## 3 Results and Discussion
### Volatile Compounds
#### 3.4.1 Terpenoids  
Grape-derived terpenoids are key contributors to the distinct and characteristic aromas typical for a cultivar. This effect is especially pronounced in wines with higher terpenoid levels, such as those made from muscats and other aromatic grape cultivars [40,41]. However, it also extends to cultivars which are less aromatic but have a notable monoterpenol potential, like Malvazija istarska [15]. Monoterpenols, like linalool, geraniol, citronellol, nerol, and ho-trienol, are the most impactful for wine aroma among terpenoids, adding appealing floral and fruity notes. In addition to enzymes originating from grapes, yeast \(\beta\)-glucosidase and other enzymes can also affect their content and composition during fermentation. This can occur through yeast-specific cleavage of glycosidic bonds to release volatile terpenoid aglycons or through various other transformations and interconversions [42, 43, 44]. In most cases in which significant differences were observed, SCE wines had higher concentrations of terpenoids in a single or in both harvest years (Table 4). According to one-way ANOVA, the concentrations of limone, \(\alpha\)-terpinolene, an unidentified monoterpene (LRI 1456), _trans_-furan linalool oxide, neryl ethyl ether, \(p\)-menth-1-en-9-al, and citronellyl acetate were higher in SCE-21 than in SPA-21 wine, while _trans_-\(\beta\)-ocimene was more abundant in SCE-22 than in SPA-22 wine. Epoxyternipolene, _trans_-2-pinanol, and neryl acetate had higher concentrations in SCE wines from both years. In addition, two-way ANOVA showed significant differences in favour of SCE wines for \(\alpha\)-ocimene, \(\gamma\)-terpinene, and \(\alpha\)-curcumene. Isomenthone and _cis_,_trans_-farnesol, on the other hand, showed a tendency to higher concentration in SPA wines. The higher levels of specific terpenoids observed in SCE compared to SPA wines in this study suggest that _S. cerevisiae_ exhibits greater \(\beta\)-glucosidase native activity than _S. paradoxus_. However, the major monoterpenols remained unaffected, while most of the influenced terpenoids were specific derivatives, such as acetates, ethers, and oxides. This indicated that these differences might have stemmed from other terpenoid transformations and interconversions induced by yeast during fermentation, rather than solely from the cleavage of glycosides. As the contribution of the affected terpenoids to wine aroma remains mostly unknown, it is unclear whether the observed differences influence the expression of varietal aroma in the two wines studied. Several terpenoids showed significant variability based on harvest year, with higher concentrations in 2021 wines than in those from 2022. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline  & & & & & & \multicolumn{6}{c}{**Differences in Concentration**} \\ \cline{4-11}
**Co.** & **Volatile Compounds** & **ID** & **LRI\({}_{\text{e}}\)** & **LRI\({}_{\text{1}}\)** & \multicolumn{6}{c}{**One-Way ANOVA**} & \multicolumn{6}{c}{**Two-Way ANOVA**} \\ \cline{4-11} \cline{4-11}  & & & & & **2021** & & **2022** & & \\ \cline{4-11}  & & & & & & **SCE** & **SPA** & **SCE** & **SPA** & **H** & \(\mathbf{Y}\times\mathbf{H}\) \\ \hline TE1 & \(\beta\)-Pinene & B & 1141 & - & 1.40 & 0.25 & 2.96 & 3.42 & n.s. & **22** & n.s. \\ TE2 & \(\beta\)-Mycrene & A, B, C & 1160 & 1159 & 10.50 & 6.97 & 8.72 & 10.25 & n.s. & n.s. & n.s. \\ TE3 & \(\alpha\)-Phellandrene & B, C & 1174 & 1172 & 0.30 & 0.14 & 0.41 & 0.36 & n.s. & n.s. & n.s. \\ TE4 & \(\beta\)-Phellandrene & B, C & 1190 & 1186 & n.d. & n.d. & 4.94 & 4.60 & - & - & - \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Concentrations (\(\mu\)g/L) of terpenoids found in Malvazija istarska white wines produced by fermentation with _Saccharomyces cerevisiae_ (SCE) and _Saccharomyces paradoxus_ (SPA) yeasts in two harvest years determined by untargeted two-dimensional gas chromatography with time-of-flight mass spectrometry (GC \(\times\) GC/TOF-MS).