Model Studies on the Reaction Products Formed at Roasting Temperatures from either Catechin or Tea Powder in the Presence of Glucose

Abstract

During tea processing, roasting significantly affects the transformation pathway of catechins. When (−)-epigallocatechin gallate (EGCG) and glucose were roasted at different pH values, the degree of degradation and isomerization of EGCG was the lowest at pH 7 and the highest at pH 8. Thirty-five products were found in the model reaction of EGCG and glucose under high temperatures, of which four EGCG−glucose adducts were identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and nuclear magnetic resonance (NMR). In addition, catechins, gallic acid, and theanine in tea with added glucose were significantly reduced during roasting. The contents of four EGCG−glucose adducts were increased significantly at 150 °C after 30 min and dropped gradually after 60 min. Therefore, based on the present study, EGCG could form crosslinks with glucose under high temperatures in a short time, which provides insight for tea processing and synthesis of catechin−sugar adducts.

Effect of the C-Ring Structure of Flavonoids on the Yield of Adducts Formed by the Linkage of the Active Site at the A-Ring and Amadori Rearrangement Products during the Maillard Intermediate Preparation

“…As shown in Figure S7, [M Flavonoid+ d ‑xylose–H 2 O – H] − parent ions formed, and this phenomenon showed that DM, DQ, EC, EGC, and PG could react with d -xylose to form adducts. The results were in line with the findings by Jiang et al While the di-MGO adduct of MGO with EGCG at the C-6 or C-8 position was discovered at a slightly alkaline pH, no di-ARP adduct of the ARP with the flavonoids was detected in this study.…”

Decoding the Specific Roasty Aroma Wuyi Rock Tea (Camellia sinensis: Dahongpao) by the Sensomics Approach

“…Theanine, a free amino acid only abundant in C. sinensis, is an odorless precursor participated in the formation of pyrazines during tea processing. , A variety of parameters including time, pH, temperature, water, and enzymes play key roles in the formation of pyrazines. , Trimethylpyrazine can be generated by heating glycine-sucrose and L -ascorbic acid-glycine model systems, or L -serine and -threonine alone, and it was the main product of the above Maillard reactions. 2-Ethyl-3,5-dimethylpyrazine can be generated via thermal treatment in the d -glucose and alanine model system, , or L -threonine .…”

Two new catechins from Zijuan green tea enhance the fitness and lifespan of Caenorhabditis elegans via insulin-like signaling pathways

“…1). Although EGCG 8-C-glucose is easily formed during the roasting of green tea, 43,47 ECG 8-C-glucose has not been reported before, let alone an additional ( E )- p -coumaroyl group sitting at the glucose moiety in the structure of zijuanin E. Zijuanin F is special in the phenylpropanoid group substituted at C-6 of the A ring.…”