The Effect of Soaking, Boiling and Fermentation with Rhizopus oligosporus on the Water Soluble Vitamin Content of Bambara Groundnut

Abstract

Effect of treatment conditions (soaking, boiling and fermentation with Rhizopus oligosporus (SBF)) on the water soluble vitamins and trypsin inhibitor of bambara nut flour (Vigna subterranea (L) Verdc) was investigated. It was observed that the thiamine content decreased by 5%, riboflavin 6.2%, folacin 9.6%, niacin 10.2% and biotin 14% after 24 h of soaking at room temperature. Treatment by boiling for 45 min revealed that there was a further decrease of 52.4%, 56.2%, 35.0%, 70.0% and 48.3% in the values of thiamine , riboflavin, folacin, niacin and biotin respectively. However, fermentation with Rhizopus oligosporus for 24 h significantly reduced the thiamine content from the original value of 0.47+0.13-0.1 9+0.02 mg/100g, while riboflavin content increased significantly from 0.15+0.06-0.17+0.01 mg/100 g, folacin 0.16+0.02-0.23+0.03 mg/100 g, niacin 1.88+0.09-2.16±0.00 mg/100 g and biotin 0.10+0.02-0.16±0.05 mg/100 g (P < 0.05). Trypsin Inhibitor Activity (TIA) decreased by 22.1% after soaking for 24 h at room temperature and further decreased by 72% after boiling for 45 mins. Conversely, during fermentation period of 24 h, the TIA increased significantly from 0.71+0.62-1.33±0.59 mg/100 g protein (P < 0.05).