## 3 Results and Discussion  
### The Lactic Acid Bacteria (LAB) Survivability during Cold Storage  
One of the most pivotal factors that affect the quality of fermented beverages is the number of live cells of lactic acid bacteria (LAB) [2]. LAB counts, as well as their survivability during refrigerated storage, are summarized in Table 1. Generally, whey has been reported to be a good medium for the growth of yogurt bacteria [2]. The minimum level of bacteria required for a functional product was reported to be at least 10\({}^{6}\) CFU/mL, and it cannot be lower during storage, until expiration date [2]. After fermentation, the lowest bacterial concentration was noted for sample W (7.65 \(\times\) 10\({}^{6}\)\(\pm\) 1.05 CFU/mL), and the highest LAB counts were observed for samples with FG (2.65 \(\times\) 10\({}^{8}\)\(\pm\) 0.07 CFU/mL and 2.75 \(\times\) 10\({}^{8}\)\(\pm\) 1.63 CFU/mL, for samples WFG1 and WFG2, respectively). There is a lack of reports regarding the effect of the addition of FG to whey on LAB growth. However, the survival rate of LAB in fermented milk with the addition of mucilage and whey-based beverages containing ingredients of plant origin was examined [39; 40]. According to the results described in the literature, LAB were characterized by high survival rates in whey and in whey-based beverages [39; 41]. For instance, [PERSON] et al. [41] found a high survival rate of probiotic bacteria in drinks produced from whey combined with orange, apple and blackcurrant juice. The results of their research, as well as those of other authors, confirm that the addition of plant-based ingredients may create favorable conditions for the growth of LAB [3; 39]. Additionally, [PERSON] and [PERSON] [42] observed high survivability of Lactobacillus counts in symbiotic whey drinks during refrigerated storage for 28 days. [PERSON] et al. [43] showed that soluble dietary fiber from flaxseed functions as a good prebiotic, promoting LAB growth in a kefir model. [PERSON] et al. [44] reported that flaxseed mucilage enhances the starter bacterial counts of stirred yogurt. It can be assumed that, also in our studies, the significantly higher survival of LAB in samples with FG during refrigerated storage (\(p\) < 0.05) compared to W and WMP variants resulted from the presence of FG presumably acting as a prebiotic. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multicolumn{5}{c}{**Time of Storage (Days)**} \\ \cline{2-5}  & **1** & **7** & **14** & **21** & **28** \\ \hline \multicolumn{5}{c}{LAB (CFU/mL)} \\ \hline W & 7.65 \(\times\) 10\({}^{6}\)\(\pm\) 1.05 \({}^{\text{\,\,\,Au}}\) & 5.05 \(\times\) 10\({}^{6}\)\(\pm\) 0.71 \({}^{\text{\,\,\,Au}}\) & 4.86 \(\times\) 10\({}^{6}\)\(\pm\) 0.79 \({}^{\text{\,\,\,Au}}\) & 4.50 \(\times\) 10\({}^{6}\)\(\pm\) 2.15 \({}^{\text{\,\,\,Au}}\) & 4.60 \(\times\) 10\({}^{6}\)\(\pm\) 0.85 \({}^{\text{\,\,\,Au}}\) \\ WMP & 6.40 \(\times\) 10\({}^{6}\)\(\pm\) 1.55 \({}^{\text{\,\,\,Au}}\) & 2.47 \(\times\) 10\({}^{7}\)\(\pm\) 0.20 \({}^{\text{\,\,\,Au}}\) & 5.30 \(\times\) 10\({}^{7}\)\(\pm\) 0.05 \({}^{\text{\,\,\,Au}}\) & 14.90 \(\times\) 10\({}^{7}\)\(\pm\) 0.01 \({}^{\text{\,\,\,Au}}\) & 3.32 \(\times\) 10\({}^{6}\)\(\pm\) 0.05 \({}^{\text{\,\,\,Au}}\) \\ WFG1 & 2.65 \(\times\) 10\({}^{6}\)\(\pm\) 0.07 \({}^{\text{\,\,\,Au}}\) & 7.25 \(\times\) 10\({}^{7}\)\(\pm\) 2.33 \({}^{\text{\,\,\,Au}}\) & 1.15 \(\times\) 10\({}^{6}\)\(\pm\) 0.07 \({}^{\text{\,\,\,Au}}\) & 7.50 \(\times\) 10\({}^{7}\)\(\pm\) 0.71 \({}^{\text{\,\,\,Au}}\) & 1.49 \(\times\) 10\({}^{7}\)\(\pm\) 0.23 \({}^{\text{\,\,\,Au}}\) \\ WFG2 & 2.75 \(\times\) 10\({}^{6}\)\(\pm\) 1.63 \({}^{\text{\,\,\,Au}}\) & 1.15 \(\times\) 10\({}^{6}\)\(\pm\) 0.06 \({}^{\text{\,\,\,Au}}\) & 1.37 \(\times\) 10\({}^{6}\)\(\pm\) 0.14 \({}^{\text{\,\,\,Au}}\) & 4.67 \(\times\) 10\({}^{7}\)\(\pm\) 0.40 \({}^{\text{\,\,\,Au}}\) & 7.90 \(\times\) 10\({}^{7}\)\(\pm\) 0.99 \({}^{\text{\,\,\,Au}}\) \\ \hline \hline \end{tabular}  
\end{table}