The effect of different drying temperatures on flavonoid glycosides in white tea: A targeted metabolomics, molecular docking, and simulated reaction study

Abstract

Drying is an important stage used to improve the quality of white tea (WT). However, the effect of the drying temperature on the key taste compounds in WT remains unclear. In this study, targeted metabolomics, molecular docking, and a simulated reaction were used to investigate the transformation mechanism of flavonoid glycosides (FGs) in WT during drying at 60, 80, and 100 °C and its impact on taste. There were 45 differential FGs in WT at three drying temperatures. Compared with the withering samples for 48 h, the total FGs contents at three drying temperatures showed a decreasing trend, with quercetin-3-O-galactoside and kaempferol-3-O-glucoside showing the most degradation. These results were confirmed via a simulated drying reaction of FGs standards. Drying at 80 and 100 °C contributed to the formation of flavonoid-C-glycosides, but only trace amounts of these compounds were observed. In addition, nine key taste FGs were selected using dose-over-threshold values. These FGs regulated the taste of WT, mainly by binding to taste receptors via hydrogen bond, hydrophobic and electrostatic interactions. Finally, the taste acceptability of WT dried at 60 °C was found to be the highest, as this method could properly reduce the contents of FGs, weaken the bitterness and astringency, and retain the sweet and umami taste. This study revealed for the first time the transformation mechanism of sensory-active FGs affected by drying temperature, which provides a novel perspective for the analysis of the formation mechanism of the unique flavor of WT and the optimization of this process.