## 3 Results
### Selection of the Optimal BWB Variant  
The assessment of the BWB fermentation process based on chosen quality features enabled the selection of a beverage variant that would constitute the basis for further development of the innovative product. The selection process included several steps, which are presented in Figure 5.  
First, the success of the fermentation process and microbiological quality were assessed based on LAB amount and pH value. In most BWB variants, the LAB amount reached the satisfactory level of 10\({}^{8}\) CFU/mL after 8 h of fermentation. The LAB number will determine, among others, the shelf life and health benefits of the product, so this value should be as high as possible. Therefore, the best variants are BWB with flaxseed fermented with _L. plantarum_ for 48 h and BWBs without and with flaxseed fermented by _L. paracasei_ for 24 h, in which the LAB count reached 10\({}^{9}\) cfu/mL. Statistical analysis confirmed the significantly higher LAB amount in these variants, although the LAB number in BWB with flaxseed fermented by _L. paracasei_ for 24 h and BWB without flaxseed fermented with the LAB mixture for 24 h did not differ significantly. The second quality criterion chosen to evaluate the prepared BWBs was the pH value. The appreciable acidity of the beverages indicates that the fermentation process is proceeding correctly and positively affects the microbiological safety and stability of the final product. Therefore, the study assumed that the optimally prepared fermented BWBs should have a pH of \(\leq\)3.5. Obtaining the desired degree of acidity depended on the fermentation time. In most variants, a pH level below 3.5 was achieved after 24 h, except for BWB with flaxseed fermented by _L. plantarum_, where a pH of 3.37 was achieved after 48 h fermentation. The lowest pH values (<3.0) were obtained for BWBs without and with the addition of flaxseed, fermented by _L. paracasei_ and the LAB mixture after 48 h of fermentation. Interestingly, the highest LAB population was not recorded in the BWB variants with the lowest pH. For example, in the BWB with flaxseed fermented  
Figure 5: Selection of the optimal BWB variant based on the adopted assumptions. BWB: bread waste beverages without flaxseed; BWBF: bread waste beverages with flaxseed; Lp: fermented by _L. plantarum_; Lp: fermented by _L. paracasei_; Mix: fermented by a mixture of LAB; 0–48 h: fermentation time. by _L. plantarum_ for 48 h (the highest LAB number), the pH value (3.37) did not differ significantly from BWBs with flaxseed fermented by _L. paracasei_ (3.21) and BWBs fermented with LAB mixture (3.01 and 3.23 with and without flaxseed, respectively) for 24 h, for which LAB amount was significantly lower. The LAB number and pH were used together as the third criterion, emphasizing the economic aspect of the process. As BWBs fermented for both 24 and 48 h had good and comparable quality parameters, it can be assumed that it will be more profitable from a production point of view to carry out fermentation in a shorter time, reducing the production costs. Taking into account these parameters, the optimal variants were BWBs without and with the addition of ground flaxseed, fermented with _L. paracasei_ and a LAB mixture for 24 h.  
The last parameter for selecting the optimal BWB variant was its antimicrobial activity. The results confirmed that to obtain the best functional properties (in the context of antibacterial properties), it is necessary to carry out fermentation for at least 24 h. After this fermentation time, it was possible to determine the MIC values for most variants, and a broader spectrum of the activity of the beverages against indicator microorganisms was observed. Additionally, the conducted research indicated that the ground flaxseed addition resulted in increased antagonistic activity of the fermented BWBs. These observations indicated that adding a nutrient-rich ingredient could increase the product's functional properties.