Differential binding of gallic acid and epigallocatechin gallate to whey protein affects the interfacial adsorption and gastric digestion of O/W emulsion

Whey protein isolate (WPI) was reacted with 20, 120, and 240 μmol/g gallic acid (GA) or epigallocatechin gallate (EGCG) at 21 °C. Equilibrium dialysis testing indicated a stronger binding capacity of whey proteins with EGCG compared to GA. Both phenolics, especially EGCG, tended to reduce the adsorption of WPI at the oil–water interface and decreased the elasticity modulus (E_d) of the interfacial film. Yet, binding with 20 μmol/g of EGCG and GA (less so) resulted in significantly improved emulsifying activity of WPI, but the emulsion stability was decreased at all phenolic concentrations (except at 240 μmol/g). There was an overall improvement of pepsinolysis of both α-lactalbumin and β-lactoglobulin. In comparison with GA, EGCG yielded more pronounced effects on WPI interfacial adsorption, dilatational rheology, and peptic digestion.