## 3 Results and Discussion
### Identification of Aroma-Active Compounds in WRTs with Different Cultivars
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**No**} & \multirow{2}{*}{**Compound \({}^{*}\)**} & \multirow{2}{*}{**Odor Characteristic \({}^{\text{b}}\)**} & \multicolumn{4}{c}{**AI**} & \multirow{2}{*}{**Identification \({}^{*}\)**} \\ \cline{4-7}  & & & **DHP** & & **RG** & & **SX** & **JF** \\ \hline \multicolumn{7}{c}{Class D (sweet)} \\ \hline
1 & Acetophenone & Sweet, floral & 3.4 & 3.2 & 3.2 & 3.2 & MS, RI, O \\
2 & _p_-Cymene \({}^{*}\) & Fragrant and sweet, fresh, & 3.2 & 2.4 & 2.0 & 3.0 & MS, RI, O \\
3 & 6-MethylJ-3-5-heptadiene-2-one & Sweet, coconut reamy & 3.0 & 3.0 & 3.0 & 2.3 & MS, RI, O, S \\
4 & \(\gamma\)-Nonanalactone & Cooconut reamy, sweet, floral & 2.0 & 2.5 & 2.5 & 2.5 & MS, RI, O, S \\
5 & Coumarin & Milk-like, sweet, floral & - & 2.8 & - & 3.0 & MS, RI, O, S \\
6 & 2.2,6-Trimethyl-cyclohexanone & Sweet, cooked rice & - & - & - & 2.8 & MS, RI, O, S \\ \hline \multicolumn{7}{c}{Class E (herbal)} \\ \hline
1 & 3.5-Octadien-2-one & Mushroom-like & 3.0 & 2.8 & 3.0 & 2.8 & MS, RI, O, S \\
2 & 3-Octen-2-one & Herbal, fruity & 2.8 & 2.8 & 3.0 & 2.8 & MS, RI, O \\
3 & Safranal & Herbal, metallic & 2.5 & 2.0 & 2.3 & 1.7 & MS, RI, O \\
4 & Dihydroactinidiolide \({}^{*}\) & Herbal, essential oil & 2.0 & 2.0 & 2.0 & 3.0 & MS, RI, O, S \\ \hline \multicolumn{7}{c}{Class F (others)} \\ \hline
1 & Heptanal & Fatty, green, herbal & 2.8 & 2.0 & 2.6 & 2.8 & MS, RI, O, S \\
2 & Naphthalene \({}^{*}\) & Pungent, earthy & 2.7 & 3.0 & 3.3 & 3.0 & MS, RI, O \\
3 & Dimethyl trisulfide & Sulforous, pickled vegetables & 2.3 & 2.0 & 2.3 & 2.2 & MS, RI, O, S \\
4 & (_E_,_E_)-2,4-Heptalen & Fatty, slight pungent, green & 2.0 & 3.3 & 3.7 & 2.3 & MS, RI, O, S \\ \hline \hline \end{tabular}   
oolong teas, which frequently present a typical floral scent [1; 31]. Notably, some odorants, such as indole (1.0\(-\)2.5), methyl salicylate (2.4\(-\)3.3), 2,5-dimethylpyrazine (2.4\(-\)3.2), and \(p\)-cymene (2.0\(-\)3.2), had obvious gaps in the AI values among different WRTs. Moreover, some odorants could only be detected in at most two types of WRTs, e.g., 2-methyl-3,5-diethylpyrazine (nutty) could be detected in the SX and DHP samples, coumarin (milk-like, sweet, floral) could be detected in the other two WRTs, and 2,2,6-trimethyl-cyclohexanone (sweet, cooked rice) was only detected in the JF sample. These compounds may be potential odorants that reflect the aroma characteristics of WRTs from different cultivars. 2-Methyl-3,5-diethylpyrazine has been proven to be the key odorant responsible for the special roasted and caramel-like aroma of DHP tea [17]. Coumarin has been reported as the odorant of Jingshan cha and Longjing green teas [32; 33], while it was firstly recognized as the aroma-active compound in oolong teas. However, because of the inevitable sensory errors caused by olfactory sensitivity differences and subjective influences from different panelists, a comprehensive analysis of the GC-O/MS and stoichiometry results was necessary, and the compounds recognized as both key differential VFCs and aroma-active compounds were further analyzed.