The contents of extractable components and taste characteristics of Pu-erh raw tea infusions obtained at different brewing times were analyzed by employing ultra performance liquid chromatography-high resolution mass spectrometry (UPLC-HRMS) combined with sensory evaluatio in this study. The results showed that a total of 138 extractable components were identified, the predominant ones being amino acids, catechins and their derivatives, phenolic acids and their derivatives, flavonoids and alkaloids. These substances made a significant contribution to the umami, bitterness and astringency of tea influsions. The sensory score for taste of Pu-erh raw tea infusion was positively correlated with the degree of bitterness, astringency and thickness; there was also a positive correlation between the total amount of extractable components and the sensory score for taste for tea infusion obtained at each brewing cycle. The total amount of extractable components and the taste score reached their maximum values at the second brewing cycle, and then the total amount of extractable components decreased and the taste became increasingly plainer and thinner with increasing number of brewing cycles. These findings help to reveal the durability of Yunnan Pu-erh raw tea and the taste change of tea infusion during the brewing process.

The dominant fungi in Fuzhuan tea produced in Hunan were isolated and identified by morphological analysis and comparative analysis of internal transcribed spacer (ITS) sequences. Then, single-strain fermentation of low-grade Yunnan large-leafed green tea was carried out using the isolated fungi, and changes in the contents of the main components of green tea were analyzed before and after fermentation. The results showed that four dominant strains named as J1-J4 were isolated from Fuzhuan tea. J1 was identified as Aspergillus chevalieri, and J2, J3 and J4 as Aspergillus cristatus. The contents of tea polyphenols and total flavonoids in green tea significantly fell after fermentation, whereas the content of theabrownin increased significantly. The total alkaloid content significantly increased after fermentation with A. chevalieri, but significantly decreased after fermentation with A. cristatus. The contents of catechin components varied significantly after fermentation; ester catechin content decreased significantly, while the contents of three non-ester catechins (epicatechin, gallocatechin, and epigallocatechin) increased significantly. Theaflavin content was significantly decreased by strains J1, J2 and J3 but significantly increased by strain J4. The contents of amino acids also changed significantly. The results of this study can provide a theoretical basis for the development of high-value products from low-grade Yunnan large-leafed green tea.