How Do Green-Leaf and Yellow Tea Cultivars Influence Black Tea Flavor? Insights from Metabolomic Analysis with...

To elucidate the metabolic mechanisms underlying black tea flavor formation driven by cultivar genotype and processing technology, two cultivars, the green-leaf "Ningzhou No. 2" and the yellow-leaf "Huangjinju", were processed via the traditional Ningzhou Gongfu black tea manufacturing protocol. Ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS)-based widely targeted metabolomics was employed to compare the metabolites and main biochemical components in fresh leaves, combined with the sensory evaluation of processed black tea from Camellia sinensis cv. "Huangjinju" and "Ningzhou No. 2". The results showed that a total of 2208 metabolites were detected, representing 25 classes, including flavonoids, phenolic acids, terpenoids, esters, amino acids and their derivatives, and alkaloids. The characteristic differential metabolites in the fresh leaves from the two cultivars were primarily flavonoids. After processing, "Huangjinju" exhibited a relatively higher content of terpenoids, whereas "Ningzhou No. 2" showed relatively higher levels of flavonoids and phenolic acids. "Huangjinju" excelled with the Ningzhou Gongfu method, emphasizing floral notes and a liquor color, a sweet and mellow taste, and spent leaves, yielding a richer sweet-floral profile with nutty undertones and a reddish liquor. Cultivar primarily influenced bitterness, while processing modulated floral, fruity, nutty, sweet, and off-flavors. Metabolic enrichment analysis revealed cultivar-specific differences in fatty acids, terpenoids, heterocycles, and flavonoids, aligning with sensory profiles. These findings provide a metabolic basis for optimizing Ningzhou Gongfu black tea processing and quality control. KEGG pathway enrichment analysis further identified that galactose metabolism was a key pathway underlying the metabolic differences between the black teas of the two cultivars. Metabolic differences between the two tea cultivars determined the quality and processing suitability of fresh leaves. During the processing of black tea, chlorophyll content is significantly reduced, and the higher the chlorophyll content in fresh tea leaves, the more capable they are of forming the quality characteristics of red tea soup and red leaves. Metabolic profiles undergo extensive transformation, and cultivar characteristics influence the efficiency and direction of these transformations. Yellow tea tree varieties can also be made into high-quality black tea. These findings provide new insights and supporting data for the precise utilization of the two tea cultivars and the quality control of black tea.