# Characterization of the Aroma Profile of Commercial Prosecco Sparkling Wines
## Results and Discussion
### Volatile Compounds in Prosecco Wines
#### 3.2.4 Terpenes and C13-Norisoprenoids  
Terpenes are produced in grapes through both the 1-deoxy-d-xylulose-5-phosphate/m-ethylerythmitol phosphate (DOXP/MEP) pathway and the mevalonic acid (MVA) pathway [17]. The terpenes produced can then be glycosylated in the berry. During fermentation,  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline
**Compound** & **Min** & **Max** & **Mean** & **RSD** & **Asolo** & **Treviso** & **Valdobbiadene** & _p_-Value** \\ \hline  & **(ug/L)** & **(ug/L)** & **(ug/L)** & **(\%)** & **(ug/L)** & **(ug/L)** & **(ug/L)** & \\ \hline
4-Vinylguaiacol & 3.42 & 13.06 & 7.21 \(\pm\) 2.11 & 29.29 & 4.81 \(\pm\) 1.54 a & 7.91 \(\pm\) 1.89 ab & 7.6 \(\pm\) 1.95 b & 0.044 \\ Vanillin & 2.07 & 25.42 & 3.66 \(\pm\) 4.71 & 128.6 & 9.01 \(\pm\) 11.11 a & 2.64 \(\pm\) 0.32 b & 2.59 \(\pm\) 0.33 b & 0.774 \\ Methyl-vamillate & 3.07 & 6.05 & 4.17 \(\pm\) 0.66 & 15.85 & 3.74 \(\pm\) 0.48 a & 4.28 \(\pm\) 1 a & 4.21 \(\pm\) 0.57 a & 0.434 \\ Ethyl-vanillate & 0.49 & 3.08 & 1.77 \(\pm\) 0.58 & 32.95 & 1.64 \(\pm\) 0.89 a & 1.64 \(\pm\) 0.36 a & 1.82 \(\pm\) 0.58 a & 0.85 \\ Methyl salviolate & 0.31 & 6.69 & 3.39 \(\pm\) 1.39 & 41.03 & 4.23 \(\pm\) 1.65 a & 2.49 \(\pm\) 1.27 a & 3.42 \(\pm\) 1.28 a & 0.246 \\ Benzaldehyde & \(<\)LOQ & 11.82 & 5.04 \(\pm\) 4.06 & 80.52 & 0.94 \(\pm\) 0.82 a & 4.37 \(\pm\) 3.77 a & 6.18 \(\pm\) 4 a & 0.013 \\ Sum of & 13.41 & 45.23 & 25.24 \(\pm\) 7.81 & 30.95 & 24.36 \(\pm\) 14.53 a & 23.34 \(\pm\) 7.07 a & 25.82 \(\pm\) 6.2 a & 0.537 \\ \hline \end{tabular}
\end{table}
Table 3: \(Cont.\)these bound forms are then cleaved by the yeasts releasing the aglycone [18]. Terpenes are an important contributor to floral and citric notes and are found in higher concentrations in aromatic varieties such as Muscat [19; 20]. Even if Clera is not a grape variety considered aromatic, a large number of terpenic molecules were identified and quantified in the analyzed wines. Among these terpen, the one found in higher concentration was linalool, followed by \(\alpha\)-terpineol, and linalool oxide. One sample showed a much higher content compared with the others, about 88 \(\mathrm{\SIUnitSymbolMicro g}\)/L, which was much higher than the odor threshold of 25 \(\mathrm{\SIUnitSymbolMicro g}\)/L. A wide variability in terpene concentration was observed between the various samples, with differences between minimum and maximum of up to two orders of magnitude. This diversity could be due to various agronomic, viticultural and geographical factors [12; 21; 22; 23].  
Due to their low odor threshold, C\({}_{13}\)-norisoprenoids are very powerful odor compounds. The 3-oxo-\(\alpha\)-ionol was quantitatively the most abundant norisoprenoid in the studied wines, followed by TDN, \(\beta\)-damascenone and vitispirane. However, among them, only \(\beta\)-damascenone largely exceeded its odor threshold, potentially contributing to wine aroma as an enhancer of fruity aroma [24]. TDN and vitispirane are formed during wine aging, affecting wine with petrol and camphoraceous aroma notes [25]. Prosecco production regulations state that wines from different vintages can be used for refermentation. However, the low concentrations of both TDN and vitispirane and of bicyclic terpen such as 1,8-cineole and 1,4-cineole could indicate that the wines were relatively young wines or that they did not undergo thermal stress during storage [26].