Characterization of OSA-starch/tea polyphenol complexes with enhanced oil-water interfacial properties by molecular dynamics simulation and isothermal titration calorimetry.

Modifying the structure of natural emulsifiers can significantly alter their bulk properties and interfacial behavior. In this study, the binding mechanisms and interfacial adsorption of octenyl succinic anhydride starch (OSA-starch)/ epigallocatechin-3-gallate (EGCG) complexes were investigated for developing functional emulsifiers. Molecular dynamics simulations and isothermal titration calorimetry demonstrated that OSA-starch and EGCG interacted via van der Waals forces, electrostatic interactions, and hydrogen bonding. With EGCG concentrations increased from 0.05 % to 0.20 %, the number of hydrogen bonds between OSA-starch and EGCG changed from 8 to 26. The improved oil-water interfacial properties were evidenced by contact angle measurements and dynamic interfacial tension analysis. Specifically, when EGCG concentration was 0.05 %, the contact angle of the OSA-starch/EGCG complexes was increased to 71.29°, while the interfacial diffusion rate was rose to 0.0252 mN m s. The structural features and interfacial behaviors of OSA-starch/EGCG complexes were closely interconnected, offering significant insights into the regulation of interfaces.