Presence of free gallic acid and gallate moieties reduces auto-oxidative browning of epicatechin (EC) and epicatechin gallate (ECg).

Junfeng Tan, Jean-Paul Vincken, Annemiek van Zadelhoff, Roelant Hilgers, Zhi Lin, Wouter J C de Bruijn

Food chemistry 2023 Nov 01

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Auto-oxidation of flavan-3-ols leads to browning and consequently loss of product quality during storage of ready-to-drink (RTD) green tea. The mechanisms and products of auto-oxidation of galloylated catechins, the major flavan-3-ols in green tea, are still largely unknown. Therefore, we investigated auto-oxidation of epicatechin gallate (ECg) in aqueous model systems. Oxidation products tentatively identified based on MS included δ- or γ-type dehydrodicatechins (DhC2s) as the main contributors to browning. Additionally, various colourless products were detected, including epicatechin (EC) and gallic acid (GA) from degalloylation, ether-linked ε-type DhC2s, and 6 new coupling products of ECg and GA possessing a lactone interflavanic linkage. Supported by density function theory (DFT) calculations, we provide a mechanistic explanation on how presence of gallate moieties (D-ring) and GA affect the reaction pathway. Overall, presence of gallate moieties and GA resulted in a different product profile and less intense auto-oxidative browning of ECg compared to EC. Copyright © 2023 The Author(s). Published by Elsevier Ltd.. All rights reserved.

Citation

Junfeng Tan, Jean-Paul Vincken, Annemiek van Zadelhoff, Roelant Hilgers, Zhi Lin, Wouter J C de Bruijn. Presence of free gallic acid and gallate moieties reduces auto-oxidative browning of epicatechin (EC) and epicatechin gallate (ECg). Food chemistry. 2023 Nov 01;425:136446