# New Isolated Autochthonous Strains of _S. cerevisiae_ for
## 3 Results and Discussion
### Physicochemical Analyses of the Obtained Wines  
Wines differed significantly (\(p\leq\) 0.05) with regard to the content of ethyl alcohol. Obtained results in white wines varied from 12.817 \(\pm\) 0.009% (5_NCS) to 13.307 \(\pm\) 0.004% vol. (6_CS). The ethyl alcohol concentrations in red wines were in the range from 12.093 \(\pm\) 0.029% (8_NCS) to 13.374 \(\pm\) 0.043% vol. (3_CS) (Figure 2). During the fermentation process of white wines, pH changed significantly ([PERSON]'s test) compared to the control sample (grape must, lowest pH). In red wines, the pH was significantly different ([PERSON]'s test) depending on the wine. Significant differences occurred between the average pH values in 2_NCS, 4_NCS, 3_CS wines and grape pulp (lowest pH) and the wine produced with the 4_CS yeast strain (highest pH) (Figure 3). There were no clear trends in total acidity in both white and red wines (Figure 4). The lowest total acidity (4.958 \(\pm\) 0.027 g malic acid/L) was observed in red wine produced with 2_CS yeast strain. Figure 1: Total sugar content in fermented apple juice with non-commercial (NCS) and commercial (CS) _S. cerevisiae_ or non-_Saccharomyces_ yeasts strains. In all wines, volatile acidity increased compared to the raw material, which proves the synthesis of compounds that give the wine a characteristic flavor and aroma bouquet (Figure 5). The main indicators of fruit maturity and proper harvest date are the content of sugar and organic acids, the pH value, and the appropriate characteristics of the peel, stone, and flesh. The _Saccharomyces cerevisiae_ yeast is mainly responsible for the vinicification process. The ethyl alcohol produced by yeast is critical to avoiding the drawbacks of the final product [52]. During the vinicification process, the sugars contained in the raw material are converted into ethanol and carbon dioxide [30]. In this study, the ethanol content was significantly different between produced wines (\(p\leq 0.05\)). All the wines obtained can be classified as medium-strength wines in terms of strength. According to the division of wines in terms of strength, light (weak) wines with a content of up to 10% vol. alcohol, medium-strength, wines 10-14% vol. alcohol; strong wines 14-18% vol. of alcohol; and fortified or alcoholized wines that contain more than 18% vol. alcohol are distinguished [53]. The content of ethyl alcohol affects the taste sensations of the product. It can enhance the  
Figure 3: pH values of white and red wines. Figure 2: Ethanol content of white and red wines. sweetness, change the acidic sensation of wine and increase the intensity of the bitterness while reducing the astringency caused by the presence of tannins (especially with red wines) [54; 55; 56; 57; 58]. Ethanol can also suppress the fruity reading of wines by masking ester perception [54; 59]. As the grapes mature, the relative proportions of the acids change, making it possible to monitor the ripening of the fruit. The sugar content increases slowly, and the acidity decreases markedly [60]. Excessive acidity of wines poses a significant problem in Poland [30; 36]. In the industry, chemical preparations, or selected strains of LAB are used to deacidify wines [30]. Biological de-acidification of wines is carried out by maloalactic fermentation (MLF) [30; 36; 61]. The main sources of acidity in wines are organic acids, naturally contained in grape fruits [21; 62]. The main organic acids found in wines are oxalic, tartaric, formic, malic, acetic, citric, fumaric, succinic, gallic, and lactic. They originate mainly from grapes and are produced as a result of the vinicification process (the metabolism of yeast and other microorganisms, including lactic acid bacteria that conduct maloalactic fermentation) [21; 22]. Organic acids are responsible for the particular sensory features in wines (e.g., they give color and taste and a specific aroma when they form esters in reactions with alcohols). Those features are  
Figure 4: Total acidity of white and red wines. Figure 5: Volatile acidity of white and red wines.