## 3 Results and Discussion  
### Ethanol pH, Total Acidity, Sugars Content and Color of Must and Wine  
The type of yeast and temperature of fermentation did not significantly affect ethanol production, pH or total acidity (\(p>\) 0.05; Table 1). Ethanol content ranged from 10.8% to 12.2% _v/v_. However, in the case of spontaneous fermentation, ethanol content was lower in the wine fermented at 12 \({}^{\circ}\)C (10.8% _v/v_) than at 20 \({}^{\circ}\)C (11.8% _v/v_). Similar results were reported by [PERSON] et al. (2017) for red wines from grapes, with an alcohol content of 11.9%. According to literature ([PERSON] et al., 2017), key matrix constituents and the relative proportion of water:ethanol in alcoholic beverages as well as their interactions with other matrix components (e.g., sugars, acids, and tannins) can also have significant effects on the behavior of volatile compounds responsible for aroma and flavor. Alcohol content determines the formation of esters and other carbonyl compounds necessary in wine-making. This implies that the concentration of ethanol affects the characteristic quality and flavor of the finished product. Low total acidity and high pH values in our study probably facilitated the yeast metabolism to some extent and were responsible for a relatively high alcoholic strength reached in the wine with dry yeast vs. the control sample ([PERSON] et al., 2017; [PERSON] et al., 2017). The pH of the fresh wine was from 3.0 to 3.1. Maturation further lowered the pH down to 2.8-2.9. The total acidity of the must from cv. Aurore was 11.1 g tartaric acid/L and decreased during the wine-making process. Fresh wines were characterized by acidity ranging from 8.7 g to 10.4 g tartaric acid/L (wines fermented at 12 \({}^{\circ}\)C) and from 8.9 g to 10.7 g tartaric acid/L (at 20 \({}^{\circ}\)C). No significant changes (\(p<\) 0.05) caused by temperature or yeast were perceived. Maturation contributed to a further decline in acidity, and significant differences were observed for different yeast strains (\(p<\) 0.05). The wine fermented without commercial yeast had the lowest acidity at both temperatures (mean 8.5 g tartaric acid/L), and it was the highest in the wine obtained with _S. cerevisiae_ SIHA(r) Cryarone (mean 10.0 g tartaric acid/L). In general, the acidity of wine from cool climate countries is higher. The content of organic acids in the must and wine depends on grape variety, ripeness, climatic conditions during ripening, the grape processing method, conditions of alcohol fermentation and wine storage [20]. Wine acidity is responsible for its sensory characteristics and is important for its preservation. Wines with low pH and a high content of organic acid are less sensitive to microbial spoilage and show more stable coloration [21; 22]. [PERSON] et al. [3] investigated the acidity of wines from southern Poland and found the acidity of wines from cvs. Aurore, Bianca and Jutrzenka to be 3.1, 3.3, and 3.9 g of tartaric acid/L, respectively. [PERSON] et al. [4] examined cool-climate grapevine cultivars from Alden, Bianca, and Aurore and reported their acidity to be 9.8, 9.3, and 7.7 g of malic acid/kg, respectively. In our study, the acidity of Aurore wine was 6.8 g of malic acid/L. During fermentation, 82-96% of the initial amount of sugar was processed into alcohol. The yeasts selected for this study showed a similar pattern of sugar utilization. Moreover, samples that had undergone spontaneous fermentation and with alcohol content at the lowest showed statistically higher residual sugars level (Table 1). No effects of the fermentation temperature were observed (\(p>0.05\)), but the efficiency of sugar processing during fermentation depended on yeast strain (\(p<0.05\)). Additionally, non-_Saccharomyces_ yeasts, especially native ones, disappear because of their weaker ethanol tolerance and inability to survive at its increasing concentration.