Based on Multi-Spectral Technology, the Interaction Mechanism of Xylitol, Stearic Acid and Gelatin Was Explored

To optimize the properties of gelatin-based films and expand their applications in the food industry, this study systematically investigated the interaction mechanisms between xylitol (Xyl), stearic acid (Ste), and gelatin (GA) using multispectral technology combined with thermodynamic analysis and molecular docking simulations. The results demonstrated that both Xyl and Ste formed stable non-covalent complexes with GA through static quenching, and the binding processes are spontaneous. The Xyl-GA complex acts on the amino acid residues of glycine GLY21, alanine ALA20, glutamine GLN19 and arginine ARG17, with a binding constant of 1.35 L/mol and a binding site number of 0.17, and elevated temperature can effectively promote its binding reaction. In contrast, stearic acid–gelatin forms stable complexes with alanine ALA20, valine VAL22, methionine MET23, phenylalanine PHE25 and arginine ARG17 through hydrogen bonds and van der Waals forces. The increase in temperature will weaken the binding force between Ste and GA. Synchronous fluorescence spectroscopy verified that the binding sites of xylitol and stearic acid were adjacent to the tryptophan residues of gelatin. Three-dimensional fluorescence spectroscopy further confirmed that the combination of the two additives can induce conformational changes in the gelatin polypeptide chain. This study characterized the binding sites, characteristic parameters and interaction rules of xylitol/stearic acid and gelatin, and the results may provide partial theoretical guidance for targeted modification of high-performance gelatin-based food packaging materials.