Abstract

Cassava leaves are largely consumed as vegetable in African, but contain a toxic compound, cyanide. To ascertain their safety and contribution to human nutrition, after a number of pre-treatments preceding their boiling in water, cyanide, vitamin C, β-carotene, crude protein, iron, calcium, phosphorus, potassium and zinc contents were assessed in leaves from bitter, sweet and wild cassava species, boiled for 15 and 30 min after differently processed by: (1) pounding un-dried (UND), (2) drying before pounding (DBP) and (3) drying after pounding (DAP). Blanching headed drying was done in a tunnel solar dryer. Results showed that cassava species, processing procedures, and boiling time significantly (p < 0.05) reduced cyanide and the nutrients. However, except vitamin C, eliminated to almost nil, other nutrients were retained at considerable levels. Sensibly decreased by drying and/or boiling, cyanide levels ranged from 32 - 50 mg HCN/kg (dry matter basis) after boiling for 30 min. These levels, above the recommended level (10 mg HCN/kg) for foods, were safe with regard to cyanide toxicity based on the fact that the vegetable is served in small quantities as side food. consumed quantities of relishes as side foods. Nevertheless, it was advisable not to make them the everyday foods, especially to lower body weight such as children, and to extend time of cooking.

Key words: Cassava leaves, cassava species, processing procedures, cyanide and nutrients, Rwanda.