Tea Polyphenols Affect Oxidative Modification and Solution Stability of Myofibrillar Protein from Grass Carp (Ctenopharyngodon idellus)

This study investigated the effects of different concentrations (0, 5, 10, 20, 50, and 100 μmol/g protein) of tea polyphenols (TP) on the oxidative modification and the physicochemical, structural, and gelling properties of myofibrillar protein (MP) from grass carp (Ctenopharyngodon idellus) oxidized by a hydroxyl radical-generating system. The results showed that low concentrations (5 and 10 μmol/g protein) of TP could effectively inhibit the formation of carbonyl groups and dityrosine, the loss of sulfhydryl groups and α-helix conformation, and the change of the tertiary structure of MP caused by hydroxyl radicals. Moreover, the presence of TP in all concentrations decreased the surface hydrophobicity of MP. TP at 10 μmol/g protein had better effects on preventing the oxidation-induced cross-linking and aggregation of myosin heavy chain (MHC) and actin of MP, keeping the stability of MP solutions with lower turbiscan stability index (TSI) values, and improving gelling properties characterized by higher hardness and gel strength of MP gels. By contrast, excessive presence of TP (20, 50, and 100 μmol/g protein) showed pro-oxidative effects on oxidatively stressed MP, which was detrimental to the MP and contributed to the denaturation and irregular aggregation of MP, the loss of MP solution stability, and lower gelling capacity with poor texture and gel strength. The concentration-dependent effects of TP on MP depended on the extent of MP oxidative modification and MP-TP interactions, indicating that a proper amount of TP has the potential to protect MP from oxidation and to enhance the gelling capacity of surimi during processing.