## 3 Results and Discussion
### Bound Volatile Aroma Compounds in Fresh Grapes and Dried Grapes  
Concentrations of volatile aroma compounds identified and quantified after acid hydrolysis are presented in the Supplementary Material (Table S1). The concentration of terpene compounds in the fresh grape juice was higher in the bound than free forms. This was quite remarkable considering that terpene compounds are responsible for floral and citrus aromas of wines. In particular, the highest amount was revealed for linalool oxide (5.43 \(\mu\)g/L) and linalool (4.01 \(\mu\)g/L). Linalool represented almost 42% of all terpenes found in bound fraction. Other authors [11] have reported 19% of monoterpene alcohol linalool in the bound form of 'Fiano' grapes. We identified 15 glycosidically bound compounds consisting of three alcohols (1-butanol, 2-hexen-1-ol, and 1-hexanol), six terpen (myrcene, o-cymene, linalool oxide, linalool, terpinen-4-ol, and linalool acetate), two aldehydes (2-hexenal and benzaldehyde), two ketones (6-methyl-5-heptene-2-one and 2,3-pentadone), and \(\beta\)-damascenone in greenhouse-dried grapes as presented in Table 3. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Compound**} & \multirow{2}{*}{**Abbreviation**} & \multicolumn{4}{c}{**Concentration (\(\mu\)g/L)**} \\ \cline{3-5}  & & **Fresh Grapes** & **G-D Grapes** & **C-D Grapes** \\ \hline
1-butanol & A2 & 0.02  & 0.80  & 0.12  \\
2-hexen-1-ol & A5 & n.d. & 15.50  & n.d. \\
1-hexanol & A6 & n.d. & 60.75  & n.d. \\ \(\Sigma\)Alcohols & Alcohols & & & \\ \hline ethyl acetate & E1 & n.d. & 0.91  & 7.87  \\ \(\Sigma\) Esters & Esters & & & & \\ \hline \(\alpha\)-pinene & T1 & n.d. & n.d. & 0.11  \\ myrcene & T2 & 0.43  & 1.08  & 1.46  \\ o-cymene & T3 & 0.55  & 2.16  & 1.74  \\ linalool oxide & T4 & 5.43  & 14.56  & 49.90  \\ linalool & T5 & 4.01  & 17.11  & 16.99  \\ terpinen-4-ol & T8 & 0.06  & 1.99  & 0.82  \\ linalool acetate & T12 & 0.01  & 0.19  & n.d. \\ \(\Sigma\) Terpenes & Terpenes & & & \\ \hline
2-hexenal & Ald-1 & 0.31  & 2.24  & 0.21  \\ benzaldehyde & Ald-2 & 0.72  & 2.30  & 1.90  \\ \(\Sigma\) Aldehydes & Aldehydes & & & \\ \hline
6-methyl-5-heptene-2-one & K2 & n.d. & 0.16  & 0.23  \\
2,3-pentadiene & K3 & 0.07  & 0.50  & n.d. \\ \(\Sigma\) Ketones & Ketones & & & \\ \hline \(\beta\)-damascenone & \(\beta\)-dem & 15.58  & 67.78  & 11.89  \\ \hline \(\Sigma\) benzenoids & Benzenoids & 0.51  & 2.19  & 1.20  \\ (A7 + A8 + Ald-2) & & & & \\ \hline \hline \end{tabular}  
* Different letters within the row (a, b, c)—indicate significant differences, \(p<0.05\). n.d. not detected  
\end{table} 
Table 3: Bound fraction of volatile aroma compounds in fresh grapes, greenhouse-dried (G-D) grapes, and chamber-dried (C-D) grapes at 50  & 7.87  \\ \(\Sigma\) Esters & Esters & & & \\ \hline \(\alpha\)-pinene & T1 & n.d. & n.d. & 0.11  \\ myrcene & T2 & 0.43  & 1.08  & 1.46  \\ o-cymene & T3 & 0.55  & 2.16  & 1.74  \\ linalool oxide & T4 & 5.43  & 14.56  & 49.90  \\ linalool & T5 & 4.01  & 17.11  & 16.99  \\ terpinen-4-ol & T8 & 0.06  & 1.99  & 0.82  \\ linalool acetate & T12 & 0.01  & 0.19  & n.d. \\ \(\Sigma\) Terpenes & Terpenes & & & \\ \hline
2-hexenal & Ald-1 & 0.31  & 2.24  & 0.21  \\ benzaldehyde & Ald-2 & 0.72  & 2.30  & 1.90  \\ \(\Sigma\) Aldehydes & Aldehydes & & & & \\ \hline
6-methyl-5-heptene-2-one & K2 & n.d. & 0.16  & 0.23 [Bound forms of 2-hexen-1-ol, 1-hexanol, and linalool acetate 2,3-pentadione were not found in chamber-dried grapes. Citronellol, nerol, and geraniol were not found in bound forms in fresh nor in dried grapes regardless of the dehydration technique. Early work of [PERSON] et al. [37] demonstrated that these three monoterenes never exceeded the glycosidically bound concentration of \(\alpha\)-terpineol in juice, which was similar to our results because \(\alpha\)-terpineol was also not found in bound forms in any types of juices. Compared to terpen, the concentration of bound \(\beta\)-damascenone was affected most by the dehydration method, with an increasing concentration in greenhouse-dried grapes.