# New Isolated Autochthonous Strains of _S. cerevisiae_ for
## 3 Results and Discussion
### Determination of Wine Fermentation By-Products  
Another group of compounds tested were volatile by-products of alcoholic fermentation. These volatiles are derived mainly from yeast metabolism and play important role in shaping the bouquet of the wine. The concentrations of selected by-products determined for white and red wines are shown in Tables 8 and 9, respectively. The tested wines differed statistically (\(p\leq 0.05\)) in terms of the concentrations of analyzed by-products of fermentation. The grapevine variety as well as the yeast strain used affected both the content and the profile of the analytes tested. The dominant group of compounds in studied red and white wines were amyl alcohols. This compounds are secondary yeast metabolites and one of the important aroma compounds in wine. Similar observation have been made by other authors studying Polish wines [1; 94]. However, the obtained concentrations of amyl alcohols in the current study were mostly higher than those reported by [PERSON] et al. [94] for white wines from Seyval blanc (20.4 mg/100 mL) and [PERSON] et al. [1] for red wines from Regent (24.4 mg/100 mL). The differences in the amounts of amyl alcohols between the Polish wines can be attributed to different regions of cultivation of the grapevines used and the winemaking procedure, including the used yeast strains. Regarding the wines studied in this work, red wines (Regent) had a higher content of amyl alcohols (18.684-47.138 mg/100 mL) than the white wines (Seyval blanc) (11.632\(-\)33.204 mg/mL), independent on the yeast strain used. Taking into account the type of yeast strain used, that is, native vs. commercial, most red wines obtained from native strains (NCS) were characterized by a higher content of amyl alcohols than those from commercial strains (CS). The highest amyl alcohol amount for white wine was obtained with the 4_NCS strain, whereas for the red wine group it was with the 8_NCS strain. The lowest amounts were determined in wines fermented with 6_CS and 3_CS in white and red wine, respectively. The reported typical concentration of amyl alcohols in wine ranged from 6.0 to 49.0 mg/100 mL [95]. However, it has been shown that at concentrations up to 30 mg/100 mL they have a positive effect on the aroma and taste of wine (fruity notes), while at higher concentrations (well above 40.0 mg/100 mL) they increasingly dominate the aroma and induce the off-odors by contributing harsh aroma and taste [96]. The other analyzed higher alcohol in wines was iso-butanol. Similar to in the case of amyl alcohols, its concentration was generally higher in red wines (3.965-11.675 mg/100 mL) than in the white wines (2.097-6.037 mg/100 mL). The highest amount of iso-butanol for white wines was determined for 4_NCS, whereas for the red wines for 4_CS. The lowest concentrations was determined in wines fermented with commercial strains 6_CS and 3_CS, in white and red wines respectively. Iso-butanol gives the wine green notes and its acceptable concentration range is from 1.5 to 17.5 mg/100 mL [1; 95; 97]. The concentrations of iso-butanol in all tested white and red wines were within the given concentration range and in the case of white wines, were considerably lower than those reported by [PERSON] et al. [94] (11.05 mg/100 mL).