Analysis of β-lactoglobulin–epigallocatechin gallate interactions: the antioxidant capacity and effects of polyphenols under different heating conditions in polyphenolic–protein interactions

Abstract

(pH 6.8, 298 K). Circular dichroism (CD) results showed that heat treatment did not result in greatly affected changes in the β-Lg secondary structure induced by β-Lg-EGCG interactions. MALDI-TOF/TOF-MS analysis showed that β-Lg-EGCG covalent conjugates initially formed after heat was applied at 60 °C, and their proportions increased under heat treatment ranging from 85 to 121 °C. The amino group of a lysine residue was further confirmed as the covalent binding site of EGCG to β-Lg. The β-Lg-EGCG interaction showed little effect on the antioxidant capacity (ABTS and ferric reducing antioxidant power (FRAP) values) of EGCG after heat treatment at 25-60 °C, but did induce an obvious reduction at temperatures above 85 °C. This study will provide the foundation for the use of EGCG in processing dairy products (such as milk tea beverages) with desirable nutrition and physiological functions.