Cyclic freeze-thaw processing of polyvinyl alcohol/gallic acid grafted chitosan hydrogels: an effective way to delay protein deterioration of refrigerated sea bass (lateolabrax maculatus).

Given the susceptibility of sea bass (Lateolabrax maculatus) to quality deterioration due to protein and lipid oxidation during refrigerated storage, there is a need for advanced preservation methods. Currently, conventional approaches like commercial fresh-keeping pads have limitations in fully arresting these oxidative processes. This study developed a CS-GA/PVA hydrogel based on chitosan-gallic acid (CS-GA) and polyvinyl alcohol (PVA) and applied it as a fresh-keeping pad for sea bass (Lateolabrax maculatus). The hydrogel's effects on the oxidative stability of myofibrillar proteins (MPs) and lipids in refrigerated sea bass were systematically investigated. Samples were randomly divided into four groups, and MPs were extracted every two days to assess their oxidation levels and conformational changes. Compared to the control (CK) and commercial fresh-keeping pad (X) groups, the samples treated with the CS-GA/PVA (PCG) hydrogel significantly reduced oxidative damage and aggregation of MPs. The hydrogel effectively delayed decreases in total sulfhydryl content and Ca-ATPase activity, as well as increases in malondialdehyde (MDA) levels and decreases in protein solubility. The results of structural analysis revealed that PCG hydrogel maintained the secondary and tertiary structures of MPs, minimizing the exposure of hydrophobic residues. Moreover, microstructural observations confirmed that the hydrogel preserved the integrity of MPs, preventing structural collapse during storage. These findings demonstrate the potential of the CS-GA/PVA hydrogel as an effective strategy to mitigate protein oxidation and aggregation in fish products. Therefore, the PCG hydrogel shows promise as a strategy for maintaining the quality of sea bass and achieving a long-term preservation effect.