Abstract: In this current work, the interaction and assemble behavior between polyphenols with different structures and fish skin gelatin (GLA) were evaluated, which is expected to provide a scientific basis for the processing of aquatic products, the utilization of by-products and the exploration of novel food ingredients, and to provide a theoretical guidance for the application of polyphenol-protein complexes in food fields. Three kinds of polyphenols with different numbers of pyrogallol groups including tannic acid (TA), epigallocatechin gallate (EGCG) and gallic acid (GA) were selected for this study. The impact of polyphenol concentration and pH on the assembly behavior of GLA-polyphenol systems was evaluated based on turbidity and particle size. Fluorescence spectroscopy and isothermal titration calorimetry (ITC) were used to explore the interaction mechanism between polyphenols and GLA. The results showed that TA and EGCG could be assembled with GLA at a certain concentration to form polyphenol-GLA nanocomposites, whose transmittance could be reversibly tuned by changing the pH. Fluorescence spectroscopic analysis revealed that the formation of GLA-polyphenol complexes could statically quench the endogenous fluorescence of GLA. Isothermal titration calorimetry showed that the main forces of the interaction between TA and GLA were hydrogen bonds and van der Waals forces, while the interaction between EGCG and GLA was mainly driven by electrostatic interaction.

Key words: fish skin gelatin; polyphenol; interaction; fluorescence spectrum; isothermal titration calorimetry