## 3 Results and Discussion  
### Determination of the Physicochemical Properties of Legume-Derived Beverages  
The fermentation of plant-based materials constitutes a multifaceted bioprocess, yielding diverse metabolites that exert an influence on the physicochemical characteristics and functional attributes of the resultant products [31]. A principal alteration within the food matrix during this transformative process was manifested as fluctuations in the initial pH level. Across all the beverage variants, the most substantial reduction in pH occurred after 48 h of incubation (Table 1). The lowest pH value (4.82 \(\pm\) 0.013) was observed in the final products derived from chickpeas (Ch) obtained after 72 h of fermentation (final products). Conversely, beverages derived from green lentils (GL) exhibited the highest pH levels after both 48 h and 72 h of incubation. The obtained results correspond to the findings described by [PERSON] et al. [32]. The authors analyzed seven strains of Lactobacillus as potential starter cultures for the fermentation of beverages produced from lentil grains. Notably, their outcomes revealed that all the examined strains exhibited the capacity to ferment the pulse-derived substrate within 24 h. However, it was observed that only three strains, namely, Lactobacillus acidophilus ATCC 4356, Lactobacillus fermmentum DSM 20052, and Lactobacillus paracasei subsp. paracasei DSM 20312, exhibited both the desired growth kinetics and the capability to effectively reduce the pH level. It is noteworthy that the final pH of fermented legume-derived raw material is contingent not solely upon the acidification capacity of lactic acid bacteria (via organic acid production). Rather, it is also influenced by intricate biochemical transformations and the activity of bacterial proteolytic systems, which liberate alkalizing compounds from native proteins, thereby modulating the pH level [33]. The probiotic fermentation applied in this study significantly decreased the total extract content (TEC) of all the legume-based beverages (Table 1). The most pronounced changes, compared to the control, were observed in the final products (after 72 h of fermentation) of the RL variant. The highest TEC (2.26 \(\pm\) 0.279 \({}^{\circ}\)Brix) was noted in the final products derived from chickpeas. The findings suggest that the applied pasteurization process may also have contributed to the reduced values of the measured parameter in the beverages, except for the GL variant (Table 1). The decline in TEC may be attributed to bacterial metabolic activity, which facilitates the conversion of carbohydrates into lactic acid (associated also with decreasing pH). Interestingly, the capacity of certain lactic acid bacteria to synthesize and excrete extracellular polysaccharides (exopolysaccharide, EPSs) may also contribute to the reduction in TEC levels in fermented products [34], since EPSs augment the viscosity of fermented products through interactions with proteins and carbohydrates, consequently leading to a decrease in TEC. Since \(L\). _plantarum_ has been documented as a producer of exopolysaccharides [35], it might be expected that its EPSs were also produced during the fermentation of the legume-based beverages, thereby contributing to the modification in the TEC levels in the products. Moreover, the variations observed in the analyzed parameters among the different beverage variants may be linked to the differential preferences of the tested strain in metabolizing specific constituents present in diverse legume raw materials. This was proved by [PERSON] et al. [36] in an investigation examining soy beverages fermented by probiotic strains of _S. thermophilus_ and \(L\). _bulgaricus_.