Survival-enhancement potential of tea polyphenol-chitosan composites for Pacific oysters (Crassostrea gigas) during anhydrous low-temperature preservation and its multiple mechanisms.

Abstract

A sustainable and efficient method to enhance the survival of Pacific oyster (Crassostrea gigas) during anhydrous transport is needed to provide a theoretical basis for their high-quality and long-distance circulation. Therefore, this study aimed to develop a tea polyphenol-chitosan composite as a green strategy to enhance Pacific oyster (C. gigas) survival during anhydrous low-temperature preservation, and reveals the underlying regulation mechanisms. The results showed that the optimal synergistic formulation (2% chitosan/0.3% tea polyphenol) significantly increased oyster survival to 66.67% compared to 38.89% in controls after 9 days at 4 °C. The obtained composite supported energy balance by maintaining higher glycogen levels at 52.18 mg/g. It also lowered lactate accumulation to 0.083 mmol/gprot and sustained a higher adenylate energy charge of 53.15%. Antioxidant defense was enhanced, as seen in reduced malondialdehyde levels at 44.85 nmol/gprot and decreased reactive oxygen species. Key antioxidant enzyme activities, including SOD, CAT, POD, and GSH-PX, were increased. The tea polyphenol-chitosan composite also showed antimicrobial action by inhibiting microbial growth. The overall survival improvement relies on the synergy between tea polyphenol's antioxidant function, chitosan's film-forming, and antimicrobial properties. This multi-mechanistic approach offers a novel strategy for anhydrous living-preservation of oyster.