The metabolic mechanism of flavonoid glycosides and their contribution to the flavor evolution of white tea during prolonged withering

Abstract

This study was the first to comprehensively investigate the metabolic mechanism of flavonoid glycosides (FGs) and their contribution to flavor evolution during white tea processing using quantitative descriptive analysis, metabolomics, dose-over-threshold factors and pseudo-first-order kinetics. A total of 223 flavonoids were identified. Total FGs decreased from 7.02 mg/g to 4.35 mg/g during processing, compared to fresh leaves. A total of 86 FGs had a significant impact on the flavor evolution and 9 key flavor FGs were identified. The FG biosynthesis pathway was inhibited during withering, while the degradation pathway was enhanced. This promoted the degradation of 9 key flavor FGs following pseudo-first-order kinetics during withering. The degradation of the FGs contributed to increase the taste acceptance of white tea from −4.18 to 1.32. These results demonstrated that water loss stress during withering induces the degradation of key flavor FGs, contributing to the formation of the unique flavor of white tea.