Abstract: The impact of secondary products from lipid oxidation on structure and functional characteristics of silver carp myofibrillar protein were studied by using malondialdehyde (MDA) oxidizing systems (0–1.00 mmol/L). The results showed that the contents of carbonyl and free amino groups content changed slightly with increasing MDA concentration from 0.05 to 0.50 mmol/L. The active thiol contents and surface hydrophobicity were enhanced as the malondiadehyde concentration was increased to 0.25 mmol/L, but dityrosine content decreased somewhat; Ca2+-ATPase activity initially decreased and then increased, whereas the opposite trend was observed for its solubility. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) indicated that oxidation promoted the crosslinking and aggregation of myofibrillar protein molecules mainly through disulfide bonds. The increasing MDA concentration resulted in a reduction in α-helix content and an increase in β-sheet content. The results implicate that in the proper concentration range, MDA as a representative of the secondary products of lipid oxidation led to mild oxidation of myofibrillar protein, and the mild oxidation of myofibrillar protein at MDA concentration of 0.25 mmol/L promoted partial unfolding of myofibrillar protein, resulting in exposure of more active sites and consequently protein cross-linking, which might contribute to the formation of surimi gel.

Key words: silver carp, myofibrillar protein, malondialdehyde, protein oxidation, mild oxidation