Gallic Acid Improves the Emulsion Capacity of Pectin–Whey Protein Nanofiber Complexes by Altering the Mode of Fiber Entanglement

Protein–polysaccharide–polyphenol ternary complexes could be used to prepare a food-grade Pickering emulsion. However, the mechanism by which polyphenols improve the emulsifying ability of fibrous proteins and polysaccharide complexes is still unclear. In this study, we prepared a complex of gallic acid (GA)-grafted pectin (pectin-GA) and whey protein nanofibers (WPF) to explore the mechanism of GA that improves the emulsification properties of the complex. The results indicate that GA hinders the orderly arrangement of pectin chains and exposes more hydrophobic groups of WPF in the complex. Under the action of GA groups, pectin and WPF transformed from a bundle-like fiber aggregation network to a disordered, intertwined network. These changes enhanced the interfacial wettability of the complex, forming a tighter continuous network around the oil droplets, thereby improving the stability of the emulsion. The findings provide new perspectives on the mechanism by which polyphenols regulate the emulsifying capacity of polysaccharide–protein complexes.