Unlocking the metabolic code of Qingzhuan tea from fresh leaves to finished product: Insights into flavor evolution at an industrial scale.

Qingzhuan tea (QZT) acquires distinctive sensory and functional properties, but the quality evolution during lengthy industrial processing remains unclear. Therefore, this study deciphers the flavor evolution mechanisms by analyzing non-volatile dynamics from fresh leaves to finished tea. A total of 821 metabolites were identified, with 136 differential metabolites mainly comprising lipid degradation and flavonoids polymerization potentially driving the formation of flavor. De-enzyming (SQ) and pile-fermentation (WD) are the critical steps for the quality formation of QZT. The SQ preserved polyphenols while triggering lipid hydrolysis and phenolic acid conversion, whereas WD catalyzed catechin polymerization, flavonoid glycoside degradation, and caffeine biotransformation to reducing astringency and enhancing sweetness. Further, weighted co-expression network analysis (WGCNA) revealed that flavonoid glycosides and lipids potentially underpinned the transition from light yellow to reddish hues. This study provides the first industrial-scale metabolic profile during the whole processing of QZT, advancing precision control in dark tea production.