Targeted metabolomics revealed key compounds during the pile fermentation process of Liupao tea

The pile fermentation process tea is a key step in the formation of the flavor of Liupao tea. This study analyzed the changes in sensory characteristics, polyphenolic compounds, and purine content of Liupao tea samples under different fermentation times. The research find that during the fermentation process of Liupao tea, the content of polyphenolic compounds significantly decreased, while the alkaloids showed an increasing trend. Based on the changes in compound and sensory evaluation, the optimal pile fermentation time for Liupao tea was 45 day. Through multivariate statistical analysis, GA, EC, EGC, EGCG, ECG, and C (VIP ≥ 1) were identified as key compounds that change significantly during the pile fermentation process. By establishing a linear regression analysis model (PLS) between compound content and fermentation time, it was found that EGC, C, EC, EGCG and ECG had a good linear relationship with pile fermentation time (r<-0.7), which can serve as key compounds for determining the pile fermentation time of Liupao tea.