This project aimed to evaluate the effects of gallic acid (GA) and protocatechuic acid (PA) grafted onto chitosan (CS) on the improved quality of sea bass (Lateolabrax japonicus) during refrigerated storage. The incorporation of GA and PA onto CS (CS-g-GA and CS-g-PA) were achieved by the carbodiimide-mediated grafting procedure. Samples were treated with different solutions (deionized water [CK], 1% CS [m/v], 1% CS-g-GA [m/v], and 1% CS-g-PA [m/v]) for 10 min, which were then stored at 4 °C. Microbiological quality, including total viable counts (TVC), psychrophilic bacterial counts (PBC), Pseudomonas bacterial counts, and H2 S-producing bacterial counts were measured. Physicochemical parameters, including pH, total volatile basic nitrogen (TVB-N), thiobarbituric acid (TBA) value, water holding capacity (WHC), and K value, were measured. The changes in protein characteristics, including sulfhydryl groups (SH), Ca2+ -ATPase activity, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and tertiary structure of protein were analyzed periodically, along with texture profile analysis (TPA). The results demonstrated that the CS copolymers treatment exhibited better preservation effects. The CS-g-GA and CS-g-PA treatments could significantly inhibit the growth of microorganisms and retard the increase of pH, TVB-N, TBA, WHC, and K-value during refrigerated storage compared with the CK and CS groups. Additionally, the CS-g-GA and CS-g-PA treatments could delay the protein oxidation by keeping a higher SH level and Ca2+ -ATPase activity. The CS copolymers treatment could also extend the shelf life for another 6 days compared with that of CK. As a result, CS copolymers can be employed in a promising method for the preservation of sea bass. PRACTICAL APPLICATION: The incorporation of gallic acid and protocatechuic acid onto chitosan (CS-g-GA and CS-g-PA) showed superior antioxidant and antimicrobial activities when applied on sea bass. The CS-g-GA and CS-g-PA coatings could maintain the quality and freshness of refrigerated sea bass. Additionally, this research could provide a theoretical basis for the application of graft copolymers on the preservation of aquatic products.

中文翻译：

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壳聚糖接枝酚酸涂层对海鲈（Lateolabrax japonicus）冷藏期间微生物、理化和蛋白质变化的影响

该项目旨在评估嫁接在壳聚糖 (CS) 上的没食子酸 (GA) 和原儿茶酸 (PA) 对冷藏储存期间鲈鱼 (Lateolabrax japonicus) 品质改善的影响。GA 和 PA 结合到 CS（CS-g-GA 和 CS-g-PA）上是通过碳二亚胺介导的接枝程序实现的。样品用不同的溶液（去离子水 [CK]、1% CS [m/v]、1% CS-g-GA [m/v] 和 1% CS-g-PA [m/v]）处理10 分钟，然后在 4 °C 下储存。测量微生物质量，包括总活菌数 (TVC)、嗜冷菌数 (PBC)、假单胞菌菌数和产 H2 S 菌数。测量理化参数，包括 pH、总挥发性碱性氮 (TVB-N)、硫代巴比妥酸 (TBA) 值、持水能力 (WHC) 和 K 值。定期分析蛋白质特征的变化，包括巯基 (SH)、Ca2+ -ATPase 活性、十二烷基硫酸钠-聚丙烯酰胺凝胶电泳 (SDS-PAGE) 和蛋白质的三级结构，以及质地剖面分析 (TPA)。结果表明，CS共聚物处理表现出更好的保鲜效果。与CK和CS组相比，CS-g-GA和CS-g-PA处理可以显着抑制微生物的生长，延缓冷藏过程中pH、TVB-N、TBA、WHC和K值的升高。此外，CS-g-GA 和 CS-g-PA 处理可以通过保持较高的 SH 水平和 Ca2+ -ATPase 活性来延迟蛋白质氧化。与 CK 相比，CS 共聚物处理还可以将保质期再延长 6 天。因此，CS共聚物可用于保存鲈鱼的有前途的方法。实际应用：将没食子酸和原儿茶酸结合到壳聚糖（CS-g-GA 和 CS-g-PA）上时，在鲈鱼上使用时表现出优异的抗氧化和抗菌活性。CS-g-GA 和 CS-g-PA 涂层可以保持冷藏鲈鱼的质量和新鲜度。此外，该研究可为接枝共聚物在水产品保鲜中的应用提供理论依据。CS-g-GA 和 CS-g-PA 涂层可以保持冷藏鲈鱼的质量和新鲜度。此外，该研究可为接枝共聚物在水产品保鲜中的应用提供理论依据。CS-g-GA 和 CS-g-PA 涂层可以保持冷藏鲈鱼的质量和新鲜度。此外，该研究可为接枝共聚物在水产品保鲜中的应用提供理论依据。