# Characterization of Freisa Wines from Piedmont (Italy) by Aroma and Element Profile
## 3 Results and Discussion  
### Volatile Compounds  
A characteristic chromatogram of a Freisa wine sample is reported in Figure 2.  
Unambiguous identification of 46 analytes was performed by NIST library search, provided that the reverse match index was higher than 800. Alternatively, for doubtful cases, injection of pure standards was performed. Wine volatile compounds may be grouped into three different categories, namely: (a) primary aromas, which are already present in the grape or that are formed in pre-fermentation steps; (b) secondary aromas, which are formed by fermentation and other winemaking procedures; and (c) tertiary aromas, which derive from reactions of the previous ones as a consequence of aging. Table 1 reports the volatile compounds identified and listed according to this criterion of grouping. One of the aims of the present paper was to differentiate the five kinds of Freisa according to their VOCs profile; unfortunately, the preliminary survey of the various spectra was not encouraging from this point of view since all the samples showed very similar results. In fact, four analytes were identified as being the most abundant in all the wines analyzed, i.e., isoamyl alcohol, phenylethyl alcohol, ethyl octanoate and diethyl succinate. However, we herein describe the main features of the compounds found in order to characterize Freisa wine as a whole. Among primary aromas, terpen represent the most interesting class of compounds. They are appreciably abundant in aromatic vine varieties but represent a considerable factor contributing to the wine aroma for all the other vines. They usually impart floral or fruity nuances to the wines. Their concentration in wines may vary with aging, because of both hydrolysis reactions of their glycosylated form and of oxidation processes [21; 22]. The most abundant terpenes found in Freisa wines were citronello1 and linalool. Interestingly, traces of limonene, nerolidol and farnesene were detected in a few samples. The overall concentration of terpenes was very similar among the five DOCs, with a slightly higher value for CTF and LF. \begin{table}
\begin{tabular}{l c c c c c c} \hline \multirow{2}{*}{**Compound (\(\mu\)g/L)**} & \multicolumn{2}{c}{**Odor**} & \multicolumn{2}{c}{**Concentration**} & \multirow{2}{*}{} \\  & **Threshold** & & & _OAV_ & \\  & **Value** & & & & \\ \hline  & & **Asti** & **Chieri** & **Colli Tortonesi** & **Langhe** & **Monferato** \\  & & **(FA)** & **(FC)** & **(CTF)** & **(LF)** & **(MF)** \\ \hline \multicolumn{2}{l}{**Varietal Compounds**} & & & & & \\ \hline _Terpenes_ & & & & & & \\ Citronellolol & 100 b & \(1.97\pm 3.16\) & \(3.06\pm 2.11\) & \(3.11\pm 1.00\) & \(3.55\pm 1.20\) & \(3.74\pm 1.80\) \\  & & _0.0197_ & _0.0306_ & _0.0311_ & _0.0355_ & _0.0374_ \\ Limonene & 200 c & \(4.93\pm 6.10\) & \(7.95\pm 11.8\) & \(2.16\pm 3.36\) & \(5.70\pm 7.41\) & \(0.72\pm 2.16\) \\  & & _0.0246_ & _0.0398_ & _0.0108_ & _0.0285_ & _0.0036_ \\ Linalool & 25 c & \(6.84\pm 6.22\) & \(5.20\pm 6.15\) & \(3.93\pm 4.34\) & \(7.92\pm 4.15\) & \(7.67\pm 4.93\) \\  & & _0.274_ & _0.208_ & _0.157_ & _0.317_ & _0.307_ \\ Nerolidol & 0.1 d & \(0.28\pm 0.83\) & \(1.47\pm 2.07\) & \(0.67\pm 1.37\) & \(0.13\pm 0.33\) & \(0.33\pm 0.98\) \\  & & _2.8_ & _14.7_ & _6.7_ & _1.3_ & _3.3_ \\ \(\beta\)-Farnesene & \(0.16\) e & \(0.10\pm 0.42\) & \(0.26\pm 0.85\) & \(0.66\pm 1.62\) & \(0.11\pm 0.41\) & \(0.24\pm 0.72\) \\
**Total** & & _0.625_ & _1.625_ & _4.125_ & _0.688_ & _1.5_ \\
**concentration** & & & & & & \\ _C6 compounds_ & & & & & & \\ \hline
1-hexanol & 8000 c & 0 & \(7.90\pm 15.3\) & \(9.14\pm 8.38\) & \(4.56\pm 8.79\) & \(11.0\pm 22.6\) \\  & & _0.000988_ & _0.00114_ & _0.00057_ & _0.00138_ \\ \hline \end{tabular}
\end{table} 
Table 1: Volatile composition of Freisa wines: odor threshold values (\(\mu\)g/L), concentration (\(\mu\)g/L, mean \(\pm\) standard deviation) and odor activity values a.  
Figure 2: Typical chromatogram (total ion current) obtained from HS-SPME-GC/MS analysis of a Freisa wine.