Differences in the quality of black tea (Camellia sinensis var. Yinghong No. 9) in different seasons and the underlying factors

•The taste quality of spring black tea exceeds that of summer black tea.•Glutamic acid and aspartic acid contents differ between spring and summer teas.•Color- and taste-contributing compounds are significantly correlated.•Chromaticity values may reflect the quality of Yinghong No. 9 black tea. Spring green tea is usually considered to be better than summer green tea. Whether this phenomenon applies to black tea is unknown. Black tea produced using Camellia sinensis var. Yinghong No. 9 leaves is popular in South China and analyzed in the study. The taste and color quality of the infusion was higher for spring tea than for summer tea. Compared with summer tea, the main catechin contents were lower in spring tea, whereas caffeine and total amino acid contents were higher, especially glutamic acid, which may be responsible for the differences between teas. Moreover, spring tea had a higher theabrownin content and a lower L* value. The compounds contributing to the infusion taste and color were correlated with the chromaticity value (i.e., useful indicator of black tea quality). This study revealed the seasonal differences in Yinghong No. 9 black tea quality and the key underlying factors.