Influence of controlled fermentation on the nutritional composition, antinutritional factors, and protein digestibility of Bambara groundnut flour

Abstract:

Bambara groundnut (Vigna subterranea L. Verdc.) is a nutritionally rich yet chronically underutilized legume with substantial potential for addressing food and nutrition insecurity across sub-Saharan Africa, but its broader adoption in human diets is limited by significant antinutritional factors and low protein digestibility in unprocessed flour. This study investigated the effects of controlled natural fermentation (CNF) at two temperatures (30 °C and 37 °C) and three fermentation durations (24, 48, and 72 h) on the proximate composition, antinutritional factor (ANF) profile, and in vitro protein digestibility (IVPD) of Bambara groundnut flour. Unfermented flour served as the control. A 2 × 3 factorial randomized complete block design with three replications was used. Results revealed that fermentation significantly (p < 0.01) altered all nutritional and antinutritional parameters. At 37 °C for 72 h, protein content increased from 19.8% (control) to 25.6%, crude fat increased from 5.4% to 6.8%, and ash content improved marginally. Phytic acid was reduced by 76.4%, condensed tannins by 68.2%, oxalate by 71.8%, and trypsin inhibitor activity (TIA) by 81.3% relative to unfermented flour, following 37 °C/72 h fermentation. In vitro protein digestibility improved from 62.4% in control flour to 81.7% under the 37 °C/72 h treatment, a 30.9% improvement attributable to the combined effects of ANF reduction and partial proteolytic activity of fermenting microorganisms. These findings substantiate the effectiveness of controlled fermentation as an affordable, low-technology processing strategy to enhance the nutritional quality and protein bioavailability of Bambara groundnut flour for integration into complementary foods, weaning formulations, and fortified flour blends in Ghana and West Africa broadly.