## 3 Results and Discussion
### OAV-Based Characteristic Aroma Analysis  
A total of eight varietal aroma components were detected in the wine samples, including four terpenoids, three C6 compounds, and one C\({}_{13}\)-norisoprenoid (Figure S1 and Table S1). Among these, \(\beta\)-damascenone had an OAV > 1 and a potentially large contribution to the floral aroma of the wine samples. Substances with OAV > 0.1 included hexanol, (Z)-3-hexen-1-ol, and geraniol, which influence the aroma of the wines through their interaction with each other (Table S2). As shown in Table S1, among the wines prepared from the five grape varieties in this study, Malbec wines had the most abundant varietal aroma components, while Cabernet Franc and Cabernet Sauvignon, each with only five aroma components, with the lowest abundance of varietal aroma components. In terms of the contents of each type of aroma, Pinot Noir had a significantly higher content of C6 compounds than the other varieties and exhibited a stronger herbaceous vegetal flavor [18]. The contents of terpenoids in the Malbec wine samples from both clones were significantly higher (5-10 times) than  
Figure 1: Proportions of various aroma substances in wine samples. (**A**) Percentage share of each type of aroma having high content. (**B**) Percentage of thousand points for some of the lower content aromas. those in the other wine samples. As shown in Figure S1, in terms of terpenoid content, the Malbec wine samples were outliers because there were no significant differences in terpenoid content between the other varieties. Terpenoids impart floral and fruity aromas to wine [19]. Notably, citronellyl butyrate, and nerol were exclusively detected in the Malbec wine samples. In addition, the geraniol content of Malbec was significantly higher than other varieties. The OAV of geraniol exceeded 0.1, which imparted a rose aroma to the wine samples [20]. There was a significant difference in geraniol content between the two clones of this variety, with Malbec 598 having a geraniol content that was 1.5 times higher than that of Malbec VCR6. However, geraniol was not detected in the Cabernet Franc and Cabernet Sauvignon wine samples. \(\beta\)-Damascenone, a C\({}_{13}\)-norisoprenoids compound, mainly imparts sweet and floral aromas to the wine [21]. Despite being present in minute quantities, \(\beta\)-damascenone, with a low threshold of 0.05 ug/L, is the largest contributor to the overall aromatic composition. There were 19 detected fermentation aroma components with OAV > 0.1, among which ethyl acetate, ethyl butyrate, isoamyl acetate, ethyl caproate, ethyl caprylate, ethyl decanoate, ethyl 9-decenoate, isobutanol, isoamyl alcohol, and isovaleric acid had an OAV > 1 (Table S2). All the fermentation aroma components with an OAV > 0.1 were subjected to PCA. The loadings of fermentation aroma components on the first two main components and the distribution of the samples are shown in Figure 2.  
PC1 and PC2 accounted for 39% and 28%, respectively, of the overall variance. Most of the fermentation aroma components and the three grape clones, viz. Cabernet Sauvignon 170, Cabernet Sauvignon VCR11, and Malbec 598, were distributed at the negative end of PC1. Fatty acids, fatty acid ethyl esters, acetates, most of the higher alcohols, isobutyric acid, Cabernet Sauvignon 15, and Cabernet Sauvignon 169 were distributed in the positive end of PC2. The wine samples from the four Pinot Noir clones were distributed in the fourth quadrant, surrounded principally by 1-butanol and decanal. The other three Cabernet Franc clones, except Cabernet Franc 396, were distributed at the positive end of PC1, close to isobutanol, ethyl lactate, 1-butanol, and decanal. Cabernet Franc 396 was distributed at the negative end of PC2, surrounded by ethyl acetate, ethyl 9-decenoate, and decanal. Merlot VCR1 was distributed in the first quadrant with only isobutanol distributed around it,  
Figure 2: Loadings of fermented and varietal aroma compounds and the distribution of the wine samples in the first two PCs.