Abstract: In this paper, myofibrillar protein from grass carp was artificially oxidized in hydroxyl radical-generating system with H2O2 concentrations of 0.1, 1.0, 5.0 and 10.0 mmol/L, and the effect of oxidization on the structural characteristics and gel properties of myofibrillar protein was investigated. The results showed that the carbonyl content increased significantly (P < 0.05) after oxidization by 111.35% compared to the initial value when the concentration of H2O2 was 10.0 mmol/L. With the increase in H2O2 concentration, the total thiol group level, free thiol group level, and free amine content decreased significantly (P < 0.05), while bityrosine content and surface hydrophobicity increased significantly (P < 0.05). The sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) result showed that hydroxyl radical oxidation could induce the crosslinking and aggregation of protein molecules, thereby forming aggregates with molecular mass higher than 200 ku. The above results indicated that the thiol group, tyrosine and tryptophane residues of myofibrillar protein were modified after hydroxyl radical oxidation, thus leading to a significant change in protein structure. In addition, the gel properties of myofibrillar protein were also influenced by oxidation, the network structure of the gel was damaged, and the portable water in the gel was converted to free water. These changes finally induced apparent decreases in the gel strength and water-holding capacity.

Key words: grass carp (Ctenopharyngodon idellus), myofibrillar protein, protein oxidation, structural characteristics, gel properties