## 2 Results and Discussion
### Odor activity values (OAVs)  
Though dozens of volatiles were detected in each wine sample, not all of the components have the same impact on the overall aroma character of a wine. Of all the compounds analyzed, only those displaying OAVs greater than 1 were deemed to contribute to wine aroma [30]. The contribution of each volatile compound with OAVs above 1 to the aroma of each wine can be evaluated qualitatively by means of its associate descriptor, and quantitatively by means of its OAVs. Table 2 listed the OAVs for the 18 odor-active compounds (OAV \(>\) 1 in at least one of the wines studied), Chardonnay and Cabernet Sauvignon wines had the same odorants with OAVs above 1, and \begin{table}
\begin{tabular}{l l l l l} \hline
**Compounds** & **Odor descriptor** & **Cabernet** & **Cabernet** & **Chardonnay** \\  & & **Sauvignon** & **Gernischet** & \\ \hline Ethyl octanoate & Pineapple, pear, floral & 2554.0 (61.4\%) & 2142.0 (62.7\%) & 6883.9 (77.0\%) \\ Ethyl hexanoate & Fruity, anise & 821.4 (19.7\%) & 597.0 (17.5\%) & 1107.1 (12.4\%) \\ Isoamyl acetate & Banana & 491.1 (11.8\%) & 446.7 (13.1\%) & 828.3 (9.3\%) \\
2-Octanol & — & 202.3 (4.9\%) & — & — \\ Nonanal & Green, slightly & 49.0 (1.2\%) & 69.9 (2.0\%) & 18.5 (0.2\%) \\ \(\beta\)-Ionone & Violet & — & 64.4 (1.9\%) & — \\ Isovaleric acid & Fatty, rancid & — & 58.7 (1.7\%) & 26.9 (0.3\%) \\ Ethyl decanoate & Fruity, fatty, pleasant & 7.3 (0.2\%) & 7.6 (0.2\%) & 39.8 (0.4\%) \\ Octanoic acid & Rancid, harsh, cheese & 10.4 (0.2\%) & 7.7 (0.2\%) & 22.4 (0.3\%) \\ Heptyl acetate & Almond, pear & 10.1 (0.2\%) & — & 4.1 (\(<\)0.1\%) \\ Ethyl acetate & Fruity, sweet & 7.0 (0.2\%) & 9.3 (0.3\%) & 4.4 (\(<\)0.1\%) \\ Isoamyl alcohol & Cheese & 6.2 (0.1\%) & 4.8 (0.1\%) & 3.4 (\(<\)0.1\%) \\
3-(Methylthio)-1-propanol & Boiled potato, rubber & 4.0 (0.1\%) & 4.0 (0.1\%) & — \\ Decanal & — & — & 2.2 (\(<\)0.1\%) & — \\
1-Dodecanol & Orange flowery, special fatty & 0.9 (\(<\)0.1\%) & 1.8 (\(<\)0.1\%) & — \\ Ethyl dodecanoate & Flowery, fruity & 0.2 (\(<\)0.1\%) & 0.2 (\(<\)0.1\%) & 1.4 (\(<\)0.1\%) \\
2-Phenylethanol & Flowery, pollen, & 1.0 (\(<\)0.1\%) & 1.3 (\(<\)0.1\%) & 0.7 (\(<\)0.1\%) \\  & perfume & & & \\ Phenethyl acetate & Pleasant, floral & — & 0.1 (\(<\)0.1\%) & 1.2 (\(<\)0.1\%) \\ \hline \end{tabular}  
* OAVs were expressed as the mean concentration of an aroma compound divided by its odor threshold value;
* ROC of each aroma compound shown in parentheses was calculated as the ratio of the OAV of the individual compound to the total OAV of each wine.  
\end{table} 
Table 2: Odor activity values * (OAVs) and relative odor contribution * (ROC) for the aroma compounds in Cabernet Sauvignon, Cabernet Gernischet, and Chardonnay young wines. in contrast, Cabernet Gernischet wine contained the most odor-active compounds, suggesting that the Cabernet Gernischet wine presented more complex flavor than the others. In addition, the OAVs for ethyl octanoate, ethyl hexanoate and isoamyl acetate in Chardonnay wine were close to two times higher than those of Cabernet Sauvignon and Cabernet Gernishcet wines. The computation of relative odor contribution (ROC) proposed by [PERSON] [31] is a useful index for determining the important aroma components in a complex system. Based on the ROC values of single compound, we found that the global aroma of all three wines was dominated by fermentative aromas, namely, the ethyl esters of fatty acids that conferred fruity notes to all the wines. Specifically, ethyl octanoate, ethyl hexanoate, and isoamyl acetate jointly accounted for 92.9%, 93.3%, and 98.7%, of the global aroma of Cabernet Sauvignon, Cabernet Gernischet and Chardonnay wines, respectively (Table 2). The results in this study were partially consistent with the results in a previous study [8] showing that the three aroma compounds mentioned above jointly accounted for 97% and 99%, respectively, of the global aroma of Cabernet Sauvignon and Cabernet Gernischet wines from Huailai County of China.