Roasting process shaping the chemical profile of roasted green tea and the association with aroma features

Sensory and chemical characteristics of Tieguanyin oolong tea after roasting

“…The other part substances, decreasing with the roasting time, included flavonol glycosides (except myricetin), flavan-3-ols, amino acids, phenolic acids (except GA, dihydroxybenzoic acid, and hydroxy-benzoic acid), and saccharides. Zhu et al (2021) reported that deep-roasting treatment could decrease the contents of most catechins and flavonol glycosides of green tea. The reduction of catechins and flavonol glycosides could contribute to the attenuation of astringency and bitterness ( Chen, Kuo, Yang, Li, & Tzen, 2013 ).…”

“…Most of these aroma substances belonged to pyrazines, pyrroles, and furans. These substances were produced in the Maillard reaction and caramelization reaction of sugars, amino acids, and pectins during the roasting process ( Ho et al, 2015 , Zhu et al, 2021 ). For example, 2,5-dimethyl-pyrazine was detected in the model thermal reaction of d -glucose and l -theanine ( Guo et al, 2018 ).…”

“…It’s reported that epimerization was an important structural transformation of flavan-3-ols in the roasting process of green tea ( Mizukami, Sawai, & Yamaguchi, 2008 ). Flavonoid profiles could distinguish different roasted green teas ( Zhu et al, 2021 ). Besides, roasting can promote the oxidative decomposition of catechins, aldehydes, alcohols, and other substances ( Zhang, Ho, Zhou, Santos, Armstrong, & Granato, 2019 ).…”

“…On the other hand, roasting can also change the volatile substances directly, thereby affect the aroma of roasted tea. The roasting process can significantly increase the contents of total aldehydes, total ketones, total esters, total furans, total pyrroles, and pyrazines of tea ( Zhu et al, 2021 ). The main characteristic aroma substances induced by roasting include pyrazines, pyrroles, and furans, with pyrazines being one of the major odorants contributing to the aroma of roasted tea ( KAWAKAMI and YAMANISHI, 1999 , Sasaki et al, 2017 ).…”

Effect of Yellowing Duration on the Chemical Profile of Yellow Tea and the Associations with Sensory Traits

“…Gallic acid is an important hydrolysis product of gallated catechins [ 14 ], which was increased with yellowing duration. Catechins, flavones and flavonol glycosides are important contributors to the bitterness and astringency of teas [ 15 ], which were susceptible to high temperature due to degradation, oxidation and hydrolysis reactions [ 1 , 14 , 16 ]. Thus, oxidation/polymerization may also occur in flavonoid compounds in addition to hydrolysis reactions.…”