Reduction of the cyanide content during fermentation of cassava roots and leaves to produce bikedi and ntoba mbodi, two food products from Congo

Abstract

Cassava roots and leaves constitute energy-rich and protein-rich foods, respectively, for the 
populations in Central Africa, where they are consumed as staple foods. But cassava roots and leaves 
contain some cyanide in the form of cyanogenic glucosides, notably the linamarine, which can 
constitute a poison for the consumers when roots or leaves are processed improperly. Cassava roots 
and leaves processing in Congo, as in most central African countries, involve fermentation. The 
fermentation of the cassava roots is a lactic fermentation (pH 3.8) with Lactobacillus as dominant 
microflora whereas that of the cassava leaves is an alkaline fermentation (pH 8.5) where Bacillus 
constitute the main microflora. The hydrolysis of cyanogenic glucosides takes place as well in acid 
medium during the cassava tubers fermentation as in basic medium with the cassava leaves 
fermentation. The cyanide content decreases during the fermentation of cassava roots and leaves by 
more than 70% through the activities of the bacterial produced linamarase, allowing the hydrolysis of 
cyanogenic glucosides. Certain lactic bacteria present in the environment of fermentation are resistant 
to the strong cyanide concentrations of between 200 and 800 ppm.