## 3 Results and Discussion
### Physico-Chemical Parameters of the Worts Produced by Different Mashing Profiles
In the beers analysed, 28 odour-active aroma compounds were detected, including 8 alcohols, 9 esters, 8 terpenes and 3 compounds classified as other. The detected aromas were divided into six odour groups: roasted (R), fruity (FR), floral (FL), herbaceous (H), chemical (C) and animal (A). The first group analysed was the higher alcohols, which affect the taste of beer by increasing the perception of alcohol and giving a warmer sensation in the mouth. The process of biosynthesis of these compounds requires the involvement of several genes and is directly related to the metabolism of amino acids via the Ehrlich pathway [51; 52]. Among the alcohols analysed, the highest concentrations were found in compounds such as 2-methyl-1-propanol, which gives the beer a mild and sweet aroma [53]. The highest amounts of this compound were produced during fermentation with the yeast _Saccharomyces cerevisiae_ US-05, regardless of the mashing profile used. In the case of 2-methyl-1-butanol (malt and sweet aroma), beers fermented with _Saccharomyces cerevisiae_ also contained higher concentrations of this compound after modification of the mashing profile. With respect to the Congress mashing, beers without the addition of hops after fermentation with _Saccharomyces cerevisiae_ var. _chevalieri_ were characterised by a higher value of 2-methyl-1-propanol. The concentration of this compound in all the samples analysed was above the detection limit, which is also confirmed by the analyses of the intensity of the individual aromas presented in Table 6. Higher alcohols such as 1-hexanol also impart herbal and green aromas to the beer. This compound was present above the detection limit in the beers analysed and the highest concentration was observed in beers fermented with the yeast strain _Saccharomyces cerevisiae_. 2-Phenylethanol was also found above the detection limit in all analysed samples. A significantly higher concentration of this compound was observed in beers mashed according to the Congress method without the addition of hops, both after fermentation with _Saccharomyces cerevisiae_ var. _chevalieri_ and _Saccharomyces cerevisiae_. The aromatic alcohol 2-phenylethylhanol has a sweet rose aroma and has a positive effect on the aroma of beer. This compound is also thought to mask the perception of dimethyl sulphide (DMS) [54]. The higher alcohols analysed in this paper contributed significantly to the final aroma of the beers obtained, as confirmed by the results of the olfactometric analysis. Both the strain used for the production of non-alcoholic beers (_Saccharomyces cerevisiae_ var. _chevalieri_ as well as _Saccharomyces cerevisiae_ strain) after modification of the mashing profile, contributed to the production of a significantly higher content of these compounds compared to low-alcoholic and non-alcoholic beers produced by other methods [55; 56]. Of the nine esters analysed, seven had a concentration above the detection limit (Table 5). The dominant aromas belonged to the group of fruity and floral compounds. Esters are formed intracellularly as a result of the fermentation of yeast cells [57]. One of the most important esters with flavour and aroma effects in beer is ethyl acetate, which gives beer a floral and solvent aroma [58], which was also confirmed by olfactometric analysis. The highest concentration of ethyl acetate was found in beer without the addition of hops fermented with the yeast _Saccharomyces cerevisiae_ var. _chevalieri_, compared to other variants (Table 5). The values obtained are higher than in the studies carried out by [PERSON] et al. [56]. Ethyl propionate also had a significant effect on the flavour of the beers obtained. This compound is characterised by a pineapple aroma. The highest concentration of this compound was found in beers after modified mashing fermented with the yeast strain _Saccharomyces cerevisiae_. In the case of ethyl hexanoate, the highest concentration of this compound occurred in beers with hops in both mashing profiles (Table 5).