Abstract: The goal of this research was to explore the antioxidant effect of α-tocopherol on lipid-protein systems from crab muscles. Changes in the sulfhydryl content, surface hydrophobicity, secondary structure and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) profile of myofibrillar protein from the model systems were examined during storage at room temperature. The results showed that after oxidation for 12 and 24 h, fatty acid composition of crab lipids changed; a significant decrease was observed in the content of unsaturated fatty acids. The sulfhydryl content of crab muscles mixed with 24 h oxidized crab lipids decreased and the surface hydrophobicity significantly decreased; as the degree of oxidation increased, the contents of α-helix and β-sheet decreased, while β-turn content increased. Compared with the control group, the addition of α-tocopherol displayed a lower sulfhydryl content and a significantly slower rate of increase in the surface hydrophobicity, as well as an increase in α-helix and β-sheet and a decrease in β-turn. SDS-PAGE showed the inhibitory activity of the antioxidant against the degradation of myofibrillar protein. Optical density analysis using Gel Image System software showed that a significant difference existed between only a few bands, indicating that SDS-PAGE was a less sensitive tool than sulfhydryl content and surface hydrophobicity for evaluating the protein oxidation. The results in this study indicated that oxidized crab lipids could accelerate protein denaturation and the effect was dependent on the degree of oxidization; α-tocopherol had significant inhibitory activity against the consequent protein oxidation.

Key words: α-tocopherol, myofibrillar protein, lipid, oxidation