## 3 Results and Discussion
### Color Changes  
The results of color determination are summarized in Table 5. As can be noted, the addition of FG had a significant effect on the color parameters, i.e., L*, a*, b*, while it did not significantly affect the color saturation (C) and the hue (h). The addition of FG as well as MP caused a significant increase in the L* parameter (brightness) (\(p<0.05\)). The cooling storage of FWB resulted in a decrease in brightness for WMP and WFG1 and no significant changes in this parameter for the fermented whey (W) and the sample containing 1% flaxseed gum (WFG2). The redness/greenness parameter (a*) of the W sample did not change during storage (\(p>0.05\)). In the case of the WMP variant, fluctuations in the a* parameter during storage were generally statistically insignificant (\(p<0.05\)). When analyzing the color of the WFG1 and WFG2 samples, an initial stabilization of this parameter was observed until the third week and second week of storage, respectively, and a subsequent increase in the value of a*, respectively, by 0.49 and 0.56 units. The W and WMP samples differed significantly in the a* parameter, and the addition of FG increased its value in the WFG1 and WFG2 samples (\(p<0.05\)). The b* parameter (yellowness/blueness) during cold storage of FWB ranged from 2.32 \(\pm\) 0.11 (sample W on day 1) to 5.76 \(\pm\) 0.39 (sample WFG2 on day 14). The highest value of parameter b* was noted for the WMP sample and the lowest for sample W. Yellow-greenish coloration is characteristic for whey due to the presence of riboflavin [1; 2; 13]. All the samples differed significantly in the b* parameter until the second week of storage; in the following two, there was no significant difference in the b* parameter between the samples containing the addition of FG (WFG1 and WFG2). The addition of FG caused a significant color change toward yellow (\(p\) < 0.05). The increase in the L* parameter in samples with FG can be linked to lower particle size, thus higher light scattering [22; 26]. On the first day, the color differences (\(\Delta\)E) between the fermented whey (W) and the other variants of FWB, i.e., WMP, WFG1 and WFG2, were 16.59 \(\pm\) 2.48, 22.17 \(\pm\) 0.62 and 23.49 \(\pm\) 0.17, respectively. The \(\Delta\)E for the samples containing the addition of FG (WFG1 and WFG2) and WMP was higher than 1 (which is considered as perceptible for the human eye), indicating a clear color difference between the samples [28]. The highest color saturation (C) on the first day was found in the WMP sample (6.71 \(\pm\) 0.39), whereas the lowest was noted for the W sample (3.73 \(\pm\) 0.07). Significant fluctuations of the C value during storage and an overall decrease for the WMP and WFG2 samples, at the same level (by 0.11), were found. The color saturation in the W sample did not change significantly (\(p\) > 0.05) during the 3 weeks of storage, but on day 28, a significant increase was observed (0.52) (\(p\) < 0.05) when compared to the initial value. The overall increase in color saturation (by 0.08) was also found in the WFG1 sample (\(p\) < 0.05). The refrigerated storage of the experimental samples was associated with an increase in the h parameter for the W sample (by 0.12) and a decrease for the WMP, WFG1 and WFG2 samples by 0.17, 0.09 and 0.15, respectively.