Volatiles profiles and factors affecting absorption of key odorants in Osmanthus black tea

Osmanthus black tea (OBT) is produced by reprocessing black tea while it absorbs the fragrance of Osmanthus fragrans (O. fragrans) and this scenting process is crucial for forming the unique aroma of OBT. In this study, more than eighty volatile compounds of OBT were analyzed by gas chromatography-mass spectrometry (GC-MS) and six compounds, α-ionone, β-ionone, γ-decalactone, dihydro-β-ionone, dihydro-β-ionol, and 6-pentyl-2-pyrone, were identified as the key volatiles of OBT by weighted gene co-expression network analysis (WGCNA) and orthogonal partial least squares discriminant analysis (OPLS-DA). Variations in the amounts of these compounds occurred with different scenting process conditions such as scenting time (ST) and the ratio of flower to tea (RFT) were discussed. In addition, base teas with a high proportion of pekoes produced higher quality OBT by absorbing more key volatile compounds from O. fragrans. Comparing OBTs made from the fast-scenting process (FS) and the traditional scenting process (TS), showed that a higher aroma quality was obtained through repeated scenting rounds of TS. This study provides valuable insights into the volatile compounds and base tea requirements for an effective scenting process and a theoretical basis for improving scenting technology.