Fermentation Reduces Cyanide Content during the Production of Cassava Flours from Sweet and Bitter Cassava Tuber Varieties

Abstract

Sweet and Bitter Cassava tubers were fermented for production of cassava flours. The samples were peeled, washed with potable water and cut into slices of 5-6 cm length. They were steeped separately in water to ferment spontaneously for 4 days. The samples were serially diluted and 0.1 ml aliquot inoculated on appropriate media and incubated for isolation of bacteria and fungi. Physico-chemical, cyanide and proximate status of the fermented samples were determined. Staphylococcus aureus, Lactobacillus spp., Bacillus spp., Klebsiella spp., Corynebacterium spp., Aspergillus niger, Penicillium, Mucor, Rhizopus and Candidia species were isolated. Lactobacillus, Bacillus and Candida species remained till the end of fermentation. Sweet cassava had total viable bacterial counts range: 3.6 x 102 - 4.1 x 105cfu/ml; coliform counts: 2.7 x 102cfu/ml - 3.5 x 105cfu/ml and fungal counts 1.6 x 102cfu/ml - 2.3 x 105cfu/ml while bitter cassava had total viable bacterial counts: 3.3 x 102 - 3.7 x 105cfu/ml; coliform counts: 2.3 x 102 - 3.2 x 105cfu/ml and fungal counts of 1.3 x 102 to 2.1 x 105cfu/ml. Titratable acidity of both cassava samples increased after fermentation while the hydrogen cyanide and pH decreased after fermentation in both cassava tubers varieties. Fermentation reduced the cyanide content in both cassava varieties flours to acceptable limits and eliminated food borne pathogens from the floors thus making the cassava flours safe for human consumption.