Withering-induced lipid metabolism remodeling underpins the formation of tea aroma

Withering is a critical step that influences the formation of tea quality. The dehydration stress during withering induced considerable losses of lipids, which are crucial tea aroma precursors. However, the lipid metabolism and transformation during withering and their impact on tea aroma formation have not been systematically characterized. Herein, through lipidomics and gas chromatography-mass spectrometry (GC-MS) analysis, we found the significant loss of total lipids during withering, primarily driven by the degradation of glycerophospholipids, bis(monoacylglycero)phosphates (BMPs), sphingomyelins (SMs) and monogalactosyldiacylglycerols (MGDGs) containing (18:3) fatty acyl residues, while triacylglycerols (TAGs) and free fatty acids (FFAs) accumulation were activated. The lipid metabolism was remodeled with changes in the unsaturation degree and chain length of acyl chains. Total 271 lipids and 38 volatiles were identified as withering dynamic lipids and withering different volatile compounds, respectively. Through co-expression analysis of lipids and volatile compounds, certain C52/C54 TAGs, FFAs, LPC(16:0), LPE(16:0), and LPG(16:0) were the key lipids or lipid biomarkers for tea aroma formation during withering. Furthermore, withering could promote lipid-aroma formation by activating the expression of CsPLA/CsPLC/CsPLD, CsLOXs, CsHPL1, CsADHs and CsAAT. These findings offer lipid-centric reference data for the improvement of tea quality and the development of standardized tea processing.