Dynamic changes of volatile, β-glucosidase enzyme activity and regulatory gene expression during the processing of Wuyi black tea

Wuyi black tea (WBT) is the origin of black tea, with a history of over 4 centuries. Headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography–mass spectrometry (GC-MS) was employed to investigate the dynamic changes of volatile compounds. And, the contributions of β -glucosidase and key genes underlying the aroma formation were also illuminated. Totally, 94 volatile compounds were detected in WBT processing. Except for heterocyclic compounds and aldehydes, other volatile categories reached the peak at withering. Most of characteristic volatile compounds are accumulated during the withering or rolling stage. Therefore, withering and rolling are assumed to be key bases for the aroma formation. Interestingly, the content variation of several characteristic volatile compounds such as ( Z,E )- α -farnesene, and total alcohols was basically in accordance with that of the β -glucosidase enzyme activity. Besides, aroma-related genes including β-glucosidase 1 (BG1), 3-hydroxy-3-methylglutaryl-Co A Reductase (HMGR), germacrene D synthase (GES), nerolidol synthase (NES) and 3-hydroxy-3-methylglutaryl-Co A synthase (HMGS) showed similar expression patterns. Their expression levels were found to be upregulated in F8, with NES exhibiting a remarkable 350-folds increase. During withering, the expression of β-glucosidase 2 (BG2) , linalool synthase (LIS) and α-farnesene synthase ( AFS) was induced by drought stress. Notably, AFS and BG2 demonstrated stronger correlations with volatile variations than other 6 genes. Collectively, our study establishes a theoretical guidance for producing high-aroma WBT. • Volatile compounds, β -glucosidase and gene expression were simultaneously analyzed during WBT processing. • AFS and BG2 showed stronger correlations with volatile variations than other 6 genes. • (Z,E )- α -farnesene change was completely consistent with β -glucosidase enzyme activity. • Expression levels of BG1 , HMGR , GES , NES and HMGS were significantly upregulated in F8.