## 3 Results and Discussion
The results of the models constructed for all categories (Table 3) are based on the principle that R2 and Q2 > 0.5 indicate an acceptable model [28], and therefore only models for alcohols and alkanes could be used for the analysis of variance in this result, in which the independent variable fit indices (R2x) were 1 and 1, the dependent variable fit indices (R2y) were 0.997 and 0.998, and the model prediction indices (Q2) were 0.992 and 0.994, respectively. After 200 replacement tests, the intercept between the Q2 regression line and the vertical axis is less than zero, indicating that the model is not overfitted and showing the validated model (Figure 3). Therefore, the result of this research concluded that the modeling results could be significant for key aroma components in green tea. Variable Importance Projection (_VIP_) is usually used for the evaluation of the importance of variables in the OPLS-DA model, the larger _VIP_ value indicating that the aroma substance are more important in the analysis of differences between green tea samples, and it is generally considered that variables with _VIP_ > 1.0 make a higher contribution to the differentiation of the samples [29]. As shown in Figure 4(A1,B1), 10 key aroma substances were screened based on _VIP_ > 1 and \(p\) < 0.05. Based on the distribution map, the key aroma substances can be analyzed for differences between different green tea, where compounds clustered together indicate that they are present in higher amounts in one tea than others, or present only in a certain tea [30]. Different aromas of a variety of teas are attributed to the various types of tea processing. However, various processing strategies determine the extent to which different precursor substances associate in the reactions of degradation process [27]. As shown in Figure 4 (A2,A3), Kaishan white tea 1 and 2 were located in the fourth quadrant with benzyl alcohol and phenylethylanol, and Kaishan white tea 2 was located in the second quadrant with 1-Propoxyhexane, which indicated that benzyl alcohol, phenethyl alcohol, and 1-Propoxyhexane were the characteristic aromas of Kaishan white tea. Green tea is a non-fermented tea, rich in tea polyphenols and other functional components. Tea polyphenol content significantly affects the taste of green tea wine, while alcohol content also affects the extraction of tea polyphenols [31; 32]. Therefore, this research investigated the effect of alcoholic fermentation on tea polyphenols. As shown in  
Figure 3: Cross-validation of OPLS-DA model. Alcohol (**A**), and Alkane (**B**). \begin{table}
\begin{tabular}{l l l l l} \hline \hline  & **R2X** & **R2Y** & **R2** & **Q2** \\ \hline Alcohol & 1 & 1 & 0.997 & 0.992 \\ Ester & 1 & 0.25 & 0.234 & 0.0716 \\ Aldehyde & 1 & 0.75 & 0.488 & 0.338 \\ Oxygen heterocyclic and & 1 & 0.625 & 0.564 & 0.321 \\ Sulfo-compounds & 1 & 1 & 0.998 & 0.994 \\ Hydrocarbons & 1 & 0.625 & 0.58 & 0.349 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: OPLS-DA analysis of each species. Figure 5, tea polyphenol content increased in green tea wine compared to green tea juice, with the highest in Kaisan white tea 3 at 3.72%, an increase of 32.38%. Kaishan white tea 1 had the highest alcohol content and the corresponding lowest residual sugar content of 14.50% vol and 12.45 \({}^{\circ}\)Brix, respectively. Fermentation of fruit wines are a biochemical process in which yeast converts sugars into alcohol and secondary metabolites. Sugar and alcohol content can reflect the fermentation level of fruit wines, while tea polyphenol is an important flavor-presenting substance in tea wine [32]. Kaishan white tea 2 did not have the highest tea polyphenols and alcohol content (3.48 and 14.2% vol), but its indexes were in line with the requirements for fruit wines, and it had the highest aroma content. Therefore, Kaishan white tea 2 was chosen as the best fermented tea base in this study. Figure 4: _VIP_ value, scores and loading plots of OPLS-DA modelof Alcohol (**A1-A3**), _VIP_ value plot, scores plot and loading plot of Alkane (**B1–B3**).