## 3 Results and Discussion
### Minor Volatile Compounds  
Table 3 lists the contents of wines in 32 minor volatiles and their homogeneous groups (HGs), with a significance level of \(p\leq 0.05\). The results of the two-way ANOVA are also shown to determine the effect of yeast or additive and their interaction on the content of each compound. These compounds include 5 higher alcohols, 15 esters, 4 aldehydes, 1 ketone, 2 lactones, and finally 5 terpenes and nor-isoprenoids, all of which are largely influenced by the dominant yeast strain at each stage of the fermentation process [41; 42]. Among these 32 quantified minor volatiles, 28 showed significant differences in their concentrations depending on the type of inoculation used for fermentation, and only hexanol, ethyl heptanoate, hexanal, and \(\gamma\)-nonlactone remained unaffected by this factor. In addition, 27 of the compounds were also influenced by the addition of the rich-ONC additive to the must, and only the esters hexyl acetate and ethyl octanoate, together with the aldehyde decanal, were not dependent on the interaction. As mentioned above, the yeast extract added to the must is composed of yeast cell walls and autolyzed yeast, which increase the content of the medium and long-chain fatty acids in the must. Several compounds listed in Table 3, such as aldehydes and alcohols with six carbon atoms and nonanal, are related to the oxidative degradation of fatty acids, while some carboxylic acids and \(\gamma\)-lactones (\(\gamma\)-nonlactone, \(\gamma\)-declactone) are related to the degradation of fats [43]. Also, the enrichment in amino acids, provided by the added extract, plays an important role in wine quality because they are precursors of some aroma compounds through deamination or decarboxylation reactions [44]. The high content of esters such as isoamyl acetate or hexyl acetate in wines preserves their fruity character over time due to their interaction with yeast cell walls, which reduces their loss [45]. The results obtained in our study show a remarkable increase in these compounds, together with 2-phenylethylal acetate and ethyl hexadecanoate, when the yeast extract is added to the must and fermented with AGGLO  
Figure 2: Biplot of the Principal Component Analysis (PCA) performed on the content of major volatiles and polyols. The coordinates of the bold circles indicate the contribution of each compound to each PC. Different shapes group the results of the wine samples on PC1 and PC2. Abbreviations of wines obtained by fermentation with WY: wild yeast; WY + Act: the same with the addition of an activator; AGGLO: Levulia® AGGLO yeast; AGGLO + Act: the same with the addition of an activator. yeast. This increase in ester content confirms the results obtained by other authors after the addition of different yeast extract derivatives to the must [43; 45]. The contents of higher alcohols listed in Table 3 for WY wines do not show significant differences compared to those of WY + Act, except for ethyl-1-hexanol, whose content is higher in WY. On the other hand, when the fermentation is carried out with the agglomerant yeast AGGLO, the levels of these compounds increase significantly in the AGGLO + Act wines, showing the different effect of this additive on the different types of inoculation tested and also indicating a high degree of specificity with the yeast strain [46]. At this point, it is crucial to note that the concentration of higher alcohols significantly influences the taste of the wine. When their content is below 400 mg L\({}^{-1}\), they contribute to a fuller and rounder wine, enhancing its flavor. However, if their concentration exceeds this threshold, a distinctive off-flavor similar to that of organic solvents may emerge, which negatively impacts the wine's quality [47]. The statistical analysis performed on the aldehyde, ketone, and lactone contents, shows that they are all grouped in three HGs, except for \(\gamma\)-nonalactone, in four HGs.