## 3 Results and Discussion
### Free Volatile Aroma Compounds in Fresh and Dehydrated Grapes
\begin{table}
\begin{tabular}{c c c c c c} \hline \multirow{2}{*}{**Compound**} & \multirow{2}{*}{**Abbreviation**} & \multicolumn{4}{c}{**Concentration (ug/L)**} & \multirow{2}{*}{\(p\)**-Value**} \\ \cline{3-3} \cline{5-6}  & & **Fresh Grapes** & & **G-D Grapes** & & **C-D Grapes** \\ \hline geranid & T13 & 0.29 \(\pm\) 0.17 \({}^{\rm a}\) & 0.4 \(\pm\) 0.05 \({}^{\rm a}\) & 0.10 \(\pm\) 0.01 \({}^{\rm a}\) & \textless{}0.05 \\ geranyl acetone & T14 & 0.08 \(\pm\) 0.03 \({}^{\rm a}\) & 0.03 \(\pm\) 0.20 \({}^{\rm b}\) & 0.04 \(\pm\) 0.01 \({}^{\rm a}\) & 0.539 \\ meridold & T15 & 0.8 \(\pm\) 0.1 & n.d. & n.d. & - \\ \(\Sigma\) terpen & Terpenes & 11.23 \(\pm\) 4.14 \({}^{\rm a}\) & 19.06 \(\pm\) 0.98 \({}^{\rm a}\) & 19.4 \(\pm\) 3.1 \({}^{\rm a}\) & 0.859 \\ \hline
2-hexanaldehyde & Ald-1 & 5.19 \(\pm\) 1.15 \({}^{\rm a}\) & 5.61 \(\pm\) 0.4 \({}^{\rm a}\) & 0.18 \(\pm\) 0.03 \({}^{\rm b}\) & \textless{}0.05 \\ benzaldehyde & Ald-2 & 1.49 \(\pm\) 0.48 \({}^{\rm a}\) & 4.51 \(\pm\) 0.31 \({}^{\rm b}\) & 13.11 \(\pm\) 8.03 \({}^{\rm b}\) & 0.129 \\ acetal & Ald-3 & 0 \(\pm\) 0.04 \({}^{\rm a}\) & 0.07 \(\pm\) 0 \({}^{\rm b}\) & 0.4 \(\pm\) 0.46 \({}^{\rm a}\) & 0.265 \\ \(\Sigma\) aldehydes & Aldehydes & 6.68 \(\pm\) 1.32 \({}^{\rm a}\) & 9.99 \(\pm\) 0.44 \({}^{\rm b}\) & 13.7 \(\pm\) 8.52 \({}^{\rm a}\) & 0.471 \\ \hline \(\alpha\)-ionone & K1 & n.d. & n.d. & n.d. & - \\
6-methyl-5-heptene & K2 & 1.14 \(\pm\) 0.24 \({}^{\rm a}\) & 0.79 \(\pm\) 0.01 \({}^{\rm a}\) & 1.24 \(\pm\) 0.58 \({}^{\rm a}\) & 0.239 \\ \(\Sigma\) & Terpenations & K3 & 0.52 \(\pm\) 0.1 \({}^{\rm a}\) & 2.29 \(\pm\) 0.09 \({}^{\rm b}\) & 3.37 \(\pm\) 3.85 \({}^{\rm a}\) & 0.633 \\ \(\Sigma\) ketones & Ketones & 1.66 \(\pm\) 0.18 \({}^{\rm a}\) & 3.08 \(\pm\) 0.1 \({}^{\rm b}\) & 4.61 \(\pm\) 4.43 \({}^{\rm a}\) & 0.561 \\ \hline \(\beta\)-damascenone & \(\beta\)-dem & 4.01 \(\pm\) 1.7 \({}^{\rm a}\) & 1.44 \(\pm\) 0.27 \({}^{\rm b}\) & 0.35 \(\pm\) 0.19 \({}^{\rm b}\) & \textless{}0.05 \\ \hline \(\gamma\)-hexalactone & \(\gamma\)-hex & 0.13 \(\pm\) 0.03 \({}^{\rm a}\) & 0.08 \(\pm\) 0.02 \({}^{\rm a}\) & 0.25 \(\pm\) 0.02 \({}^{\rm b}\) & \textless{}0.05 \\ \hline \(\Sigma\) benzenoids & Benzenoids & 1.69 \(\pm\) 0.46 \({}^{\rm a}\) & 4.43 \(\pm\) 0.32 \({}^{\rm b}\) & 13.81 \(\pm\) 8.22 \({}^{\rm b}\) & 0.119 \\ \hline \end{tabular} Different letters within the row (a, b)—indicate significant differences, \(p<0.05\) n.d. not detected.  
\end{table} 
Table 2: _Cont._The composition of free volatile compounds found in 'Marastina' grapes was typical for the non-aromatic grapes. The concentrations of free alcohols and terpen were similar to 'Fiano' grape juice used for the production of dry wine Fiano di Avellino, as well as for the sweet wines [11]. Interestingly, a relatively high concentration of \(\beta\)-damascenone was also detected in the free volatile fraction in 'Marastina' grapes. It is already known that the free form of aroma compounds occur in the non-aromatic grapes in concentrations lower than their sensory threshold. However, several studies have shown a positive correlation between the sensory characteristics of the pool of volatile compounds released from grape glycosylated precursors and the varietal sensory properties of the wines obtained from them [11; 12; 23]. Dehydration technique significantly impacted the concentration of free volatile compounds found in the dried grapes of 'Marastina'. Significant differences were found for 18 out of 35 volatile compounds. There was a general increasing trend for the concentration of the free volatile compounds of 'Marastina' grapes subjected to dehydration. An increase in concentration of free volatile compounds is expected as a result of water loss by evaporation during partial drying. This is in agreement with the results of [PERSON] et al. on the 'Perdo Ximenez' must of sun-dried grapes. Dehydration increased the concentration of total alcohols in greenhouse-dried grapes. The ratios among individual alcohols in dried grapes followed a similar trend to those in fresh grapes.