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

Abstract

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 < 0.05). Candida, Debaryomyces, Cyberlindnera and Penicillium had high positive correlation with alcohols and ketones. Byssochlamys had high positive correlation with ketones, alkenes, and esters, Rasamsonia had negative correlation with alcohols, ketones, and aldehydes. Thermoascus and Thermomyces had positive correlation with aldehydes. Altogether, this research clarified the relationship between microbial communities and aroma formation during pile-fermentation and demonstrate a theoretical basis for improving the aroma quality of dark tea by controlling microbial communities.