Characteristic Fluctuations in Glycosidically Bound Volatiles during Tea Processing and Identification of Their Unstable Derivatives

Abstract

A recently developed method enabled us to simultaneously characterize and quantitate glycosidically bound volatiles (GBVs) at picomole levels using liquid chromatography-mass spectrometry (LC-MS). On the basis of the analytical data it is possible to screen tea varieties most suitable for black tea processing, in which higher concentrations of primeverosides accumulate. The primeverosides decreased at the rolling step in black tea processing, whereas the glucopyranosides did not change much. The total contents of GBVs gradually increased at the withering steps and then remarkably increased after the fixing step at 230 °C, during oolong tea processing. The presence of 6'-O-malonyl ester type β-D-glucopyranosides in the tea samples suggested a contribution to the increment in glucopyranosides during oolong tea processing. The method was also used to analyze GBVs and their derivatives to understand their possible role in the metabolic pathway of tea.

Assessment of Variations in Round Green Tea Volatile Metabolites During Manufacturing and Effect of Second-Drying Temperature via Nontargeted Metabolomic Analysis

“…The increase in glycoside-derived volatiles in fixation process may be due to the simultaneous enzymatic hydrolysis and thermochemical degradation of glycosides. This result is consistent with the previous reports that lipids and glycosides undergo drastic changes during fixation ( 11 , 29 , 40 ).…”

Effect of red light on the composition of metabolites in tea leaves during the withering process using untargeted metabolomics

“…Many GBVs in tea have been isolated and identified. They are stored in vacuoles 39 and actively participate in the formation of aromas in black and oolong teas 40,41 . In the present study, decreases in the levels of linalool oxide primeveroside and phenylethyl primeveroside in the middle and late stages of red light withering (see Supporting information, Figs S5 and S6) may be a result of enzymatic hydrolysis by endogenous glycosidases.…”

Methyl Jasmonate-Induced Changes of Flavor Profiles During the Processing of Green, Oolong, and Black Tea

“…However, this is in contrast to our study in which higher relative abundances of these compounds were detected in MeJA-treated samples. One study has posited the hypothesis that these volatile compounds are derived from glycosidically bound precursors or oxidized and esterized intermediates (Cui et al, 2016). Such modification reactions could be triggered by MeJA treatment activating a series of differential expression of genes related to the LOX pathway (e.g., LOX and O-methyltransferase), TPs pathway (e.g., GPP synthase and UDP-glycosyltransferase), and shikimate pathway (e.g., UDP-glycosyltransferase and cytochrome P450s) (Cui et al, 2016; Tamogami et al, 2016; Cna’ani et al, 2017).…”