Fermentation of locust bean (Parkia biglobosa): modulation in the anti-nutrient composition, bioactive profile, in vitro nutrient digestibility, functional and morphological characteristics

Abstract

The present investigation was undertaken with an objective to assess the impact of fermentation temperatures (22, 30, 38 and 46 °C for 72 h) on physico-chemical, functional and structural characteristics of locust bean (Parkia biglobosa). Alkaline fermentation treatment caused drastic reduction in anti-nutritional factors including tannins (~65%), phytates (~60%) and saponins (~70%) owing to hydrothermal treatment and production of microbial enzymes during fermentation. Furthermore, phytochemical profile and associated antioxidant potential were enhanced due to the breakdown of cell-wall components and polyphenolic complexes, liberating phenolic acids and flavonoids available for extraction. With respect to bioactive properties and in vitro starch and protein digestibility, the most pronounced effect was observed after fermentation at 38 °C for 72 h. The trend was also supported by scanning electron micrographs, which revealed modulation in the macromolecular-structural arrangement. Significant and negative correlation coefficients between anti-nutritional factors and protein digestibility (r > 0.95, P < 0.05) confirmed the degradation of protein–polyphenol matrix. Exposure of hydrophobic regions due to fermentation resulted in altered functional properties including better oil absorption capacity, higher water solubility index, reduced water absorption potential, and lower emulsification and gelation properties. Principal component analysis was further employed to statistically validate the differences among variables and observations.