The influence of pH on auto-oxidative browning of flavan-3-ols and gallic acid as a promising browning inhibitor

Junfeng Tan; Jean Paul Vincken; Mark G. Sanders; Zhi Lin; Wouter J.C. de Bruijn

doi:10.1016/j.foodchem.2025.143066

The influence of pH on auto-oxidative browning of flavan-3-ols and gallic acid as a promising browning inhibitor

Junfeng Tan, Jean Paul Vincken, Mark G. Sanders, Zhi Lin^*, Wouter J.C. de Bruijn

^*Corresponding author for this work

Research output: Contribution to journal › Article › Academic › peer-review

Abstract

The effect of pH and of flavan-3-ols' structural features on undesired auto-oxidative browning of ready-to-drink green tea is still largely unknown. Thus, we investigated auto-oxidative browning of epicatechin (EC), epicatechin gallate (ECg), epigallocatechin (EGC), epigallocatechin gallate (EGCg) in pH-regulated aqueous model systems. In the typical pH range of green tea infusions (pH 5–7), the brown color intensity of flavan-3-ols after auto-oxidation was found to be EC > ECg > EGCg > EGC. Characterization of brown auto-oxidation products by RP-UHPLC-ESI-HRMSⁿ revealed that most of these can only be formed through multi-step reactions. Therefore, oxidation potentials of the starting flavan-3-ols are unsuitable for predicting browning. Browning inhibition in real green tea can be achieved by maintaining a pH below 4 with either conventional additives (i.e. ascorbic or citric acid) or with gallic acid, a compound naturally abundant in tea. In conclusion, gallic acid is a promising candidate for clean-label auto-oxidative browning inhibition.

Original language	English
Article number	143066
Number of pages	11
Journal	Food Chemistry
Volume	473
DOIs	https://doi.org/10.1016/j.foodchem.2025.143066
Publication status	Published - 1 May 2025

Keywords

Brown
Catechins
Color
Discoloration
oxidation
Tea
Yellow

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https://edepot.wur.nl/687519Licence: CC BY

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title = "The influence of pH on auto-oxidative browning of flavan-3-ols and gallic acid as a promising browning inhibitor",

abstract = "The effect of pH and of flavan-3-ols' structural features on undesired auto-oxidative browning of ready-to-drink green tea is still largely unknown. Thus, we investigated auto-oxidative browning of epicatechin (EC), epicatechin gallate (ECg), epigallocatechin (EGC), epigallocatechin gallate (EGCg) in pH-regulated aqueous model systems. In the typical pH range of green tea infusions (pH 5–7), the brown color intensity of flavan-3-ols after auto-oxidation was found to be EC > ECg > EGCg > EGC. Characterization of brown auto-oxidation products by RP-UHPLC-ESI-HRMSn revealed that most of these can only be formed through multi-step reactions. Therefore, oxidation potentials of the starting flavan-3-ols are unsuitable for predicting browning. Browning inhibition in real green tea can be achieved by maintaining a pH below 4 with either conventional additives (i.e. ascorbic or citric acid) or with gallic acid, a compound naturally abundant in tea. In conclusion, gallic acid is a promising candidate for clean-label auto-oxidative browning inhibition.",

keywords = "Brown, Catechins, Color, Discoloration, oxidation, Tea, Yellow",

author = "Junfeng Tan and Vincken, {Jean Paul} and Sanders, {Mark G.} and Zhi Lin and {de Bruijn}, {Wouter J.C.}",

year = "2025",

month = may,

day = "1",

doi = "10.1016/j.foodchem.2025.143066",

language = "English",

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T1 - The influence of pH on auto-oxidative browning of flavan-3-ols and gallic acid as a promising browning inhibitor

AU - Tan, Junfeng

AU - Vincken, Jean Paul

AU - Sanders, Mark G.

AU - Lin, Zhi

AU - de Bruijn, Wouter J.C.

PY - 2025/5/1

Y1 - 2025/5/1

N2 - The effect of pH and of flavan-3-ols' structural features on undesired auto-oxidative browning of ready-to-drink green tea is still largely unknown. Thus, we investigated auto-oxidative browning of epicatechin (EC), epicatechin gallate (ECg), epigallocatechin (EGC), epigallocatechin gallate (EGCg) in pH-regulated aqueous model systems. In the typical pH range of green tea infusions (pH 5–7), the brown color intensity of flavan-3-ols after auto-oxidation was found to be EC > ECg > EGCg > EGC. Characterization of brown auto-oxidation products by RP-UHPLC-ESI-HRMSn revealed that most of these can only be formed through multi-step reactions. Therefore, oxidation potentials of the starting flavan-3-ols are unsuitable for predicting browning. Browning inhibition in real green tea can be achieved by maintaining a pH below 4 with either conventional additives (i.e. ascorbic or citric acid) or with gallic acid, a compound naturally abundant in tea. In conclusion, gallic acid is a promising candidate for clean-label auto-oxidative browning inhibition.

AB - The effect of pH and of flavan-3-ols' structural features on undesired auto-oxidative browning of ready-to-drink green tea is still largely unknown. Thus, we investigated auto-oxidative browning of epicatechin (EC), epicatechin gallate (ECg), epigallocatechin (EGC), epigallocatechin gallate (EGCg) in pH-regulated aqueous model systems. In the typical pH range of green tea infusions (pH 5–7), the brown color intensity of flavan-3-ols after auto-oxidation was found to be EC > ECg > EGCg > EGC. Characterization of brown auto-oxidation products by RP-UHPLC-ESI-HRMSn revealed that most of these can only be formed through multi-step reactions. Therefore, oxidation potentials of the starting flavan-3-ols are unsuitable for predicting browning. Browning inhibition in real green tea can be achieved by maintaining a pH below 4 with either conventional additives (i.e. ascorbic or citric acid) or with gallic acid, a compound naturally abundant in tea. In conclusion, gallic acid is a promising candidate for clean-label auto-oxidative browning inhibition.

KW - Brown

KW - Catechins

KW - Color

KW - Discoloration

KW - oxidation

KW - Tea

KW - Yellow

U2 - 10.1016/j.foodchem.2025.143066

DO - 10.1016/j.foodchem.2025.143066

M3 - Article

AN - SCOPUS:85216444255

SN - 0308-8146

VL - 473

JO - Food Chemistry

JF - Food Chemistry

M1 - 143066

ER -

The influence of pH on auto-oxidative browning of flavan-3-ols and gallic acid as a promising browning inhibitor

Abstract

Keywords

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