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+0.13-0.19+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).