## 3 Discussion
Even though lactic acid is a well-established antimicrobial agent, the role of acetic acid has recently been found to be more enhanced, insinuating greater effectiveness. In the current study, the concentration of acetic acid reached a value of 1.23 g/Kg, which is the most elevated one compared to other relative studies that our research team performed in recent years [17; 27; 28; 29; 30; 31]. More specifically, in the aforementioned previous research works, the sourdoughs were added in a concentration of 30% \(w/w\) for bread making, with employment of the following: (i) _L. paracasei_ K5, which led to acetic acid with a concentration of 1.13 g/Kg of bread, (ii) _L. plantarum_ ATCC 14917 with or without pomergnanate juice, (iii) _L. paracasei_ SP2, (iv) kefir grains, (v) _L. paracasei_ SP5 free or immobilized and (vi) _L. bulgaricus_ ATCC 11842, which led to acetic acid concentrations varying around lower than or almost 1 g/Kg. Likewise, the rope spoilage appeared on the 13 th day, which is one of the most increased values recorded compared to previous studies. Only in two cases was the appearance of rope spoilage more extended, but there were no statistical differences. Specifically, bread spoilage appeared by approximately the 14 th day of bread storage when sourdoughs were prepared with _L. paracasei_ SP2 and SP5 [29; 31]. Indeed, acetic acid exhibits advanced antibacterial properties against bacteria involved in rope spoilage and is being added alone as preservative in bread production in the form of vinegar [32]. It is noteworthy that three other minor organic acids (formic, n-valeric and caproic acid) embrace elevated functionality against various bread spoilage microorganisms through synergistic effects [29]. It is well known that the basic ingredient of bread, wheat, loses its nutritional value during industrial bread making with regards to proteins, minerals, fiber and antioxidant activity, and this leads to deficiencies. Consequently, the fortification of bread with the addition of various micronutrients (vitamins and minerals) and protein-rich sources is necessary [33; 34]. In this frame, the proposed supplement consisted of fermented Cornelian cherry juice by _L. plantarum_ ATCC 14917, which led to statistically significant increases in TPC and AC levels in the respective bread (BFJ) compared to all the other samples produced. _L. plantarum_ strains have proved their effectiveness in various biotransformation food systems, including bread, by degrading various bound phenols to soluble compounds with increased AC and bioavailability [21; 35]. Interestingly, respectable amounts of TPC and AC levels were also achieved in the case of the BUFJ (compared to the CB), where unfermented juice was applied, without the presence of any LAB, including _L. plantarum_ ATCC 14917. This outcome is in agreement with other researchers who used powder of the whole fruit of Cornelian cherry in bread production. In the current study, the results are more impressive since the sourdough technology and the form of the fruit (juice) fermented or unfermented elevated the TPC and AC levels. The main reason for this outcome is that LAB contained in the wheat flour were activated and enhanced by the phenolic content of the Cornelian cherry juice and afterwards transformed the phenolic compounds present in wheat flour into various new compounds with high antioxidant activity. Generally, the antioxidant activity of fortified breads is mainly derived from the phenolic rather than other compounds present in bread [36]. Specifically, the increase in the antioxidant compounds' content and activity after baking is commonly attributed to the weakening of the cell wall matrix, enabling the release of phenolic acids from bounded forms, and to the decomposition or conversion of complex molecules (tannins, quercetin derivatives and ruin) to simpler phenolic compounds (mostly phenolic acids and quercetin derivatives) [37]. Sourdough seems to enhance even more this effect, resulting in antioxidant protection [13].