Presence of free gallic acid and gallate moieties reduces auto-oxidative browning of epicatechin (EC) and epicatechin gallate (ECg)
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.
| Main Authors: | , , , , , |
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| Format: | Article/Letter to editor biblioteca |
| Language: | English |
| Subjects: | (-)-Epicatechin (PubChem CID: 72276), (-)-Epicatechin gallate (PubChem CID: 107905), Auto-oxidation, Catechins, Colour, Deesterification, Discolouration, Epimerization, Gallic acid (PubChem CID: 370), O-phenylenediamine (PubChem CID: 7243), Oxidative coupling, Tea, |
| Online Access: | https://research.wur.nl/en/publications/presence-of-free-gallic-acid-and-gallate-moieties-reduces-auto-ox |
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