茶叶烘焙过程中儿茶素的寡聚化机制。

Oligomerization mechanism of tea catechins during tea roasting.

机构信息

Department of Natural Product Chemistry, Graduate School of Biomedical Sciences, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan.

Department of Natural Product Chemistry, School of Pharmaceutical Sciences, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan.

出版信息

Food Chem. 2019 Jul 1;285:252-259. doi: 10.1016/j.foodchem.2019.01.163. Epub 2019 Jan 31.

DOI:10.1016/j.foodchem.2019.01.163

PMID:30797342

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 C NMR spectrum of the oligomer fraction showed signals arising from catechin and sugar residues. Heating of epigallocatechin-3-O-gallate with C-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.

摘要

绿茶的炒制会导致儿茶素的低聚化，从而降低涩味。本研究旨在阐明低聚化机制。低聚物部分的 C NMR 谱显示出源于儿茶素和糖残基的信号。用 C 标记的葡萄糖加热表没食子儿茶素-3-O-没食子酸酯（150°C 加热 2 小时）表明，糖与儿茶素 A 环的缩合导致了低聚化。通过较短时间（30 分钟）加热获得的二聚产物表明，糖和儿茶素 A 环之间发生了交联。此外，用儿茶素 A 环类似物根皮苷与葡萄糖、甲基乙二醛和二羟丙酮加热，证实了基本机制包括儿茶素 A 环亚甲基碳原子与葡萄糖及其热解产物的羰基碳原子的反应。