Mild methods of processing cassava leaves to remove cyanogens and conserve key nutrients

Current methods for processing cassava leaves to remove cyanogens involve pounding followed by boiling in water or boiling intact leaves for 30 min or longer. Boiling in water rapidly removes cyanogens but also breaks down vitamins, proteins and S-containing amino acids, which are necessary to detoxify ingested cyanide. Two methods have been developed to remove cyanogens whilst conserving these key nutrients present in cassava leaves. The first method involves pounding leaves in a pestle and mortar for a minimum of 10 min until the leaves are well macerated, followed by washing the pounded leaves twice in twice their weight of water at ambient temperature, which reduces the total cyanide remaining to 8%. Two further washes reduce the total cyanide to 3%. The second method is to immerse cassava leaves in ten times their weight of water at 50 ± 3 °C for 2 h followed by one change of water and further immersion for 2 h at 50 °C which reduces the total cyanide remaining to 7%.

Research highlights
► Protein, amino acids and vitamins are lost by boiling cassava leaf to remove cyanide.
► Konzo is an irreversible paralysis of the legs in children and young women.
► Konzo is caused by a bitter cassava diet and lack of S-containing amino acids.
► Cyanogens can now be removed by pounding and washing in water at room temperature.
► The green pounded leaves retain key nutrients and may help to reduce konzo.