Effect of Pile-Fermentation on the Taste Quality of Dark Tea from a Single Large-Leaf Tea Variety by Uhplc-Ms/Ms and Electronic Tongue

The taste quality of dark tea (DT) is significantly influenced by pile-fermentation. However, no studies have analyzed the formation of taste quality in DT from a single large-leaf tea variety. This study aimed to assess the effect of pile-fermentation on the taste quality of large-leaf DT. Taste evaluation revealed that pile-fermentation reduced astringency and umami while enhancing bitterness. Untargeted metabolomics analysis discovered 14 differential metabolites (catechins, flavonoids, phenolic acids, and organic acids) and L-theanine were associated with the decrease of astringency and umami, respectively, while caffeine (CAFF) was linked to the increase in bitterness. Targeted detection of catechins and purine alkaloids revealed that epigallocatechin gallate, epicatechin gallate, epigallocatechin, and DL-catechin were key compounds in reducing astringency. Meanwhile, CAFF was the primary compound increasing bitterness. These findings can provide a theoretical basis for deep understanding of the impact of pile-fermentation on the taste quality of large-leaf DT.