## 4 Discussion
### Dynamic Changes in VBs/VPs in Oolong Tea Products
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Types**} & \multirow{2}{*}{**Component**} & \multirow{2}{*}{**CAS**} & \multirow{2}{*}{**Character**} & \multicolumn{2}{c}{**Concentration**} & \multirow{2}{*}{**OAV**} & \multicolumn{2}{c}{**Threshold**} \\  & & & & (ug/g) & & & **(ug/kg)** \\ \cline{5-8}  & & & & **Rt** & **Rc** & **Rt** & **Rc** & **-** \\ \hline \multirow{4}{*}{VPs} & Phenylethyl alcohol & 60-12-8 & Rose-like & 197.89 \(\pm\) 6.10 & 64.71 \(\pm\) 6.80 & 5.81 & 1.90 & 750 \\  & Methyl phenylacetate & 101-41-7 & Sweet floral & 23.59 \(\pm\) 4.17 & 24.05 \(\pm\) 3.37 & 0.52 & 0.53 & 1000 \\  & Phenethyl acetate & 103-45-7 & Rose-like & 10.69 \(\pm\) 0.15 & 3.45 \(\pm\) 0.07 & - & - & - \\ \hline \hline \end{tabular}
\end{table} 
Table 3: _Cont._the only VP that was not significantly correlated with all _CsAAAT_ genes, which might indicate a relationship between the formation of this substance and the PAAS branch, rather than the AAAT branch. There was a generally strong positive correlation between VBs and key _CsAAAT_ genes, suggesting a convergence effect in the formation of VBs both in the PAL and AAAT branches during the post-harvest process of oolong tea. This result agrees well with previous studies. For example, [PERSON] et al. (2018) reported the expression patterns of _CsAAAT_ genes under pre-harvest treatment of fresh tea leaves. There was no significant change in the expression level of _CsAAAT1_-type genes during solar-withering, but the expression levels of three _CsAAAT2_-type genes in SW were significantly higher than those in F, indicating that the _CsAAAT1_ gene might be dominant in response to mechanical stress caused by turnover, while the _CsAAAT2_ gene may respond to not only mechanical stress but also light and heat stress caused by solar-withering treatment. This is basically consistent with the viewpoint proposed by [PERSON] (2021) that \"yellow light treatment could promote the metabolism of VBs/VPs during the spreading treatment, a process similar to solar-withering, which enhanced the formation of high aroma quality of green tea\" ([PERSON] et al., 2016). Furthermore, our results are similar to those reported by [PERSON] et al. (2016), who found that \"the petals of roses activate AAAT to catalyze L-phe synthesis of phenylpyruvate under high temperature stress in summer\" ([PERSON] et al., 2016). The low sensitivity of _CsAAAT1_-type genes to temperature might be related to the spatial expression differences in this type of gene. Therefore, we speculated that the expression abundance of _CsAAAT1_-type genes might be lower than that of _CsAAAT2_-type genes under heat stress during the post-harvest process of oolong tea. After the turnover treatment, VBs/VPs changed and volatilized under green-killing and rolling treatments, and finally, only four types of VBs and three types of VPs were left in the raw oolong tea. Interestingly, benzoic acid, 2-hydroxy-, pentyl ester was only identified in Rt, indicating that after drying, the VB components in the tea leaves were still changing and forming through non-enzymatic conversion, which would eventually contribute to the aromatic quality of oolong tea, to some extent. These results are in line with those of a previous study ([PERSON] et al., 2016), wherein short-term solar-withering facilitated the accumulation and release of volatile components. As for benzyl alcohol, phenyl ethanol, and methyl salicate, these components all contributed to a long-lasting floral fragrance in Rt, similar to previous studies.