## 4 Discussion
In addition, other phenolic acids, such as caffe acid and ferulic acid, were detected in smaller amounts within a few hours of fermentation, indicating possible conversion between phenolic acids via chalcones. The simpler structure of these metabolites may contribute to the higher antioxidant activity of fermented jussar pulp, with an increase in oxygen radical-reducing capacity from 49.2 to 90.7% compared to the unfermented extract. Accordingly, _L. plantarum_ and _Oenococcus oeni_ deglycosylateanthocyanin glucosides into their aglycones: malvidin, delphinidin, and peonidin. Further ring cleavage released trihydroxybenzaldehyde and syringe acid (from malvidin), gallic acid (from delphinidin or demethylation of syringic acid), or vanillic acid (from peonidin) [49; 66]. The degree of anthocyanin degradation by lactic acid bacteria depends on the LAB species. The highest anthocyanin content was observed by conducting fermentation in the presence of _L. casei_ and _L. bulgarcius_; meanwhile, conducting fermentation in the presence of other _L. species_ resulted in anthocyanins at lower levels. In addition, the anthocyanin content, particularly delphinidin 3-O-glucose, in the fermented orange juice was more significantly reduced by _L. rhamnus_ or _L. paracisei_ than by _L. plantarum_ or _L. brevis_. These observations may be due to variability in \(\beta\)-glucosidase or \(\beta\)-galactosidase activity, and the presence of more hydroxyl groups in delphinidin increases its susceptibility to enzymatic degradation than that of other anthocyanins [67; 68]. Of the kinetic models adopted, follow-up reaction equations and first-order equations best described the time-dependent changes taking place. On the other hand, the following reaction equations were best suited to explaining the generation and disappearance of lactic acid (LA). This research demonstrates that the process function values of AA and LAe are reliant on the LAB strain and plant material content, whereas the rate of change of TPC may be heavily influenced by the types of phenolic compounds generated during fermentation. In addition, the highest rate of lactic acid growth (with the lowest rate of LA disappearance) is characterised by the process for obtaining FSE-5. In addition, the best ratio of the lactic acid growth constant to the LA disappearance constant occurs when using an initial sugar content of 3.20%. Moreover, changes in the values of the main functions describing the process, AA and TPC, do not depend on the type of LAB strain used in the fermentation process. Their nature is typical of the diffusive transfer of active components with antioxidant potential contained in the plant raw material (and resting on antioxidant activity) in the solution, with simultaneous transformation of flavonoids (such as apigenin, kaempfer, luteolin, quercetin, and taxifolin) contained in the raw plant material undergoing transformation to free phenolic acids during fermentation (i.e., caffe acid, gallic acid, ferulic acid, p-coumaric acid, sinapic acid, and vanillic acid), which are metabolic products (Figures 1-6, Tables S1 and S2). Fermentation is one of the methods used to increase phenolic acid content. When conducting fermentation of plant raw materials, the biotransformation of phenolic compounds (such as apigenin, kemferol, luteolin, quercetin, taxifolin, flavonoids, tannins, stilbenoids, lignans, and alkylresorcinols) via lactic acid bacteria occurs. During fermentation, anthocyanin aglycones (i.e., anthocyanin) such as malvidin and peonidin are released, which are then converted to syringe acid and vanillic acid. Flavonols found in plant materials in monomeric form (catechin, epicatechin, epigallocatechin, and gallocatedin) or polymeric form (proanthocyanidins or condensed tannins) are converted into their free forms during fermentation. Catechin and epigallocatechin gallates are converted to catechchin and epicatechin. In addition, epigallocatechin gallate is converted to free catechin, catechin esters, and gallic acid.