Effects of Composite Coatings on the Physicochemical Properties of Myofibrillar Protein and the Cooked Quality of Tilapia Fillets during Refrigeration

This study explored the impact of tea polyphenol-chitosan (T-Ch) and tea polyphenol-sodium alginate (T-SA) composite coatings on the quality of refrigerated tilapia fillets during storage at 4 ℃. The research focused on the changes in myofibrillar protein (MP) physicochemical properties, such as solubility, turbidity, total and active thiol groups, Ca²⁺-ATPase activity, and surface hydrophobicity and the effects on cooked fish quality, including infrared spectroscopy, gel strength, texture, in vitro digestibility, and sensory assessment, over storage periods of 0, 2, 4, 6, and 8 d. The findings demonstrated that both coatings effectively mitigated the extent of reductions in MP solubility, total and active sulfhydryl content, and Ca²⁺-ATPase activity, while also decreased the extent of increases in MP turbidity and surface hydrophobicity in refrigerated fish fillets. These slowed down the denaturation and aggregation of MP in refrigerated fish fillets, thereby enhancing their overall quality. Notably, the T-Ch treatment showed superior maintenance of MP solubility, active sulfhydryl levels, surface hydrophobicity, and Ca²⁺-ATPase activity compared to the T-SA treatment. Conversely, the T-SA treatment was more effective in preserving the total sulfhydryl content of MP. Although the coating treatment reduced the digestibility of the cooked fish after refrigeration, it increased the hydrophobic interactions and disulfide bond content of the fish myofibrillar protein (MP), thereby enhancing the gel characteristics of the fish and improving its sensory attributes and degree of textural deterioration. Moreover, the T-Ch treatment was found to be more effective than the T-SA treatment in these aspects. Consequently, the application of composite coatings can effectively delay the decline in quality of refrigerated fish fillets and enhance their preservation efficacy.