## 3 Results and Discussion  
### Basic Oenological Parameters  
The basic enoological parameters of Malvazija istarska wine produced with _S. cerevisiae_ (SCE) and _S. paradoxus_ (SPA) yeasts are reported in Table 1. In 2021 wines, SPA-21 treatment led to lower ethanol levels compared to the SCE-21 control, while in 2022, the difference was not significant. Several studies reported a reduction in the alcohol content when fermenting with _S. paradoxus_ compared to _S. cerevisiae_, although not always with statistical significance [4; 5; 9; 25]. Glycerol typically ranks second to ethanol in abundance as a yeast metabolite. It often serves as a carbon sink in wines with reduced ethanol content [26]. Evidence suggests that _S. paradoxus_ may divert carbon flux toward glycerol production to a greater extent than _S. cerevisiae_[5], which has been supported by several studies showing increased glycerol levels in _S. paradoxus_-fermented wines [3; 4; 5]. In this study, SPA wines consistently showed higher glycerol levels than SCE wines across both harvest years (Table 1). Glycerol production is regulated by glycerol-3-phosphate dehydrogenases (_GPD_), which are upregulated under osmotic stress during anaerobic fermentation [27]. The observed difference may reflect unique redox balance and osmotic stress adaptations between the two yeasts, consistent with previous findings [4; 28]. The obtained results and previous findings suggest that some of the genes involved in glycerol biosynthesis (_GPD1_, _GPD2_) and transport (_STL1_, _FPS1_) are consistently more expressed in _S. paradoxus_ than in _S. cerevisiae_ under winemaking conditions. The sensitivity of _S. paradoxus_ to grape must fermentation conditions may be linked to its infrequent presence in vineyards, which has limited its exposure to natural selection and adaptation. Indeed, studies have shown that _S. paradoxus_ exhibits lower mutation rates and greater genome stability compared to _S. cerevisiae_ under laboratory evolution conditions [29; 30]. Glycerol contributes positively to the sensory quality of wine, primarily by enhancing its mouthfeel and viscosity, giving it a smoother and fuller texture. Although the sensory effects of glycerol are generally considered subtle and nuanced, the ability of _S. paradoxus_ to produce higher levels can be considered an advantage compared to _S. cerevisiae_. Glycerol production by _S. cerevisiae_ is associated with acetic acid formation, which aids in maintaining redox balance [27; 31]. In 2021, SPA-21 wine exhibited slightly elevated volatile acidity compared to SCE-21 wine, while the difference in 2022 was not significant \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{3}{*}{**Physico-Chemical Parameter**} & \multicolumn{6}{c}{**Differences in Concentration**} \\ \cline{2-7}  & \multicolumn{3}{c}{**One-Way ANOVA**} & \multicolumn{3}{c}{**Two-Way ANOVA**} \\ \cline{2-7}  & \multicolumn{3}{c}{**2021**} & \multicolumn{3}{c}{**2022**} & \multirow{3}{*}{**Y**} & \multirow{3}{*}{**H**} & \multirow{3}{*}{**Y**} & \multirow{3}{*}{**Y**} \\ \cline{2-7}  & **SCE** & & & & & & \\ \hline Alcoholic strength (vol \%) & **13.02**  & 11.45 & 11.57 & n.s. & **21** & * \\ Total acidity (as tartaric acid) & 6.00 & 5.70 & 6.20 & 6.20 & **SCE** & **22** & * \\ Volatile acidity (as acetic acid) & **0.42**  & 0.48 & 0.35 & 0.38 & **SPA** & **21** & n.s. \\ pH & **3.23**  & 3.28  & 0.37  & 0.38 & 3.94 & **SPA** & **22** & n.s. \\ Malic acid & **2.03**  & 1.78  & 1.23  & 0.08 & 0.44 & 0.33 & n.s. & **22** & n.s. \\ Glycerol & **5.33**  & 6.98  & 5.85  & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Standard physico-chemical parameters (g/L, if not otherwise indicated) of Malvazija istarska white wines produced by fermentation with _Saccharomyces cerevisiae_ (SCE) and _Saccharomyces paradoxus_ (SPA) yeasts in two harvest years. (Table 1). Such a result did not entirely align with previous studies that reported lower acetic acid levels in wines fermented with _S. paradoxus_ compared to _S.