Influence of alkaline fermentation time on in vitro nutrient digestibility, bio- & techno-functionality, secondary protein structure and macromolecular morphology of locust bean (Parkia biglobosa) flour

Present investigation aimed at evaluating the variation in anti-nutritional factors, phytochemical constituents, bio-functional and technological attributes of locust bean (Parkia biglobosa) flour after alkaline fermentation treatment for different time periods (0, 24, 48 and 72 h). Significant reduction (p < 0.05) in phytate (12.59–5.16 mg/g), saponin (6.87–1.92 mg/g) and tannin (2.86–1.03 mg/g) contents was observed linearly with the fermentation time. Furthermore, in vitro starch and protein digestibility were found to increase from 5.29 to 24.82 g/100 g and 66.47–74.29 g/100 g respectively in response to treatment time. ATR-FTIR spectrum in Amide II region (1600-1700 cm−1) revealed that β-sheet structure prevailed in raw and fermented flours; however, there was significant increase in the α-helix and random coils. Scanning electron micrographs and X-ray diffractograms presented degradation of granular integrity of starch and three-dimensional protein networking. These compositional and structural changes lowered the hydration and emulsification potential while oil absorption and water solubility were found to enhance from 0.86 to 1.01 g/g and 3.16–10.41% respectively. Pearson's correlation matrix showed significant relationship among anti-nutritional factors and nutrient digestibility while principal component analysis validated the differences among variables and observations through two key components of 75.85 and 22.44% respectively.