Functionalization of pre-gelatinized Urad bean fermented by Saccharomyces cerevisiae MK-157 as a fat replacer and its impact on physico-chemical, micromorphology, nutritional and sensory characteristics of biscuits

The reduction of saturated fats in baked products has become an important unit operation in the food industry due to the consumers' demand for healthy foods low in saturated fat. In this research, a comprehensive biotechnological technique was explored to enhance the functional, technological, and nutritional characteristics of Urad beans as a fat replacer in biscuits via the combined treatment of gelatinization and fermentation by Saccharomyces cerevisiae MK-157. Fat in biscuits was replaced with fermented and gelatinized Urad bean flour (FGUBF) by S. cerevisiae MK-157 in the following proportions: 10%, 20%, and 30% wt/wt. The peak, final, breakdown, and setback viscosities of flour blends decreased. Protein, ash, crude fiber, antioxidants (DPPH, FRAP, ABTS, hydroxyl scavenging), bioactive compounds (total phenol content (TPC) & total flavonoid content (TFC)), and α-glucosidase inhibition increased, with the level of fat replacement in flour blends and their biscuits. However, FGUBF reduced the ash (4.32%) and fiber (10.96%) contents compared to the control sample (5.11% and 20.32%, respectively). The TPC and TFC of flour blends increased from 35.49 to 90.01 mg GAE/100 g and from 20.83 to 60.45 mg CE/100 g, respectively. However, baking decreased the values of TPC compared to flour blends, whereas TFC increased, and a similar increase in antioxidant activities was observed for fat-replaced biscuits. Phytic acid and total saponins were drastically reduced after fermentation by 98.83% and 98.85%, respectively. The microstructure of biscuits showed disoriented arrangements of protein, starch, fiber, and their complexes with disrupted gluten networks. Fermentation enhanced the In vitro protein digestibility (74.91 to 89.21%) of samples. Biscuits prepared from 20% FGUBF demonstrated desirable dimensional, textural, and sensory properties compared to control biscuits. Based on the results of this investigation, FGUBF might be recommended as an important natural fat substitute with enhanced nutrient bioavailability, antioxidants, and bioactive compounds for functional foods and nutraceuticals.