Impact of Various Microbial-Fermented Methods on the Chemical Profile of Dark Tea Using a Single Raw Tea Material

In
the present study, we produced Pu-erh, Liubao, Qingzhuan, and
Fuzhuan teas using a single raw tea material and applied widely targeted
metabolomics to study the impact of various microbial-fermented methods
on the chemical profile of dark tea. The contents of catechins and
free amino acids decreased drastically, whereas the contents of gallic
acid and theabrownins increased significantly during microbial fermentation.
Pu-erh tea had the highest content of theabrownins (11.82 ± 0.49%).
Moreover, MS-based metabolomics analysis revealed that the different
types of dark teas were significantly different from their raw material.
A total of 85 differential metabolites were screened among 569 metabolites
identified referring to self-compiled database. Glycosylated, hydroxylated,
methylated, and condensed and oxidated products originating from microbial
bioconversion of their corresponding primitive forms were significantly
increased in dark teas. These results suggest that various microbial-fermented
methods greatly affect the metabolic profile of dark tea, which can
provide useful information for dark tea biochemistry research.