Metabolomics reveal taste quality differences of black teas and the impact of withering on quality formation.

Taste is one of the important factors for evaluating the quality of tea. Smart tongue and metabolomics were used to analyze the difference in taste of Gongou black teas from three different varieties. In this study, 564 non-volatile metabolites (NVMs) were identified in the black teas. The quality difference between Shuyong 3 black tea (SY-T) and Fuding Dabai black tea was the greatest, followed by SY-T and Sichuan Small and Medium-leaf black tea. Specially, the differential NVMs primarily influenced the astringency, sourness, umami, and bitterness taste attributes of black teas, rather than sweetness. Based on the correlation results between differential NVMs and the taste of black tea, and in combination with the VIP value ≥ 1.5, 24 characteristic differential NVMs that might have a significant impact on the formation of different taste qualities were successfully screened out. In the withering process, the differential metabolic pathways of three different varieties were primarily concentrated in flavonoid and carbohydrate metabolic pathways, which was potentially explaining the main cause of alterations in the characteristic metabolites and the taste profiles of the black teas. Our findings provide a theoretical basis for the taste variations among different varieties, as well as a new insights into the quality formation of black tea during the withering process.