Effects of different withering methods on the taste of Keemun black tea

In this study, quantitative taste evaluation based on sense and electronic tongue (ET) combined with chemical composition analysis reveals the taste quality difference of Keemun black tea (KBT) with natural withering, sun withering and warm-air withering treatments. The results showed that there were significant differences between the taste of the three finished teas, both in sensory and ET evaluation, indicating a stronger bitterness and astringency in the sun withering and a weaker bitterness and astringency in the warm-air withering. The quantitative results of LC-MS and HPLC on the taste compounds indicated that the total amount of catechins in sun withering was 20.85 mg/g, which was 1.90 mg/g and 5.06 mg/g higher than that in natural withering and warm air withering, respectively. This may be because sunlight promotes the conversion of theanine to catechins. The correlation results indicated that there was a quantitative and effective relationship between taste and tasting compounds and that there was a synergistic effect (R ≥ 0.8) between sweet and astringent compounds. This study emphasised a comparative evaluation in methods and in the taste effect of different withering methods, especially providing a theoretical basis for the quality control and flavour improvement of KBT.