# Changes in Selected Quality Indices in Microbially Fermented Commercial Almond and Oat Drinks
## 3 Results and Discussion
### Aidity Changes after the Fermentation of the Used PB Beverages  
The acidity values of the control and fermented PB beverages are presented in Table 2. The titutable acidity of the control beverages showed a very small concentration of lactic acid equivalent (0.07% and 0.08%) while pH was close to neutral (oat drink with pH 7.05) or slightly basic (almond drink with pH 7.99). After 48 h of fermentation with the LAB strains, the titutable acidity significantly increased in both beverages to values of 0.47-0.76% and 0.53-0.73% of lactic acid equivalent in the out and almond drink, respectively. The final pH of the produced beverages was below pH 3.5 in all samples, with a higher concentration of hydrogen ions in the oat drinks (the determined pH ranged from 2.80-2.90). In the almond beverages, the pH values were higher and reached values of 3.13-3.42. This indicates a higher concentration of dissociated acids (such as lactic, citric, and succininic) in the fermented oat beverages. For the almond drinks fermented by _L. plantarum_ strains, the low pH was accompanied by significantly higher values of titutable acidity, which also indicates a greater content of undissociated acids, such as free amino acids and free fatty acids. Acidification to pH below 4.5 is a typical symptom of LAB fermentation and achievement of a final lactic acid bacteria density higher than 8 log CFU/g ([PERSON], 2017). _L. plantarum_ is especially responsible for the high acidity of fermented products ([PERSON], 2017). Based on LAB bacterium and the type of fermentation (homo- or hetero-), the accumulation of only lactic \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multicolumn{6}{c}{**Oat Beverage**} & \multicolumn{6}{c}{**Almond Beverage**} \\ \cline{2-9}  & \multicolumn{2}{c}{**Inoculation Stage**} & \multicolumn{2}{c}{**After Fermentation (48 h)**} & \multicolumn{2}{c}{**Inoculation Stage**} & \multicolumn{2}{c}{**After Fermentation (48 h)**} \\ \cline{2-9}  & **LAB** & **Yeast** & **LAB** & **Yeast** & **LAB** & **Yeast** & **LAB** & **Yeast** \\ \hline control & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 \\
1 & \textless{}2\textless{}104 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 \\
2 & \textless{}10\textless{}104 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}2.2\textless{}104 & \textless{}10 & \textless{}10 & \textless{}10 \\
3 & \textless{}10\textless{}104 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 \\
4 & \textless{}10 & \textless{}2.0\textgreater{}103 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 \\
5 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 \\
6 & \textless{}10 & \textless{}2.0\textgreater{}103 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 \\
7 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 \\
8 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 & \textless{}10 \\ \hline \hline \end{tabular} Control—beverage not fermented; sample numbers correspond with the microorganisms described in the experimental section; the fermentation temperature was 37 \({}^{\circ}\)C for sample 1 and 30 \({}^{\circ}\)C for samples 2–8.  
\end{table} 
Table 1: Lactic acid bacteria (LAB) and yeast counts (CFU/mL) of plant beverages before and after fermentation. acid or lactic and acetic acid occurs. _L.