## 3 Results and Discussion
### Physico-Chemical Parameters of the Worts Produced by Different Mashing Profiles
In their research, the authors found that the colour of non-alcoholic beers is determined by the hop variety as well as its form and quantity. Another important parameter that gives the consumer the first visual impression of the quality of the beer is its turbidity. The formation of haze has a negative effect on the organoleptic properties and clarity of the beer [44]. The beers obtained are characterised by an appropriate level of turbidity, which is also confirmed by research carried out by other scientists [45]. pH is also a key parameter in beer production. During fermentation, various metabolites produced by the yeast--including organic acids--can decrease this quality control parameter [46]. All beers analysed had similar pH values (4.1-4.5), appropriate for a given beer style [47]. The results obtained in terms of ethanol concentration indicate that the yeast used, _Saccharomyces cerevisiae_ var. _chevalieri_, makes it possible to obtain beer with an ethanol content of 0.5% \(v/v\) in the case of the Congress mashing. During the fermentation process, these yeasts used almost none of the available maltose and also assimilated less free nitrogen compounds FAN (Table 4). In turn, after modifying the mashing profile, these yeasts contributed to obtaining beers with an average alcohol content of 0.5-0.8% \(v/v\), using 25% of the available maltose (Table 4). Therefore, in the case of this yeast strain, the mashing process must be modified in the first stage to minimise the production of glucose and produce maltose and dextrins instead. This yeast does not use maltose for fermentation and the resulting beers are rich in dextrins, which is very desirable in the case of NoLo beers [14; 48]. As for beers inoculated with _Saccharomyces cerevisiae_ yeast (US-05), they produced 3.0-3.1% \(v/v\) ethanol in the case of Congress mashing, where there was a higher content of fermentable sugars ( maltose). In this case, the yeast used 100% of the available maltose. After modifying the mashing profile (lower amount of fermentable  
Figure 1: Fermentation kinetics of beers obtained from worn after Congress (**a**) and modified mashing (**b**) with _Saccharomyces cerevisiae_ var. _chevalieri_ and _Saccharomyces cerevisiae_, n = 3; STD < 5%. sugars), the yeast produced an average alcohol content of 2.4-2.7% \(v/v\). This proves that the applied modification of the mashing profile is suitable for traditional yeast strains used in brewing because by reducing the amount of maltose, a significantly lower alcohol content is produced. In the case of maltotriose, it is not surprising that the yeast _Saccharomyces cerevisiae_ used almost the all available sugar in both mash profiles. _Saccharomyces cerevisiae_ var. _chevalieri_ did not use the sugars at all after the Congress mashing. As for the remaining sugars (glucose, fructose, saccharose), both strains had similar sugar content in all variants, and the obtained concentrations of individual sugars did not differ statistically (Table 4). Content of Odour-Active Compounds in Low-Alcohol Beers Produced Using Different Mashing Methods, with or without the Addition of Hops, and with Different Yeast Strains for Fermentation  
The quality of fermented beverages depends largely on the type of yeast strain used in their production, the alcohol concentration and the extract, as well as aroma compounds [49]. Therefore, appropriate modification of the mashing profile or the use of specific yeast strains in the fermentative production of non-alcoholic beers may help preserve the metabolites responsible for their sensory profile [50]. Table 5 shows the content of odour-active compounds found in the beers analysed. During the production of the beers, variants without and with the addition of hops were considered in order to study how the yeast strain used influences the aromatic profile of the obtained beers (_Saccharomyces cerevisiae_ var. _chevalieri_ and _Saccharomyces cerevisiae_ US-05).