Integration of non-targeted metabolomics and E-tongue evaluation reveals the chemical variation and taste characteristics of five typical dark teas

The chemical profile and taste quality of various dark teas vary considerably due to the huge differences in tea cultivar, processing technology, and production region. Herein, we integrated liquid chromatography-mass spectrometry and electronic tongue to reveal variations in chemical profile and taste quality of five typical dark teas, namely Pu-erh tea (PET), Fuzhuan tea (FZT), Qingzhuan tea (QZT), Kangzhuan tea (KZT), and Liubao tea (LBT), and elucidate chemical basis for their taste quality. The chemical phenotypes of dark teas were classified into FZT, PET, and QZT-KZT-LBT, whereas their taste phenotypes were classified into FZT, PET-QZT, and KZT-LBT. Totally, 49 compounds were identified as differential metabolites, with higher contents of catechins and flavonoid glycosides in FZT, and higher contents of catechin derivatives, flavonoids, and alkaloids in PET. PET had the strongest bitterness and aftertaste-bitterness, while FZT showed the strongest astringency, aftertaste-astringency, and saltiness among five typical dark teas. The bitterness and aftertaste-bitterness of dark teas were negatively associated with polyphenols, flavonoids, and polysaccharides, but positively associated with theabrownins; their aftertaste-astringency was positively related to polyphenols and flavonoids, but negatively related to theabrownins. This study will guide dark tea taste quality control and lay a foundation for comparing their health benefits.