## 3 Results and Discussion
### Physical Properties
#### 3.2.2 Color Coefficients of Fermented Samples  
The color of the yellow beetroot was determined by measuring color coefficients such as the lightness (L*), reddish-green (a*), and yellowish-blue (b*) Figure 1.  
Figure 1: Color coefficients: (**a**) lightness; (**b**) redness; and (**c**) yellowness; a, b, c...—mean a statistically significant difference in the selected % through the whole fermentation process (from 0 to 2M); A, B, C...—mean a statistically significant difference for the selected day analyzed for all the tested salt contents (for each series).  
The brightness of the samples was found to remain constant during the fermentation process, which could be due to the initial bright yellow-gold color of the beetroot tissue. Moreover, there were no significant changes in the brightness values observed between the various analyzed salt concentrations, except for the samples stored for more than 2 months with over 2% salt added to the brine, which showed a decrease in brightness (Figure 1a).  
The color parameter a*, which characterizes the proportion of red or green color, showed a shift toward green (negative values of the a* coefficient) (Figure 1b). The fermentation process influenced the perception of the color shades of the fermented samples, with the proportion of green color shifting toward the transition to red (increase from a value of \(-3\) to a value of \(-0.5\)) but remaining within the green color range. This change was evident both in comparison with the raw beetroot (a* = \(-3.7\)) used as a reference material and in analyses within a given salt content (e.g., for a salt content of 2-3%, a* = \(-2.4\) to \(-2.5\)). The duration of the fermentation process significantly influenced the value of this color factor, causing it to increase toward zero. The longer the process, the higher the value of the a* coefficient.  
The proportion of yellow color is the most significant factor for yellow beetroots. In reverse to the red beetroot fermentation study, in this study no change in the brine color was observed during the fermentation process. The analysis of data concerning the color coefficient b* revealed no affect after adding table salt to the brine. However, during the lactic fermentation process, there was a reduction in the b* value, regardless of the salt concentration used. Even in the sample without added salt, there was a 50% decrease in the value of this coefficient after four days of the process (Figure 1c). The samples with added 2% and 3% table salt showed minimal variations in the analyzed concentration. After storage, a further decrease in the color factor b* was observed in the samples, irrespective of the salt concentration used. The yellow pigments in golden yellow beetroot mainly contribute to the amount of color factor b* responsible for the yellowness of the samples.  
Similar results for fresh golden beetroot for the color coefficients were observed in [4]. There is no research on the fermentation of yellow beetroot, so we can only state that the fluctuations in the a* and b* color coefficients are related to the pigment content, small amount of betanin (red colorant) and high amount of vulgaxanthin (yellow colorant) and its behavior during the fermentation process. There is well-known information that betalain pigments are stable in a range of pH (3-7) and can at a low pH transform from betaxanthin into betacyjanin [56; 57; 58].