Protective Effect and Mechanism of Tea Polyphenols on the Stability of Myofibrillar Protein in Oyster Treated by Freeze-thaw Cycle

The aim of this study was to investigate the effects of different concentrations of tea polyphenols (0.4%, 0.6%, 0.8%) on the water holding capacity and texture of oysters during freeze-thaw cycles, and to analyze the changes in the carbonyl and sulfhydryl content, structure and composition of myofibrillar proteins by using three spectroscopic techniques and SDS-PAGE, in order to elucidate the mechanism of the antifreeze protection of oysters by tea polyphenols in freeze-thaw cycle. The results showed that the addition of tea polyphenols could slow down the decrease of water holding capacity and texture deterioration of oysters, reduce the increase of carbonyl content and the decrease of sulfhydryl content and fluorescence intensity of myofibrillar protein, and delay the change of protein internal structure as well as the degradation of macromolecular protein. After seven freeze-thaw cycles, compared with the control group, the thawing loss, steaming loss and centrifugal loss of the 0.8% tea polyphenols treatment group decreased by 9.08%, 7.79% and 30.73% respectively, and the hardness, springiness and chewiness increased significantly (P<0.05). The carbonyl content of myofibrillar protein decreased by 14.59% (P<0.05), while the sulfhydryl content increased by 19.86% (P<0.05), and the secondary and tertiary structures were more stable. Therefore, tea polyphenols can effectively control the quality deterioration of oysters during freeze-thaw cycle by reducing the oxidative denaturation of myofibrillar protein.