# Impact of Selected Yeast Strains on Quality Parameters of Obtained Sauerkraut
## 3 Results and Discussion
### Organic Acids and Sugars
Decreasing the concentration of acetic acid may be advantageous for sauerkraut, as this component imparts a sharp vinegary aroma to the product even in small amounts. A small amount of acetic acid is acceptable; in fact, high-quality sauerkraut typically maintains an acetic acid to lactic acid ratio of 1:4 and lower [16]. The quantity of other analysed organic acids varied slightly among the samples (Table 2). These acids originate primarily from the raw material and cabbage, and their levels typically decrease during fermentation, as they are used as a carbon source by yeast [17]. White cabbage contains 110-220 mg per g of the DW (dry weight) of fermentatable sugars, mainly glucose and fructose [18]. During fermentation, microorganisms gradually use sugars for their growth and cellular metabolism [19]. The increased availability of sugars in the fermentation environment may have contributed to the production of higher concentrations of lactic acid. Fructose and glucose were the main sugars that remained in the fermented material (Table 2). The samples contained from 0.84 to 6.70 g/kg of glucose and from 2.22 to 4.67 g/kg of fructose. \begin{table}
\begin{tabular}{l||c c|c|c|c|c|c|c|c|c|c|c|c} \hline \hline  & \multicolumn{1}{c}{**(g/kg)**} & \multicolumn{1}{c}{**(Fructose, mainly present in a free, soluble form, is rapidly metabolised by microorganisms. One of the metabolic byproducts of fructose metabolism is mannitol [20]. Mannitol is primarily produced by lactic acid bacteria, mainly of the _Leuconostoc_ genus [21]. Yeast can utilise this component as a carbon source [22]. This phenomenon is particularly noticeable in samples fermented with yeasts of the _P. fermentatus_ Pf9 and _Rh. mucilaginousa_ Rm26 strains, where the lowest amounts of mannitol were found. Both microorganisms have previously been implicated in the assimilation of acetic and lactic acid. Glycerol formation is typically associated with the presence of fungal microorganisms, such as _Saccharomyces_ and non-_Saccharomyces_ yeast [23]. However, no significantly higher concentrations of glycerol were observed in the samples containing yeast compared with the control sample. This observation may support previous suggestions regarding the production of glycerol by prokaryotes [24]. The lowest concentration of glycerol was found in sauerkraut fermented with _Pichia fermentatus_ Pf9, suggesting the possible utilisation of this component as a carbon source. The obtained sauerkraut contained between 2 and 6 g/kg of ethanol. Similar amounts of this compound have been reported in a study by [PERSON] et al. [25]. In most samples, we observed higher concentrations of ethanol after the addition of yeast to the fermentation than in that in the control sample. This underlines the important role of these microorganisms in introducing ethanol into the food matrix. However, two samples fermented with _Rh. mucilaginousa_ Rm26 and _P. fermentatus_ Pf9 showed a reduction in ethanol content compared with the control. Yeast utilise the ethanol degradation pathway to redirect carbon flow towards the synthesis of acetyl-CoA. As a result, different types of ethyl esters of various acids are generated as by-products of this transformation process [26].