Multi-omics and enzyme activity analysis of flavour substances formation: Major metabolic pathways alteration during Congou black tea processing

To comprehensively analyse flavour substance formation in Congou black tea, dynamic changes in non-volatile and volatile compositions and enzymatic activity were analysed. In total, 107 non-volatile and 222 volatile compositions were identified via ultra-high performance liquid chromatography coupled with quadrupole-exactive mass spectrometry (UHPLC-Q-Exactive/MS) and stir bar sorptive extraction-gas chromatography-mass spectrometry (SBSE-GC-MS), and eight metabolic pathways were explored during tea processing. Significant variations in metabolites were observed during processing (P < 0.05), especially in the fermentation stage, including high accumulation of taste and colour substances due to decreased flavonoid synthase activity and elevated oxidase activity. Correlation analysis clarified that the mutual transformation between non-volatile and volatile substances occurs in certain types of processing, including amino acids, amino acid-derived volatiles (AADVs), glycosidically bound volatiles (GBVs), and volatile terpenoids (VTs). Our study provides a detailed overview of the dynamic changes of in flavour substrates and key enzyme activities during Congou black tea processing.