Umami amino acids inhibit the bitter and astringent taste presentation of catechins, which is essential for the taste regulation of green tea. In this study, the concentration–intensity trends and taste threshold properties of major catechin monomers were investigated using an electronic tongue. The taste and chemical structure interactions between the ester‐type catechins and theanine, glutamic acid (Glu), and aspartic acid (Asp) were further analyzed by in vitro simulation and analysis of their reciprocal chemical structures. The results showed that the bitterness and astringency of the major catechin monomers increased with increasing concentration, and their bitterness thresholds and their electron tongue response values were higher than those of the astringent values, while the bitterness and astringency of the ester‐type catechins were higher than those of the nonester type. The three amino acids inhibited the bitterness intensity of ester catechins (epigallocatechin gallate, epicatechin gallate, and gallocatechin gallate) at different concentrations, and the effects on the astringency intensity of ester catechins were complicated. Ester catechins significantly enhanced the umami intensity of theanine, Glu, and Asp at different concentrations. Their reciprocal chemical structures showed that hydrogen bonding was the main interaction force between the three ester‐type catechins and the umami amino acids, with theanine and Glu interacting more strongly with ester‐type catechins than Asp, and Glu having a lower binding energy to ester‐type catechins, which bonded more easily.

Rich secondary metabolites render black tea its unique flavor and health benefits, making it the most widely consumed tea in the world. Yet, few studies have investigated the differences in secondary metabolites between black-tea varieties and whether secondary metabolites have antidisease activity. Using gas chromatography-tandem mass spectrometry metabolomics and the Traditional Chinese Herbal Medicine Systems Pharmacology Platform database, this study investigated differences in the secondary metabolites of varieties of black tea, including Fuding Dabai (FD), Golden Guanyin (JGY), Golden Peony (JMD), Qianmei 601 (Q601), and Qiancha 1 (Q). Then, the antidisease activity of their secondary metabolites was evaluated. A total of 657 secondary metabolites were identified in the different black-tea varieties. Among them, 183 metabolites had antidisease activity, 113 were key active ingredients in traditional Chinese medicine (TCM), 73.22% had multiple antidisease activities, and all were mainly flavonoids and phenolic acids. The specific differential metabolites of FD vs JGY, FD vs JMD, FD vs Q, and FD vs Q601 and their disease-resistance activities were (67, 17), (24, 5), (26, 6), and (65, 8), respectively. The main enriched metabolic pathways were phenylpropanoid biosynthesis, biosynthesis of secondary metabolites, flavonoid biosynthesis, and metabolic pathways, with four, four, six, and five key metabolites, respectively. Flavonoid and phenolic acid secondary metabolites were more correlated with antidisease activity and key active TCM ingredients. Conclusion: The types of secondary metabolites were consistent among the different black-tea varieties, while the relative contents differed significantly, with greater differences in secondary metabolites between JGY and Q601. Flavonoid and phenolic acid secondary metabolites were the main contributors to the differences in secondary metabolites and the disease-resistance activity of different black-tea varieties, followed by lignans with coumarins, alkaloids, and tannins also contributing to disease-resistance activity. These findings improve our understanding of the secondary metabolites and health benefits of different varieties of black tea.