Multi-omics combined with simulated fermentation model for elucidation of variation patterns of lipids and volatiles and its mechanism during black tea fermentation.

Lipid metabolism and fatty acid-derived volatiles (FADVs) are crucial in black tea aroma formation. Herein, dynamic variations of 458 lipids and 59 volatiles during black tea fermentation were investigated by multi-omics using UHPLC-Q-Exactive/MS and GC-MS. 120 lipids and 27 FADVs were predominantly altered during fermentation. Glycerophospholipids and glycoglycerolipids harboring 18:2 and 18:3 fatty acyls were highlighted as potential aromatic precursors. Model experiments using linoleic acid revealed firstly that both non-enzyme auto-oxidation and enzyme oxidation participated in FADVs formation. 28 FADVs were generated at an abundance of 156.01 μg/L by non-enzyme oxidation. Whereas, 32 FADVs with an abundance of 215.01 μg/L were produced in simulated fermentation system containing crude enzyme, covering fatty aldehydes, esters, ketones, alcohols, furans, etc. Specifically, 9 FADVs exhibited odor activity value >1 in simulated fermentation, e.g., hexanal, 2-pentanone, heptanal, 2-pentylfuran, mainly imparting fresh, floral, fruity notes. This study provides novel insights into black tea aroma formation.