Abstract: To explore the effect of sun-drying process on the taste quality and non-volatile metabolites of Congou black tea, fresh leaves of two cultivars, ‘Zhongcha 111’ and ‘Fu’an Dabaicha’, were processed into sun-dried black tea and conventional black tea (control). The tea samples were analyzed using sensory evaluation, quantitative chemical analysis, and ultra-high performance liquid chromatography-high-resolution mass spectrometry. The results showed that the sun-drying process had a significant effect on the taste, aroma, and infusion color factors of Congou black tea, the effect being most pronounced on taste scores (differing by 4–5 points) compared with the control. The sun-drying process significantly affected various catechin and amino acid components, but there were differences in the response characteristics among different cultivars. A total of 124 metabolites were identified by ultra-high performance liquid chromatography-Q-Exactive mass spectrometry, including 10 alkaloids, 17 amino acids, 4 aroma glycosides, 2 carbohydrates, 12 dimeric catechins, 7 N-ethyl-2-pyrrolidinone-substituted flavan-3-ols (EPSF), 9 catechins, 33 flavonoid (flavonol) glycosides, 7 lipids, 4 organic acids, 12 phenolic acids, and 7 other compounds. Compared with the control, 60 differential metabolites were found in sun-dried ‘Zhongcha 111’ black tea and 63 in sun-dried ‘Fu’an Dabaicha’ black tea. The contents of flavonoid (flavonol) glycosides, amino acids, and catechins in sun-dried black tea were relatively low, while the content of carbohydrates was relatively high. In summary, the sun-drying process significantly affected the taste quality and non-volatile metabolites of Congou black tea, with different cultivars showing varied responses, providing a theoretical basis for optimizing the sun-drying time of black tea.

Key words: Congou black tea; sun-drying process; sun drying; taste; metabolomics