Taste characteristic and lipase inhibition activity of Sichuan dark tea

Abstract

　The objective of this study was to characterize Sichuan dark tea in terms of its taste characteristics, inhibitory effect on lipid-digesting enzymes, and active components. An analysis of the microbial community structure of Sichuan dark tea on the basis of amplicon sequences revealed the presence of various microorganisms, including Alicyclobacillus, Bacillus, Clostridium, and Weizmannia species. A total of eight taste characteristics were evaluated using a taste sensor system. Compared with green tea, post-fermented tea had lower values for astringency, aftertaste from astringency, umami, richness, and saltiness. Compared with Japanese post-fermented tea, Chinese post-fermented tea had higher values for bitterness, astringency, and umami. The evaluation of lipase activity inhibition (i.e., index of lipid-digesting enzyme inhibition) indicated that the hot water extract of Sichuan dark tea inhibited lipase activity at a lower concentration than that of Pu-erh tea, similar to the Awa Bancha and green tea hot water extracts. The Sichuan dark tea extract was fractionated, after which individual fractions were examined regarding their inhibitory effect on lipase activity. Notably, lipase activity was most significantly inhibited by the theaflavin fraction, followed by the water layer. Furthermore, the theaflavin fraction was subdivided by silica gel column chromatography using acetone/hexane. Among the resulting subfractions, the 50% and 100% hexane layer strongly inhibited lipase activity. Sichuan dark tea, which is relatively non-astringent and full-bodied, inhibited lipid-digesting enzyme activities, suggesting that it contains multiple active components.