The formation of aroma quality of dark tea during pile-fermentation based on multi-omics

Volatile compounds are important contributors to dark tea quality. However, the aroma formation during the key processing pile-fermentation remains unclear. Herein, a total of 46 compounds including 17 alcohols, nine ketones, eight alkenes, five aldehydes, four esters, one heterocyclic oxygen, one alkane, and one pyranoid were identified by GC-MS. At the end of pile-fermentation, alcohols and aldehydes decreased by 21.2% and 12.9% respectively, while ketones and alkenes increased by 40.3% and 11.5% respectively, esters doubled compared to the initial period. PLS-DA analysis demonstrated that the characteristic aroma components were mainly ionone, linalool and its oxides (floral, citrus-like, fruity), safranal (woody, herbal and spice), β-cyclocitral, β-terpinene, limonene (fruity), trans-2-hexenyl hexanoate (fragrance) and roses oxide (rose). Importantly, Pearson correlation analysis demonstrated microbial communities and volatile compounds were highly correlated (|r|>0.7, p