into semialdehydes. In addition, amino acids located at the tail portion of myosin were highly accessible to oxidation. Owing to the structural disorganization caused by stunning stress, MPs from gill cut-stunned fillets were more susceptible to oxidation in vitro.