Aromatic markers and differences between green and oolong teas: insights from 31 representative cultivars

Oolong and green teas are two types of tea with distinct aroma characteristics primarily shaped by their processing methods; yet, the influence and contribution of cultivar differences remain insufficiently understood. This research applied headspace solid-phase microextraction combined with gas chromatography–mass spectrometry (HS-SPME-GC-MS) to identify 239 volatile compounds in fresh leaves of 15 green tea (GT) and 16 oolong tea (OT) cultivars. These cultivars, originally bred in various provinces, were cultivated under uniform conditions in a tea germplasm resource garden in Fujian Province. Principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) showed a clear separation between GT and OT. Using the criteria of variable importance in projection (VIP) > 1 and p < 0.05, 112 volatile compounds with significant differences were identified. Among them, E,Z-2,6-dimethylocta-2,4,6-triene and geranyl isovalerate were detected at significantly higher levels in OT, with the highest concentrations observed in 'Mingke 1'. Relative odor activity value (rOAV) analysis combined with random forest analysis revealed that key compounds in GT included nonanal, Z-jasmone, 2,6-dimethyl-1,7-octadiene-3,6-diol, linalool, nerol, and 1-decanol. This study analyzed the volatile component variation between GT and OT cultivars, providing a reference for breeding tea cultivars with distinct processing suitability.