## 3 Discussion
### Influence of Grape Withering on Volatile Composition of Corvina Wines
C\({}_{6}\) alcohols were also found to discriminate, with a high level of significance, control wines from the two withering modalities. C\({}_{6}\) alcohols contribute to the \"leafy\" and \"herbaceous\" odors of wines [32]. In control samples _cis_-3-hexenol showed and odor active value (OAV, calculated as ration between concentration and odor threshold) higher than one therefore potentially contributed to wine aroma (OAV = 1.3). Instead, in withered samples, the C\({}_{6}\) alcohols had OAV values lower than one. C\({}_{6}\) alcohols are formed during berry crushing by enzymatic oxidation of grape unsaturated fatty acids, initiated by grape lipoxygenase enzymes [33]. [PERSON] et al. (2016) [17] reported a decrease in the expression of lipoxygenase genes during withering of Corvina, which could explain the decrease in C\({}_{6}\) alcohols observed here. However, other studies indicated an opposite trend [8; 16], an increase in C\({}_{6}\) aldehydes and alcohols during postharvest grape dehydration of Malvasia grape was reported [8], suggesting that more complex patterns could occur. Various terpen were affected by withering, although trends varied depending on the specific molecule. The importance of monoterene alcohols and cyclic terpen to Corvina wines aroma was recently described, in particular for linalool [34; 35]. In the present study, linalool was the main monoterene alcohol detected and its concentration was significantly decreased by withering, in agreement with previous findings [17; 36]. Considering that in control wines linalool had an OAV\(=1.1\), a possible contribution to wine aroma characteristics can be expected, whereas in wines from witnessed grapes this was not the case (OAV = 0.59 and 0.66 for fruttaio and on-vine respectively). Terpenes are produced in grapes through both the 1-deoxy-p-xylulose-5-phosphate/methylerythritol phosphate (DOXP/MEP) pathway and the mevalonic acid (MVA) pathway. In Corvina the influence of withering on these pathways is complex, with upper steps of the pathway being downregulated but late biosynthetic steps upregulated [16]. In addition to free forms of terpen, grapes also contain non-volatile glycosylated forms of these compounds, which in Corvina can contribute significantly to terpen level in finished through enzymatic and chemical hydrolysis during vinification [35; 37]. Although in the present study differences in glycosidically-bound terpen in the finished wines were relatively small, we observed generally higher concentrations of bound terpen in withered wines (Table 2). Contrary to linalool, citronellol, the second most abundant monoterpene alcohols detected, increased with withering. In non-aromatic grapes such as Corvina, formation of citronellol is connected to the ability of yeast to reduce available geraniol including the portion derived from hydrolysis of geraniol glycosidic precursors [37; 38]. Bound geraniol in finished wines increased in one of the withering modalities, supporting a possible contribution of bound geraniol to free citronellol levels. In wines from withered Pinot nor, [PERSON] et al. (2008) [9] also observed increased wine citronellol content. Among other terpen, withering was consistently associated with increased contents of linalool oxides, limonene and 1,4-cineole. Small increases in the content of terpinen-4-ol in wine were also observed with withering, in agreement with the observations of [PERSON] et al. (2016) [17]. The contribution of linalool oxides, limonene, 1,4-cineole and terpinen-4-ol to wine aroma seemed to be limited because their concentrations were found to be lower than the respective odor thresholds. norisoprenoids such as 3-oxo-\(\alpha\)-ionol had an opposite behavior and were found in higher concentrations in withered samples. The benzenoids ethyl vanillate, and benzyl alcohol were found in higher concentrations in withered samples, unlike previously reports by [PERSON] et al. (2016) [4], albeit with more intense withering.