The effects of fermentation and boiling on the level of hydrogen cyanide in Mucuna pruriens (velvet bean)

Abstract

The effects of fermentation and boiling on the level of hydrogen cyanide in Mucuna pruriens (velvet bean) were investigated. Qualitative phytochemical analysis of Mucuna pruriens revealed the presence that tannins, saponins, cardiac glycosides and cyanogenic glycosides. Quantitative analysis revealed that raw Mucuna pruriens contained 42.10 mg/kg hydrogen cyanide (HCN). The respective fermentation and boiling treatments given to Mucuna pruriens significantly reduced the HCN level in the bean. Fermentation for 4 days reduced the HCN concentration to 8.10 mg/kg (33.25%), while boiling for 60 min reduced it to 26.70 mg/kg (36.38%). Combined 4 days fermentation and 60 min boiling treatments significantly reduced the level of HCN in the bean to 18.85 mg/kg being more effective than its respective fermentation or boiling method in reducing the HCN content by 55.23%. Microorganisms involved in the fermentation were bacteria (Proteus spp, Bacillus spp and Pseudomonas spp) and fungi (Saccharomyces spp, Penicillium spp and Rhizopus, spp). The result showed that a combined 4 days fermentation and 60 minutes boiling treatment was more effective in reducing the level of hydrogen cyanide in Mucuna pruriens to safe levels allowed in human and livestock feeds.

Keywords: Boiling, fermentation, hydrogen cyanide, Mucuna pruriens, velvet bean