## 3 Results and Discussion
### Microbiological Quality and Biological Activity of Fermented OBB
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Oat Beverages**} & \multicolumn{2}{c}{**Chokeberry Extract**} & \multicolumn{2}{c}{**Chokeberry lyophilistate**} \\ \cline{2-5}  & **0 h** & **20 h** & **0 h** & **20 h** \\ \hline \hline \multicolumn{5}{c}{TPC (mg GAE/L)} \\ \hline Control & 84.93 \({}^{\text{BB}}\)\(\pm\) 1.89 & 64.92 \({}^{\text{AA}}\)\(\pm\) 3.50 & 84.93 \({}^{\text{BB}}\)\(\pm\) 1.89 & 64.92 \({}^{\text{AA}}\)\(\pm\) 3.50 \\
1\% addition & 216.97 \({}^{\text{CC}}\)\(\pm\) 11.85 & 208.53 \({}^{\text{GC}}\)\(\pm\) 5.58 & 205.76 \({}^{\text{CC}}\)\(\pm\) 2.51 & 201.29 \({}^{\text{CC}}\)\(\pm\) 5.83 \\
5\% addition & 215.69 \({}^{\text{CC}}\)\(\pm\) 9.99 & 201.86 \({}^{\text{CC}}\)\(\pm\) 9.05 & 242.94 \({}^{\text{ID}}\)\(\pm\) 9.18 & 213.71 \({}^{\text{CC}}\)\(\pm\) 8.31 \\ \hline \hline \multicolumn{5}{c}{Antioxidant activity (mM Trolox/L)} \\ \hline Control & 0.657 \({}^{\text{BB}}\)\(\pm\) 0.034 & 0.603 \({}^{\text{BB}}\)\(\pm\) 0.033 & 0.657 \({}^{\text{AB}}\)\(\pm\) 0.034 & 0.603 \({}^{\text{BB}}\)\(\pm\) 0.033 \\
1\% addition & 0.648 \({}^{\text{BB}}\)\(\pm\) 0.005 & 0.517 \({}^{\text{AA}}\)\(\pm\) 0.017 & 0.750 \({}^{\text{BC}}\)\(\pm\) 0.021 & 0.627 \({}^{\text{AB}}\)\(\pm\) 0.021 \\
5\% addition & 0.792 \({}^{\text{CD}}\)\(\pm\) 0.007 & 0.489 \({}^{\text{AA}}\)\(\pm\) 0.011 & 0.847 \({}^{\text{CD}}\)\(\pm\) 0.022 & 0.638 \({}^{\text{AB}}\)\(\pm\) 0.056 \\ \hline \hline \end{tabular}  
* Averages with different small letters (*) are significantly different at \(p<0.05\) (comparison within a group of samples with the addition of extract and lyophilistate separately). Averages with different capital letters (*D) are significantly different at \(p<0.05\) (comparison between groups of samples with the addition of extract and lyophilistate).  
\end{table} 
Table 4: The effect of chokeberry extracts and lyophilistate addition on total polyphenol content and antioxidant activity of fermented oat beverages. decreasing the total polyphenol content and antioxidant activity were observed during the fermentation of blueberry juices [77] and beetroot and carrot juices with LAB [78] or vegetable and fruit beverages with _L. plantarum_[77]. For example, [PERSON] et al. [76] observed a decrease in TPC value after the fermentation of curly kale juice, indicating changes in the amount of some phenolic compounds including sinapic acid, quercetin, or kaempfer. These changes may result from the activity of phenolic compounds acting as reducing agents, singlet oxygen quenchers, or hydrogen donors, causing fluctuations in the TPC and antioxidant capacity [78]. The decrease in phenolic content is most often explained by the bioconversion of phenolic compounds and the rearrangement of their structure due to the acidic environment resulting from the fermentation process. The self-polymerisation or interaction with other compounds such as amino acids is also proposed [79; 80; 81]. The prepared oat beverages, both without and with the addition of chokeberry extracts and lyophilates, were characterised by good microbiological quality. _E. coli, Enterobacteriaceae_ rods, as well as fungi including yeast and filamentous fungi were not detected in any of the beverages. Therefore, it could be stated that the obtained product does not pose a threat to consumers' health. In turn, the number of LAB was around 10\({}^{7}\)-10\({}^{8}\) CFU/mL after inoculating the drinks with starter cultures and increased significantly after 20 h of fermentation in all variants (Figure 5). Due to the high number of the selected LAB strains, the obtained product may be considered potentially probiotic. After the fermentation process in oat beverages with the addition of chokeberry extract or lyophilate, the number of LAB was comparable (in the case of the lyophilate and a 1% extract addition) or significantly higher (for a 5% extract addition) compared to the control sample.