Effects of post-harvest processing and 10-year natural aging on quality-related metabolites and taste quality of white peony tea

The unique taste qualities of white peony tea (WPT) are controlled by post-harvest processing and aging processes, but it is not yet clear which process is the most critical and which phytochemical components make the key contributions. In this study, metabolite absolute quantification, chemometrics, dose-over-threshold, and transcriptomics were used to analyze the molecular mechanisms of quality-related metabolites and taste changes of WPT samples during post-harvest processing and 10-year natural aging processes. The results show that WPT metabolites changed more during processing (with a coefficient of variation of 23.3%) than during 10 years of natural aging (18.4%), in which the withering process was the most critical. Twenty-three compounds made key contributions to changes in WPT taste, with the degradation of flavonol glycosides and catechins playing a dominant role. Seven transcription factors and nine target genes were the key regulatory genes for the degradation of flavonoid glycosides and catechins during withering enzymatic reactions. This study clarifies the notion that the changes in metabolite content induced by enzymatic reaction during withering play a key role in the formation of the unique taste quality of WPT, and it provides a basis for the quality improvement and targeted regulation of WPT.