The Impact of Gallic Acid Binding on the Foam and Interfacial Properties of Whey Protein Isolate Under Weak Acidic Conditions

The interfacial and foam properties of proteins can be enhanced by altering the interactions between polyphenols and proteins. The aim of this study was to determine the influence of gallic acid (GA) on the structural properties of whey protein isolate (WPI), specifically focusing on particle size, potential, and surface hydrophobicity, as well as the subsequent alterations in its interfacial and foam properties when utilized as a foaming agent. An increase in turbidity and a decrease in particle size suggested the formation of a soluble complex between GA and WPI at a pH of 6. The results from fluorescence spectroscopy and surface hydrophobicity analyses indicated that the primary interactions between GA and WPI are characterized by hydrogen bonding and hydrophobic interactions. The reduction in particle size enhances the capacity of WPI/GA complexes to lower the surface pressure, thereby demonstrating significant efficacy at the macroscopic scale. Furthermore, the structural connectivity of GA facilitates the formation of a stable interfacial film at the air–water interface by WPI/GA, resulting in high foam stability at a macroscopic level. This research contributes to a deeper understanding of the application of protein–polyphenol complexes as surfactants and provides theoretical support for their use in food applications.