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Issue 5, 2020
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Analysis of β-lactoglobulin–epigallocatechin gallate interactions: the antioxidant capacity and effects of polyphenols under different heating conditions in polyphenolic–protein interactions

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Abstract

The interaction and antioxidant capacity between epigallocatechin gallate (EGCG) and β-lactoglobulin (β-Lg) under thermal treatments at 25–121 °C were investigated in this study. Fluorescence spectroscopy analysis showed that EGCG complexed with β-Lg mainly via non-covalent interactions and the binding affinity of EGCG to β-Lg was enhanced with heat treatment. EGCG showed a strong binding affinity to β-Lg after 85 °C heat treatment was applied, with a Ka of 30.69 (±0.87) × 105 M−1 (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.

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

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Article information


Submitted
09 Mar 2020
Accepted
28 Apr 2020
First published
28 Apr 2020

Food Funct., 2020,11, 3867-3878
Article type
Paper

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

X. Qie, Y. Chen, W. Quan, Z. Wang, M. Zeng, F. Qin, J. Chen and Z. He, Food Funct., 2020, 11, 3867
DOI: 10.1039/D0FO00627K

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