Comparison of three cyanogen assays for total cyanogens in cassava (Manihot esculenta Crantz)

The sensitivity and reproducibility of three methods for determining the total cyanogenic potential (CNp) of 7 fresh and processed cassava varieties were determined and compared. The total cyanogen content of fresh cassava roots and three cassava products (kondowole, makaka, and starch) were analysed by the acid hydrolysis, microdiffusion with solid state detection and Cooke's enzymatic assays. The total cyanogen contents of the cassava, obtained by the three methods were not significantly different (p<0.05). For example, the CNp of a low cyanogen containing variety, Mwaya were 18.9+or-1.6, 20.3+or-0.4 and 20.4+or-1.4 mg HCN eq. kg-1 fresh weight by Cooke's, acid hydrolysis and solid state methods, respectively. However, at very low cyanogen levels, less than 5 mg HCN eq. kg-1 fresh weight, the acid hydrolysis method overestimates by 3-5 times. Otherwise, their coefficients of variations are very similar, <10%. The acid hydrolysis and solid state methods are cheap and the latter can be used under field conditions to screen for low or high cyanogenesis. They are strongly recommended for use in laboratories in the developing countries.