### Pigment Behavior during Fermentation  
Analysis of pigment content was made during each day of the fermentation process (Figure 4). Pigment identification was made for selected days (0, 3 rd and 7 th day of the process; Figure 5). In the literature, pigments such as carotenoids and betalains are mentioned to be sensitive to low pH values. However, betalains show higher stability at low pH compared to carotenoids [4; 37; 49]. In the presented research, differentiation between lactic acid bacteria strains used on pigment behavior was observed. However, in all tested samples decreases in pigment values were observed. During the fermentation process of betroot juice with _L. brevis_, there was a significant reduction in the betalains content compared to the initial fermentation stage (Figure 4). Conversely, when using _L. plantarum_, the decrease in pigment components (red and yellow pigments) was slower and similar. The yellow pigments in betroot juice exhibited a similar relationship to the red pigments. This could be due to the hydrolyzation process where glucose is obtained from betanin, which is a glucoside, and glucose and betanidin are created. These LAB strains can use this glucose and betanidin as a sugar source. Moreover, _L. brevis_ exhibited a higher increase in bacterial count than _L. plantarum_ in the juices, which could be attributed to the decrease in pigment rather than the total acidity and pH. Figure 4: Kinetic behavior of pigment content. Various indexes (such as a, b, c, d, e and f) within the series have displayed statistically significant differences in values at a level of \(p\) < 0.05. The presence of yellow coloration is associated with the presence of the head colorant vulgaxanthin. It was found in the tested products. Similar results were obtained for fermented beetroot juice by [PERSON] et al. [50] and [PERSON] [51], while [PERSON] et al. [52] did not observe vulgaxanthin in their other study. In the study by [PERSON] and [PERSON] [51], this compound was gone after the 5 th day of red beetroot juice fermentation. The highest correlation was observed between betanin (red pigment), vulgaxanthin-I (yellow pigment), and the day of fermentation, which was related to the pH content (as shown in Figure 3a). [PERSON]'s correlation coefficient values were found to be higher for _L. brevis_ as compared to _L. plantarum_. For juices inoculated with _L. brevis_, the correlation between color coefficient and beetroot pigments was observed to be L* (\(-0.7\)), a* (\(-0.96\)), and b* (\(-0.57\)) (as depicted in Figure 3a). The analysis conducted on the pigment compounds of beetroot juice prior to fermentation revealed the presence of betanin, isobetanin, vulgaxanthin-I, vulgaxanthin-II and other vulgaxanthin compounds (as depicted in Figure 5). Post-fermentation analysis indicated the presence of neobetanin. Across all samples, a slight decrease in betanin and vulgaxanthin-I was observed, while an increase in isobetanin and vulgaxanthin-II was noted. The fermentation process resulted in an increase in neobetanin, which is known to be formed from the double bond formation in betanin or isobetanin. This binding can occur at the same location and lead to the same product [53]. Significant decreases in carotenoid content were observed during the seven-day fermentation process of carrot juices. _L. plantarum_ exhibited a higher decrease initially compared to _L. brevis_, but both strains displayed statistically significant decreases. Notably, juices with _L. brevis_ remained stable after the second day of fermentation, while those with _L. plantarum_ showed fluctuating values until the end of the process (see Figure 5). Figure 5: Pigment identification. Pigment compound analysis revealed the presence of \(\beta\)- and \(\alpha\)-carotene, as well as a small amount of lutein (see Figure 5). Minor decreases were observed for \(\beta\)- and \(\alpha\)-carotene during the process. There were no significant correlations between the content of pigments and individual color factors, regardless of the tested juice.