Integrating metabolomics and electronic tongue analysis to reveal the dynamic evolution of taste metabolites during industrial black tea processing: A temporal clustering approach

Black tea, produced from Camellia sinensis , possesses a distinct flavor profile developed through complex processing steps. However, the specific metabolic mechanisms driving taste evolution remain insufficiently understood. This study employed a constituent–taste relationship strategy to identify key taste-related metabolites during industrial processing. Fresh leaves and samples from five subsequent stages were comprehensively analyzed using Ultra-Performance Liquid Chromatography-Quadrupole Time-of-Flight Mass Spectrometry (UPLC-QTOF-MS/MS), while electronic tongue profiling was specifically applied to the fresh leaves and the final product to establish taste benchmarks. Results showed significant increases in sweetness, saltiness, and bitterness, contrasted by a decline in umami from fresh leaves to the final product. While simple catechins were highest in fresh leaves, theaflavins peaked during the intermediate stage. Sixty-five metabolites—including amino acids, catechins, flavonoids, nucleotides, and phenolic acids—showed strong correlations with taste attributes. Temporal clustering revealed that the rolling and drying stages were the most critical phases, exhibiting the most significant metabolic fluctuations. Pathway analysis further identified the accumulation of amino acids and the formation of polymeric catechins as central drivers of flavor formation. These findings elucidate the metabolic basis of black tea flavor, providing a scientific foundation for optimizing industrial processing techniques.