Effect of lipoxygenase-catalyzed linoleic acid oxidation on structural and rheological properties of silver carp (Hypophthalmichthys molitrix) myofibrillar protein

The goal of this study was to investigate the effects of protein oxidation on myofibrillar protein (MP) gel structure and rheological properties using a lipoxygenase-linoleic acid system. The results showed that the addition of the linoleic acid significantly increased the protein carbonyl and dityrosine content (P < 0.05), whereas the contents of sulfhydryl and the free amino groups were increased first and then decreased. Circular dichroism spectra and surface hydrophobicity studies evidenced that the disruption of alpha-helix conformation and the exposure of hydrophobic sites were induced by oxidized linoleic acid (OLA). Results of SDS-PAGE indicated that non-disulfide covalent linkages were implicated in the formation of cross-linking in myofibrillar proteins induced by OLA. The rheological tests revealed that the storage modulus (G') of OLA moderate oxidative modification (<= 2.5 mmol/L) significantly increased, whereas the storage modulus (G') of OLA excessive oxidative modification (> 2.5 mmol/L) significantly decreased. Moreover, microstructure analysis indicated the presence of more compact threedimensional network structures in moderate oxidative modification MP than the controls. It was concluded that moderate oxidative modification improved the gel-forming ability of MP. This result can provide a theoretical basis for producing higher quality products in surimi processing industry.