Effect of the Number of Gallate Groups of Polyphenols on the Structure, Gel Properties, and Biological Activity of Soy Protein Fibrils

Abstract

Amyloid fibril hydrogels prepared via protein acid heating currently exhibit inadequate gel properties and biological activity. These limitations can be addressed by modifying the amyloid fibrils with polyphenols. In this study, two types of polyphenols—tannic acid (TA) and gallic acid (GA)—were selected to prepare hydrogels with soy protein fibrils (SPIFs) at varying proportions to investigate structure, gel properties, and biological activity. TEM results revealed that polyphenols are deposited on the surface of SPIFs by hydrogen bonding and hydrophobic interaction to form hybrid supramolecules. The greater the mass ratio of polyphenols to SPIF, the more pronounced the structural changes. When the mass ratios of TA, GA, and SPIF were 1:20 and 1:2, respectively, the β-sheet content reached the maximum. The gel strength increased by 6 times and 5 times, respectively, with the modulus reaching 334.91 Pa and 317.79 Pa, respectively. The hydrogels exhibited optimal apparent viscosity and structural recovery properties. Bacteriostatic and cytotoxicity tests demonstrated that the hydrogels exhibited excellent antibacterial properties while maintaining safety. In summary, TA demonstrates significant advantages in remodeling SPIF at low concentrations, thereby enhancing the gel characteristics and antibacterial properties of the hydrogel.