## 3 Results and Discussion
Varietal Aroma Compounds in the Plavac Mali Wines Produced by Sequential L, Conventional S and Spontaneous N Fermentation  
The differences between wines produced with three fermentations (L, S, and N) in varietal aromas, terpen, and C13 norisoprenoids were quantitative and qualitative in nature. Wines produced by _Saccharomyces cerevisiae_ had a significantly higher concentration of individual and total terpene compounds, except \(\alpha\)-terpinene, \(\beta\)-myrccene, and _trans_-linalo oxide (furanoid), the maximum of which was in N wines. L wines had the lowest concentration of each individual and total terpene compound, except citronellol acetate only detected in those wines. The type of fermentation had a significant impact on the individual and total sum of C13 norisoprenoids in produced wines. N wines had the highest total sum of norisoprenoids. Wines of three fermentations significantly differed in the concentration of TPB and 2,3-dehydro-4-oxo-\(\beta\)-ionol. The highest concentration of TPB was in N wines and 2,3-dehydro-4-oxo-\(\beta\)-ionol in L wines. N wines differed from S wines in significantly lower concentrations of \(\beta\)-damascenone and higher of 2,5,8-trimethyl-l,2,3,4-tetrahydro-1-naphthalenol. In wines, those varietal aromas exist as glycosidically bound precursors that are released during fermentation by yeast enzyme hydrolyzation [31; 32]. Figure 1: Relative abundance of groups of volatile compounds quantified in wines produced by sequential (_Lachanca thermotolerans_/_S. cerevisiae_), conventional _Saccharomyces cerevisiae_ and spontaneous fermentation. \begin{table}
\begin{tabular}{c c c c} \hline
**Aroma Compound (ug/L)/Yeast** & **L** & **S** & **N** \\ \hline
4-ethyl guaiaicol & nd & 17.67 \(\pm\) 1.41 a & 14.38 \(\pm\) 0.67 b \\
4-ethyl phenol & nd & 96.27 \(\pm\) 2.61 & nd \\ Eugenol & nd & nd & 53.76 \(\pm\) 1.06 \\ \(\Sigma\) Volatile phenols & 0 \(\pm\) 0 & 113.94 \(\pm\) 2.09 a & 68.13 \(\pm\) 1 b \\ \hline Benzaldehyde & 58.03 \(\pm\) 2.23 b & 566.09 \(\pm\) 18.47 a & 42.10 \(\pm\) 1.66 b \\ Benzyl alcohol & 422.79 \(\pm\) 21.06 b & 1610.89 \(\pm\) 147.13 a & 521.31 \(\pm\) 15.57 b \\ Furfuryl alcohol & nd & nd & 150.06 \(\pm\) 10.41 \\ Furfural & nd & 260.99 \(\pm\) 9.82 & nd \\
2,4-dimethyl-3-pentanol & 79.26 \(\pm\) 4.26 b & nd & 112.28 \(\pm\) 8.88 a \\
6-methyl-5-hepten-2-one & 3.21 \(\pm\) 0.07 b & 9.85 \(\pm\) 0.17 a & 11.93 \(\pm\) 1.90 a \\ Acetoin & 14.42 \(\pm\) 1.67 b & nd & 22.24 \(\pm\) 2.49 a \\ Methionol & 53.23 \(\pm\) 3.53 c & 2080.22 \(\pm\) 45.18 b & 5978.68 \(\pm\) 107.43 a \\ \(\Sigma\) Other compounds & 630.95 \(\pm\) 22.45 c & 4528.04 \(\pm\) 162.84 b & 6838.61 \(\pm\) 98.14 a \\ \hline \end{tabular}
\end{table} 
Table 3: _Cont._Yeasts differ in the capability of the detachment of those compounds in dependence on the chemical structure of the sugar and the aglycone moieties [33]. Acid hydrolysis plays an important role in the rearrangements of terpenes and C13 norisoprenoids. Although, a small part of de novo biosynthesized terpene compounds by _Saccharomyces cerevisiae_ have been reported in Cabernet Sauvignon [34; 35]. 2.2 Fermentation Aroma Compounds in the Plavac Mali Wines Produced by Sequential L, Conventional S and Spontaneous N Fermentation  
Among fermentation aromas, L wines had significantly lower concentration of 11 individual (3-methyl-1-butanol, 1-decanol, 1-hexanol, 1-nonanol, 1-octanol, 1-octanol, 1-octanol-3-ol, 1-pentalon, 4-methyl-1-pentanol, 3-penten-1-ol, 2-phenylethanol, _trans_-3-hexen 1-ol) and total sum of higher alcohols. The most abundant higher alcohol in all wines was a 3-methyl-1-butanol (isoamyl alcohol), followed by 1-decanol and 1-hexanol in S and N wines. The 3-methyl-1-butanol and isobutanol have a strong sensory effect on wine [36; 37]. In all wines, the concentration of 3-methyl-1-butanol exceeds its odor detection threshold of 30000 ug/L [38; 39], which provides fresh and jammy fruit and butyric aroma notes [36]. The L wines had the lowest concentration of 3-methyl-1-butanol.