[Stoves] Removing cyanide from cassava

[Robert Taylor]

Though somewhat off topic, this may be of interest to some on this list 
(from New Scientist magazine,  17 Feb 2007, p 16):

NEW IMPROVED CASSAVA RECIPE REMOVES DEADLY INGREDIENT
Millions of people in Africa depend on cassava for food despite an 
unfortunate bitter ingredient: cyanide.

Although cassava (Manihot esculenta) is processed to remove cyanide, the 
techniques are not always effective. Commonly the plant is ground into flour 
and then mixed in boiling water to create a claggy paste, but this only 
reduces cyanide levels by about 60 per cent. Consequently, each year 
thousands of children across central and east Africa are struck down by 
konzo, an irreversible paralysis of the legs.

"Even in a good year in north Mozambique, cyanide levels [in cassava paste] 
frequently top 45 parts per million, far more than the WHO-recommended 10 
ppm," says Howard Bradbury of the Australian National University in 
Canberra.

Bradbury has now developed a simple technique for removing cyanide that 
could prevent much of the sickness. Cassava flour is mixed with water, and 
the dough spread in a layer no more than 1 centimetre thick, and left in the 
shade for 5 or 6 hours. The process removes almost all of the cyanide (Food 
Chemistry, vol 101, p 894).

It works by bringing together an enzyme in the plant cell walls with the 
cyanide-producing compound linamarin in the cytoplasm. The enzyme breaks 
down the linamarin, releasing hydrogen cyanide gas that then diffuses out.