In Vitro Digestion Properties of Tea Polyphenol Fish Sausage and Its Immunomodulatory Effect in Mice

In order to investigate the in vitro digestive properties of tea polyphenol fish sausage, protein digestibility, particle size, free amino acid content, thiobarbituric acid value and DPPH radical scavenging rate of surimi with different digestion time were studied, and a model was set up with grouping of mice for immunomodulation experiments. The results showed that the addition of 0.2% of tea polyphenols decreased the digestibility of tea polyphenol fish sausage proteins. When the digestion time was 120 min, the maximum in vitro digestibility of proteins of the control group and tea polyphenol group were 54% and 48%, respectively. The free amino acid content and thiobarbituric acid value of the tea polyphenol group were lower than control group, where the particle size and DPPH radical scavenging rate were significantly higher (P<0.05) than control group. Spleen index, serum immunoglobulin IgA and IgG concentrations, serum inflammatory cytokine IL-1β, IL-6, and TNF-α concentrations, and renal CAT, T-AOC, GSH-Px, and SOD activities were significantly higher (P<0.05) and MDA content was extremely significant lower (P<0.01) in mice fed tea polyphenol fish sausage as compared to the model group. Proteins in fish sausage and tea polyphenols affect protein digestion through interaction, while tea polyphenol fish sausage promotes immunomodulation in immunosuppressed mice. The study provides a better understanding of the effects of polyphenols on protein-based foods and provides a theoretical basis for the development of novel functional surimi products.