# New Isolated Autochthonous Strains of _S. cerevisiae_ for
## 3 Results and Discussion
### Determination of Wine Fermentation By-Products
The wines with the highest content of amyl alcohols had the lowest amounts of ethyl acetate and vice versa, such as samples 6_NCS, 7_NSC, and 9_NCS. The white wines produced with 6_NCS (isolated from Regent varieties) had the lowest amount of ethyl acetate and one of the highest number of 1-propanol, iso-butanol, and amyl alcohols. Whereas the opposite was obtained for the red wine. The white wines fermented with 7_NSC, and 9_NCS characterized the highest amount of ethyl acetate and the lowest amount of iso-butanol and amyl alcohols. In the case of the 9_NCS strain, a similar correlation was also found in red wines. Our findings are in agreement with the observations previously reported for Polish wines by [PERSON] et al. [1]. The acetaldehyde content in white wines ranged from 3.005 to 4.689 mg/100 mL, except for 6_NCS (5.853 mg/100 mL) and 6_CS (7.267 mg/100 mL). Its concentration in red wines was more varied and ranged from 1.557 to 17.05 mg/100 mL. Acetaldehyde is the dominant carbonyl compound in wine. It imparts the flavor of the wine by aroma descriptors such as \"bruised apple\" and \"nutty\". In the case of white wines, it can indicate oxidation of the wine, while in red wines, it takes a part in stabilizing wines during aging (it is involved in the polymerization reactions of anthocyanins and phenols). Moreover, at concentrations below 10.0 mg/100 mL, it can contribute to the complexity of the aroma of red wines. A typical range of acetaldehyde concentrations in the wine is from 1.0 to 7.5 mg/100 mL [95]. In our study, white wines and most red wines fell within the above-mentioned concentration range. Only four red wines fermented with 3_NCS, 6_NCS, 1_CS,and 5_CS had considerably higher amounts of acetaldehyde. The high amount of this compound in these wines can be related to the specific metabolic activity of these yeast strains. The strain 6_NCS, as mentioned above, had the highest amount of ethyl acetate, methanol, 1-propanol, and one of the highest amounts of iso-butanol among the tested red wines fermented with native strains. Thus, the obtained results confirm the findings of other authors that acetaldehyde concentration is yeast strain-dependent [95]. The analysis of the obtained results showed a large diversity of the native _S. cerevisiae_ strains used in terms of the amount of synthesized volatiles. The highest amount of amyl alcohols, iso-butanol, 1-propanol, and ethyl acetate showed white wines fermented with strain 4_NCS (isolated from Regent). The determined concentrations, except 1-propanol, were within the ranges typical for wines. The strains 4_NCS were among the other, that is, 5_NCS, 6_NCS, and 7_NCS _S. cerevisiae_ isolated from the Regent grape variety. Despite the fact that they were isolated from similar grape species, they differed in terms of the amount of synthesized compounds, which clearly indicates their biodiversity. A similar observation was made on the _S. cerevisiae_ isolated from Solaris, that is, strain 1_NCS, 2_NCS, 3_NCS, 9_NCS. Interestingly, white wines fermented with the 8_NCS isolated from Seyval blanc grapevines growing in a region other than that used for fermentation were characterized by intermediate values of the analyzed by-products. Whereas the red wine produced with the 8_NCS showed the highest amount of amyl alcohols and one of the highest amounts of iso-butanol. However, in the case of amyl alcohols, their concentration was 47.138 mg/100 mL, above the value recognized as the limit of the positive impact on the aroma of the wine.