# The Fermentation of Orange and Black Currant Juices by the
## 3 Results and Discussion
### Parameters of the Fermented Juices  
The selected organic acids and sugars concentration in the samples after fermentation are shown in Tables 2 and 3. After the orange juice fermentation, the samples contained only minor residual fructose (up to 0.73 \(\pm\) 0.05 g/L for the sample with DAP added), while the glucose concentrations were below the detection levels. These results are indicative of the fully fermented samples. Perhaps even a shorter fermentation time of less than 7 days should be considered. The predominant organic acid in the juices fermented by _S. bayanus_ and _S. cerevisiae_ var. _boulardii_ yeasts was citric acid. Its concentration in the fermented orange juice ranged from 6.96 \(\pm\) 0.26 to 7.81 \(\pm\) 0.24 g/L. The concentration of this acid in the non-fermented orange juice was equal to 8.51 \(\pm\) 0.57 g/L. Considering the statistics (\(p\) < 0.05), it can be concluded that there was a slight reduction in the citric acid concentration only for the OR + DAP and OR \"0\" samples, while in the case of the glucose-added samples, regardless of the yeast used, the loss of citric acid concentration was not statistically significant (\(p\) > 0.05). The malic acid concentration ranged from 1.21 \(\pm\) 0.10 to 3.12 \(\pm\) 0.17 g/L, while the succinic acid concentration ranged from 0 to 0.55 \(\pm\) 0.02 g/L. When we compare these results with the levels of acids in the juices before fermentation, it can be seen that the concentrations of both acids decreased (\(p\) < 0.05) for the fermented samples with DAP supplementation and increased (\(p\) < 0.05) for the samples with glucose supplementation. In contrast, for the samples fermented without glucose and DAP supplementation (OR \"0\"), the malic acid and succinic acid concentrations remained at levels similar to those in the unfermetrand orange juice. [PERSON] et al. described that, in the case of citric and malic acid in orange \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & **CIT Acid** & **MAL Acid** & **SUC Acid** & **GLU** & **FRU** \\ \cline{2-6}  & & & **[g/L]** & & \\ \hline OR “0” & 7.05 \(\pm\) 0.32 & 2.50 \(\pm\) 0.17 & 0.18 \(\pm\) 0.01 & n.d. & n.d. \\ OR + DAP & 6.96 \(\pm\) 0.26 & 1.21 \(\pm\) 0.10 & n.d. & n.d. & 0.73 \(\pm\) 0.05 \\ OR + G & 7.81 \(\pm\) 0.24 & 3.09 \(\pm\) 0.14 & 0.55 \(\pm\) 0.02 & n.d. & 0.17 \(\pm\) 0.01 \\ OR Sb + G & 7.62 \(\pm\) 0.26 & 3.12 \(\pm\) 0.17 & 0.45 \(\pm\) 0.03 & n.d. & 0.04 \(\pm\) 0.01 \\ \hline n.d.—not detected. & & & & & \\ \end{tabular}
\end{table} 
Table 2: Organic acids, glucose, and fructose concentrations in the orange juice after fermentation. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & **CIT Acid** & **MAL Acid** & **SUC Acid** & **GLU** & **FRU** \\ \cline{2-6}  & & & **[g/L]** & & \\ \hline BC “0” & 4.90 \(\pm\) 0.27 & 0.31 \(\pm\) 0.01 & 0.50 \(\pm\) 0.02 & n.d. & n.d. \\ BC + DAP & 5.15 \(\pm\) 0.28 & 0.30 \(\pm\) 0.01 & 0.13 \(\pm\) 0.01 & 0.92 \(\pm\) 0.06 & n.d. \\ BC + G & 6.04 \(\pm\) 0.22 & 0.30 \(\pm\) 0.02 & 0.71 \(\pm\) 0.03 & 1.04 \(\pm\) 0.06 & 1.58 \(\pm\) 0.06 \\ BC Sb + G & 6.75 \(\pm\) 0.27 & 0.28 \(\pm\) 0.01 & 0.89 \(\pm\) 0.04 & 0.74 \(\pm\) 0.04 & 0.95 \(\pm\) 0.04 \\ \hline n.d.—not detected. & & & & & \\ \end{tabular}
\end{table} 
Table 3: Organic acids, glucose, and fructose concentrations in the black currant juice after fermentation. juice, there was an increase of about 20% in their concentrations during fermentation by _S.cerevisiae SC-125_ yeast [31]. The samples after the fermentation of the black currant juice contained small amounts of glucose (up to 1.04 \(\pm\) 0.06 g/L for the glucose-supplemented juice) and fructose (up to 1.58 \(\pm\) 0.06 g/L for the glucose-supplemented juice), which may indicate incomplete sugar attenuation due to the too short a processing time or low resistance of the tested strains to the compounds present in black currant juice.