LAUSR

Abstract The study investigated effects of gallic acid (GA, 0, 1, 5, 25 and 125 μmol/g) on properties of oxidatively stressed Japanese seerfish myofibrillar protein (MFP). Results showed that GA alleviated carbonyls formation and protected free amine. 5 μmol/g GA stabilized sulphydryls and secondary structure while 125 μmol/g GA enabled great loss of sulphydryls and reduced α-helix structure. Analysis of tryptophan fluorescence and surface hydrophobicity indicated that GA induced the unfolding of MFP structure but not in a dose-response fashion. Polymers were formed along with marked attenuation of myosin heavy chain in MFP with 125 μmol/g GA, and its particle size was the largest. Compared with purely oxidized MFP, MFP with 125 μmol/g GA showed a radical peak with narrower peak width but higher intensity. Results imply that high dose GA formed thiol-quinone adducts, enhancing polymerization. It also formed stable protein-bound phenoxyl radicals, inhibiting protein oxidation. Compared with non-oxidized group, storage modulus of MFP with 5 μmol/g GA increased sharply but that of MFP with 125 μmol/g GA decreased distinctly. The study suggests the role of GA on MFP depends much on its dose. Low dose GA could be used for improving fish MFP gelling property.