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Oligomerization mechanism of tea catechins during tea roasting


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Title: Oligomerization mechanism of tea catechins during tea roasting
Authors: Morikawa, Hitomi / Okuda, Keita / Kunihira, Yuji / Inada, Aoi / Miyagi, Chika / Matsuo, Yosuke / Saito, Yoshinori / Tanaka, Takashi
Issue Date: 1-Jul-2019
Publisher: Elsevier Ltd.
Citation: Food Chemistry, 285, pp.252-259; 2019
Abstract: Roasting of green tea causes oligomerization of tea catechins, which decreases the astringency. The aim of this study was to elucidate the oligomerization mechanism. The 13C NMR spectrum of the oligomer fraction showed signals arising from catechin and sugar residues. Heating of epigallocatechin-3-O-gallate with 13C-labeled glucose (150 °C for 2 h) suggested that condensation of sugars with catechin A-rings caused the oligomerization. The dimeric product obtained by heating for a shorter period (30 min)suggested cross-linking occurred between sugars and catechin A-rings. Furthermore, heating of phloroglucinol, a catechin A-ring mimic, with glucose, methylglyoxal, and dihydroxyacetone, confirmed that the basic mechanism included reaction of the catechin A-ring methine carbons with carbonyl carbons of glucose and their pyrolysis products.
Keywords: roasted tea / catechin / sugar / methylglyoxal / dihydroxyacetone / phloroglucinol / polyphenol
URI: http://hdl.handle.net/10069/38867
ISSN: 03088146
DOI: 10.1016/j.foodchem.2019.01.163
Rights: ©2019, Elsevier. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
Type: Journal Article
Text Version: author
Appears in Collections:Articles in academic journal

Citable URI : http://hdl.handle.net/10069/38867

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