# Characterization of Freisa Wines from Piedmont (Italy) by Aroma and Element Profile
## 3 Results and Discussion
### Volatile Compounds
\begin{table}
\begin{tabular}{l c c c c c c} \hline \hline \multirow{2}{*}{**Compound (ug/L)**} & \multicolumn{2}{c}{**Odor**} & \multicolumn{3}{c}{**Concentration**} & \\  & \multicolumn{2}{c}{**Threshold**} & \multicolumn{3}{c}{**OAV**} & \\  & \multicolumn{2}{c}{**Value**} & & \multicolumn{2}{c}{**OAV**} & \\ \hline _C13-norisopenroids_ & & & & & & \\ \(\alpha\)-Ionone & 0.09 \({}^{\text{c}}\) & 33.5 \(\pm\) 36.2 & 25.4 \(\pm\) 37.9 & 17.8 \(\pm\) 14.3 & 19.7 \(\pm\) 8.61 & 16.6 \(\pm\) 12.3 \\ _Lactones_ & & & & & & \\ Butyrolactone & 1000 \({}^{\text{k}}\) & 0.22 \(\pm\) 0.44 & 0.52 \(\pm\) 1.33 & 0.30 \(\pm\) 0.48 & 0.035 \(\pm\) 0.13 & 0.028 \(\pm\) 0.083 \\  & & _0.00022_ & _0.00052_ & _0.0003_ & _0.000035_ & _0.000028_ \\ OAV range & & 0.0000148–62.6 & _0.000025_–80 & _0.000025_–58.4 & _0.0000095_–44 & _0.000028_–62 \\ \hline \hline \end{tabular}  
* Calculated as the ratio concentration/odor threshold value. \({}^{\text{b}}\) Retrieved from Ref [11]. \({}^{\text{k}}\) Retrieved from Ref [12]. \({}^{\text{d}}\) Retrieved from Ref [13]. \({}^{\text{e}}\) Retrieved from Ref [14]. \({}^{\text{f}}\) Retrieved from Ref [15]. \({}^{\text{g}}\) Retrieved from Ref [16]. \({}^{\text{h}}\) Retrieved from Ref [17]. \({}^{\text{l}}\) Retrieved from Ref [18]. \({}^{\text{l}}\) Retrieved from Ref [16]. \({}^{\text{h}}\) Retrieved from Ref [17]. \({}^{\text{l}}\) Retrieved from Ref [18]. \({}^{\text{l}}\) Retrieved from Ref [19] \({}^{\text{k}}\) Retrieved from Ref [20]. \({}^{\text{N/A}}\) = not available. OAV are reported in Italics. Organic compounds classes and their total concentrations are reported in bold.  
\end{table} 
Table 1: _Cont._benzaldehyde and benzeneacetaldehyde. Overall concentrations ranged from 0.70 \(\upmu\)g/L for LF to 3.0 \(\upmu\)g/L for CT.  
Fatty acids feature unpleasant scents of rancidity. Therefore, their presence in wines is not recommended. They usually undergo esterification reactions with the alcohols present in wine, and hence their concentration is limited by this occurrence. The most abundant was decanoic acid; however, its concentration was largely below the odor threshold of 1000 \(\upmu\)g/L, as reported by some authors [25]. Total fatty acids concentration goes from 46 \(\upmu\)g/L for CT to 120 for FA. Volatile phenols found in Freisa wines were 4-ethylphenol and 4-ethyl-2-methoxy-phenol (4-ethyl guaiacol). This class of compounds is yielded by the de-carboxylation of hydroxycinnamic acids present in must by some microorganisms (Brettanomyces yeasts and bacteria) [23; 31]. Since these microorganisms are wine contaminants, the above-mentioned phenols represent defects of wines, mainly because of their unpleasant smell. The odor threshold reported in the literature for 4-ethyl guaiacol is 33 \(\upmu\)g/L [19] and 440 \(\upmu\)g/L for 4-ethyl phenol [12]. Among the wines studied, the concentration values for 4-ethyl phenol were always lower than the threshold; on the other hand, for 4-ethyl guaiacol, only CT wines reached a value comparable to the threshold (34.4 \(\upmu\)g/L); this value corresponds to an odor activity value (OAV), calculated as the ratio between the concentration and the odor threshold, of about one, which may be considered negligible [20]. Freisa wines are usually consumed within a few years after bottling. Hence, the concentration of tertiary aromas was expected to be low, as indeed was found. However, it is remarkable that we found a substance belonging to the class of norisoprenoids. This is a valuable occurrence since norisoprenoids, which are formed by the degradation of carotenoids [32], impart positive notes to the wine. The compound was \(\alpha\)-ionone (cedarwood scent), with concentrations ranging from 16.6 for MF to 33.5 \(\upmu\)g/L for FA. Moreover, aging determines the passage from wood to the wine of many types of interesting substances, such as lactones. Here, \(\gamma\)-butyrolactone was detected in all the DOCs studied; however, its concentration is very low and reaches the maximum value for CT wines (0.52 \(\upmu\)g/L).