## 3 Results
### Volatile Compounds
The change along PC2, which mainly involved V2, was then associated to a decrease over time of hexanal (R.t. 10.46 min) and 2-hexenal (R.t. 15.90 min), with an increase of their correspondent alcohols: _n_-hexanol (R.t. 21.84 min) and 2-hexen-1-ol (R.t. 24.14 min), respectively. The occurrence of C6 aldehydes and the corresponding alcohols in wines was related to \"leafy/grassy\" and \"herbaceous\" aromas, typical from fresh-cut vegetal tissues [55]. These compounds are originated enzymatically by the activity of lipoxygenases through the oxidation of linoleic and linoleic acids present in the cell wall membranes of the grape skin before fermentation [21; 56]. Levels of C6 aldehydes and alcohols in grapes depend upon the grape variety, the ripeness stage of grapes, treatment of the must, and time and temperature by which the must is kept in contact with the skin, which is the main difference between V1 and V2. During the vinicination, these compounds were shown to change due to the chemical reduction of the aldehydes into their corresponding alcohols (which have a higher perception threshold) by the alcohol dehydrogenase of the yeast and to the esterification of the alcohols undertaken by the yeast esterase [57]. This appears to have impacted particularly V2 samples. The samples collected between the beginning of the fermentation and the bottling (T5-T12) were evaluated with a PCA model as well (Figure 2C,D), which was built separately from the previous samples (T1-T4), for the reason reported above for phenolic compounds. As seen earlier, the variability rapidly increased after T7 and no trend across the initial samples (T1-T4) could be observed, if analyzed together with T5-T12 samples (data not shown). The PC1 vs. PC2 scores and loadings for the samples collected after the beginning of the fermentation are reported in Figure 2C,D. The score plot showed again a separation between V1 and V2. Interestingly, the separation was obtained again along PC1, indicating that the vinicination was the main factor influencing the samples variability, with a smaller effect of the temporal trend observed within each vinicitation, parallel to PC1 this time, indicating that the main variables affected by the different vinicitation were also causing the evolution of the wines overtime. In fact, the loading plot in Figure 2D shows that the separation in PC1 is mainly caused by the linear ethyl esters and the acetate esters, contributing mostly in V1, and higher alcohols contributing mostly for V2. Noticeably, trends in the T5-T12 PCA Score Plot (Figure 2C) were observed in relation to some classes of volatile compounds. Most branched esters, carboxylic acids (octanoic acid and acetic acid) acetate esters and the linear ethyl esters (with the exception of ethyl butanoate, R.t. 8.92 min) contributed mainly to V1 in PC1. In addition, several groups of volatile compounds associated to a chemical class were observed, even if not specifically associated to one factor or trend. All alcohols were identified at high positive values of PC2 with a negligible but still higher contribution in V2 wines than in V1 (phenylethyll alcohol and n-hexanol, R.t. 43.72 and 21.84 min, respectively). Finally, the results of the PCA performed on the V1 and V2 samples at W0 (at bottling), W3 (three months after bottling), W6 (six months after bottling) and W9 (nine months after bottling) are presented in Figure 2E,F. Differently from what was seen with the previous samples, here the wider separation among the observations (Figure 2E) along PC1 was driven by the separation of V1.W9 samples from all the others. A separation between V1 and V2 samples was still present but not clearly defined along one specific PC. Consequently, all samples V1 and V2 were found at lower scores in PC1 than V1.W9. V1.W9 was separated from both V1.W6 and V2.W9 along PC1. Notably, most of the variables were now drawn towards high positive values of PC1, indicating that the volatiles evolution was more accelerated after nine months in V1 than in V2.