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Flavonoids play important roles in tea quality and flavour, but there is still limited information on flavonoid changes in tea leaves during black tea processing. We performed a comprehensive characterization of the dynamic changes of flavonoids during black tea processing by using ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). A total of 203 flavonoids were identified during black tea processing. A significant increase was observed for flavones, flavonols and flavonoid polymers (mainly consisting of theaflavins) in the withering stage, while over 80% of flavonoids decreased in the fermenting stage. In addition, the hydrolysis of flavonoid glycosides mainly occurred in the rolling stage, and the variation of flavonoids was determined by their thermal stability in the drying stage. This study can support development of approaches or strategies to regulate and control composition and content of flavonoids in black tea.
Liu et al. (Fri,) studied this question.