## 3 Results and Discussion
### Total Phenolics and Antioxidant Activity  
Total phenol content (TPC) of the fermented chokeberry juice was determined using Folin-Ciocalteu method. The results are presented in Table 3.  
Results indicate that the application of lactic acid fermentation through _L. paracasei_ SP5 led to a remarkable increase of TPC in all the studied periods compared with the control unfermented sample. A possible explanation of this result is that lactic acid fermentation metabolites produced by the breakdown of anthocyanins and other larger-in-size phenolic compounds led to this increase in TPC, as it was observed in many other cases with other fruit juices (pomegranate, cornelian cherry, etc.) [7; 11]. However, it is well established that the applied strains for lactic acid fermentation are critical to the variance of the TPC, as well as the starting substrate. Different LAB strains usually follow many metabolic pathways during fermentation of various fruit juices, leading to the metabolism and biotransformation (mainly due to decarboxylation and reduction reactions) of various phenolic compounds [40]. Likewise, strains have different capacities on the metabolism of phenolics. For instance, fermentation of chokeberry with keifr led to an increase of TPC and to bioaccessible polyphenols [24]. In this study, the effect was positive, leading to increased levels of TPC. It has been reported that various enzymatic activities such as decarboxylate can lead to better biotransformation of phenolics and that _Lactobacillus_ strains exhibit this ability [41]. For instance, it has been stated that a _Lactobacillus paracasei_ strain was effective in phenolics bioconversions due to its high content of \(\beta\)-glucose and \(\beta\)-galactosidase [42]. It is noted that more analytical tools can be applied in the near future in order to investigate more accurately the changes in certain groups such as flavonoid glycosides, total quercetin, and hydroxybenzoic acids.  
The changes in the antioxidant activities of unfermented and fermented chokeberry juice with _Lactobacillus paracasei_ SP5 during fermentation at 30 \({}^{\circ}\)C and at 4 \({}^{\circ}\)C were determined through FRAP and \(\alpha\)TEAC assays and are presented in Figure 1a,b. These two assays demonstrated that the antioxidant activity of fermented chokeberry juice showed a significant increase mainly during the first week of fermentation at 4 \({}^{\circ}\)C, which was observed until the end of the storage (fourth week), compared with the unfermented one. This finding is very important since it seems that the nutritional value of the fermented product was enhanced through fermentation. As similarly noted in the literature the application of potentially probiotic strains applied for juice fermentation may lead to an increase of ABTS radical scavenging activity [29]. In addition, _Lactobacillus_ strains may possess high phenolics biotransformation. Likewise, phenolic acids may act as free radical scavengers and possess significant antioxidant activity [43]. Likewise, the increased antioxidant activity of fermented chokeberry juice during fermentation at 4 \({}^{\circ}\)C could be attributed: (i) to the ability of _Lactobacillus paracasei_ SP5 to provide phenolics biotransformation and (ii) simultaneously to its viability, which was maintained at high levels during storage (above 6 log cfu/mL).  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Time** & **Chokeberry Juice Samples** & **TPC GAE g/L** \\ \hline
0 h & Unfermented & 8.5 \(\pm\) 0.1 \\ \hline
48 h & Unfermented & 8.6 \(\pm\) 0.2 2  \\ \hline
1 st week & Unfermented & 8.9 \(\pm\) 0.3 2 [FOOTNOTE:2]Footnote 2: This is not the case for