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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. [ABSTRACT FROM AUTHOR]

Withering leads to the formation of high-quality flavor in black tea. This study investigated the effects of natural withering (NW), sun withering (SW), and warm-air withering (WW) on the flavor compounds of withered leaves by using target metabolomic and transcriptomic approaches. The results revealed that 4282, 4770, and 1246 differentially expressed genes (DEGs) were identified in the NW, SW, and WW samples, respectively. The expression of DEGs involved in volatile compound and flavonoid biosynthesis was the highest in the WW sample, which may be the main reason for the significant increase in volatile compound and catechin contents in the WW sample. The withering methods mainly affected the contents of non-proteinaceous amino acids, such as theanine. Withering methods significantly affect the expression levels of DEGs involved in metabolic pathways; this provides a systematic explanation for flavor formation in black tea. • Different withering methods affect the flavor formation of black tea. • The essence of the withering method is the type of stress. • Warm-air withering increased the content of flavor compounds. • Comprehensive explanation of the mechanism of action of withering method of black tea. [ABSTRACT FROM AUTHOR]

Summary: The effects of roasting treatment on sensory quality and related compounds in green tea were investigated. The combined application of roasting temperature and time 100 °C for 90 min, 120 °C for 60 min and 140 °C for 30 min achieved the most satisfying sensory quality. The HPLC analysis showed that the contents of cis‐catechins, bitter and umami amino acids reduced with increase in temperature, while the contents of trans‐catechins and soluble sugar increased with the temperature rise. The content of caffeine and sweet amino acids did not change significantly compared with untreated tea sample. The decrease in cis‐catechins, total polyphenols and bitter amino acids reduced the bitterness and astringency of the green tea, while the increase in total soluble sugars improved the sweetness and mellow taste. The sensory evaluation results showed that the sensory quality of the tea was significantly enhanced through roasting treatment. Roasting treatment significantly improved the sensory quality of green tea. [ABSTRACT FROM AUTHOR]