Optimization of fermentation conditions of synbiotic legume-based beverages and study of their antimicrobial and proteolytic activity.

The objective of the present work is to optimize fermentation conditions for a set of three legume-based synbiotic beverages made from green mung and red kidney beans, namely GMB (100% mung bean); RKB (100% kidney bean); and KB (7:3, kidney bean: mung bean) to attain desirable quality attributes. Face-centered composite design (FCCD) was applied using fermentation time and temperature as independent variables. The responses, namely, pH, protein digestibility (PD), and total viable count (TVC) of probiotic Lacticaseibacillus casei ATCC 335, were optimized using response surface methodology (RSM) followed by numerical optimization. The optimization was based on maximizing the desirability, which connected the responses and importance. The experimental and predicted values were similar, and the model was valid for all beverages with R  > 0.9. The optimized condition suggested that fermentation at 20°C for 18 h in the case of KB and GMB and 21 h for RKB would lead to desired pH (6.0-6.5), maximum PD (> 60%), and highest TVC (> 8 log CFU/ml). A significant reduction in antinutritional factors (ANFs), namely, tannin (20-44%), saponin (43-52%), and phytate (43-46%) from an initial value of around 0.30, 0.40, and 0.50 mg/L respectively, for all the beverages at optimized fermentation conditions was observed. Similarly, a slight loss of < 3.5% in total phenol content (TPC) was seen. Additionally, good proteolytic and antibacterial activity was observed, with KB being the best. Hence, all developed legume-based synbiotic beverages exhibit desirable goals when subjected to optimized fermentation conditions and enhanced functionality. PRACTICAL APPLICATION: When subjected to optimized fermentation conditions, the developed synbiotic legume-based beverages can be used as a potential functional food in the nondairy beverage industry with added health benefits and new tasting flavors.