Tea polysaccharide's role in inhibited protein alterations of Hypophthalmichthys molitrix and in-depth molecular interaction mechanism during fluctuated frozen storage

The impact of tea polysaccharides was investigated on the protection of Hypophthalmichthys molitrix myosin during fluctuating frozen storage temperature cycles, addressing a need for safer and more sustainable alternatives to conventional cryoprotectants in the seafood industry . H. molitrix myofibrillar proteins were subjected to treatments with a positive control containing sucrose, sorbitol, and different concentrations of tea polysaccharides (1 and 3%). The study also included control samples. All samples underwent six fluctuating frozen temperature cycles. The control myofibrillar protein samples experienced a substantial decline in protein solubility (51.22–19.56%) and Ca 2+ ATPase (0.354–0.224 mmol/g) activity due to protein unfolding and disruption of intermolecular bonds, as well as an increase in carbonyl content (32.73–54.11 mmol/mg) than other samples. Conversely, 3% of tea polysaccharides effectively prolonged protein stability by establishing strong intermolecular bonds, as evidenced by molecular dynamic simulation. In addition, 3% of tea polysaccharides were also analysed with dense and well-established microstructural properties. In the study, the protective role of galactose in tea polysaccharides is highlighted, which prevents frozen temperature-induced changes by forming strong hydrogen and noncovalent bonds with amino acids. Overall, these findings support the industrial application of tea polysaccharides in enhancing seafood quality during frozen storage. • Tea polysaccharides molecular interaction was explored with fish myosin protein. • Tea polysaccharides showed stronger hydrogen and ionic bonding with protein matrix. • Galactose in tea polysaccharides interacts with several amino acids. • Meanwhile, it inhibited the decline in Ca2+ATPase activity and protein solubility. • Overall, 3% concentration was effective in preserving the H. molitrix quality .