Elucidation of flavor formation in Congou black tea: the role of drying temperature

This study employed headspace solid-phase microextraction/ solvent-assisted flavor evaporation combined with gas chromatography-mass spectrometry (HS-SPME/SAFE-GC-MS) and liquid chromatograph-mass spectrometer (LC-MS) to analyze volatile and non-volatile compounds of Congou black tea under different drying temperatures. The results demonstrated that 90RF (rough-fired) maximised floral/green aroma and umami taste. In contrast, 130RF enhanced fruity/roasted aromas with minimal astringency. Regarding over-fired drying, 60OF (over-fired) produced the highest umami taste, 75OF significantly enhanced floral aroma, whereas 90OF intensified fruity and sweet aromas and minimized astringency/bitterness. Analysis of key volatile compounds revealed that the pronounced floral and green aroma could be attributed to the high concentrations and the relative aroma characteristic impact (rACI) values of ( E,E )-2,4-heptadienal and ( Z )-3-hexen-1-ol. Simultaneously, the intensified fruity and sweet aroma was associated with an increased abundance of β -damascenone. Furthermore, analysis of non-volatile metabolites in conjunction with a correlation analysis of taste attributes, revealed that amino acids, flavonoids (along with their glycosides), and phenolic acids were the primary constituents responsible for the observed differentiation in taste among the samples. This study showed 75 °C and 90 °C over-fired drying as the optimal condition for floral, fruity and sweet aromas intensity respectively, which offers a targeted approach for Congou black tea process control. • 1.Drying temperature plays critical role in shaping flavor profile of Congou black tea. • 2.High-temperature drying enhances floral and sweetness aroma and reduces astringency. • 3.High-temperature reactions of amino acids and flavonoids induce flavor transformation.