Chemical profile of a novel ripened Pu-erh tea and its metabolic conversion during pile fermentation

Ripened Pu-erh tea is a unique tea type produced from microbial fermentation. Recently, a novel ripened Pu-erh tea (NPT) produced using a patented pile fermentation method has become increasingly popular due to its improved flavor and enriched bioactive gallic acid (GA). However, the detailed chemical features of NPT and their formation during pile fermentation remain unclear. Herein, untargeted metabolomics revealed enrichment of GA, amino acids, free sugars and reduction in catechins and flavonol glycosides in NPT. Mainly, GA was 1.99 times higher in NPT than traditional Pu-erh tea (p < 0.001). The metabolic changes were tracked during pile fermentation, and possible pathways were mapped. GA enrichment may be produced from enhanced hydrolysis of galloyl catechins and phenolic acid esters. Degradation of flavonol glycosides and formation of other metabolites were observed. This study will advance our understanding of conversions during pile fermentation and provide new insights into directional manufacturing of high-quality ripened tea.