[masraum]

Originally Posted by gacook

I've had that very same question about a lot of the things we eat, especially various vegetables/roots.

This one always gets me. You've got to wonder how many people got sick or died before they figured out the safe way to prepare the stuff.

The plant with the common names cassava, Brazilian arrowroot, manioc or tapioca is extensively cultivated as an annual crop in tropical and subtropical regions for its edible starchy tuberous root, a major source of carbohydrates.

Cassava must be properly prepared before consumption, as improper preparation of cassava can leave enough residual cyanide to cause acute cyanide intoxication, goiters, and even ataxia or partial paralysis.

From https://en.wikipedia.org/wiki/Cassava

Cassava roots, peels and leaves should not be consumed raw because they contain two cyanogenic glucosides, linamarin and lotaustralin. These are decomposed by linamarase, a naturally occurring enzyme in cassava, liberating hydrogen cyanide (HCN).

Cassava varieties are often categorized as either sweet or bitter, signifying the absence or presence of toxic levels of cyanogenic glucosides, respectively. The so-called sweet (actually not bitter) cultivars can produce as little as 20 milligrams of cyanide (CN) per kilogram of fresh roots, whereas bitter ones may produce more than 50 times as much (1 g/kg). Cassavas grown during drought are especially high in these toxins.

Societies that traditionally eat cassava generally understand that some processing (soaking, cooking, fermentation, etc.) is necessary to avoid getting sick.

Brief soaking (four hours) of cassava is not sufficient, but soaking for 18–24 hours can remove up to half the level of cyanide. Drying may not be sufficient, either.

A safe processing method used by the pre-Columbian people of the Americas is to mix the cassava flour with water into a thick paste and then let it stand in the shade for five hours in a thin layer spread over a basket. In that time, about 83% of the cyanogenic glycosides are broken down by the linamarase; the resulting hydrogen cyanide escapes to the atmosphere, making the flour safe for consumption the same evening.

The traditional method used in West Africa is to peel the roots and put them into water for three days to ferment. The roots then are dried or cooked. In Nigeria and several other west African countries, including Ghana, Benin, Togo, Ivory Coast, and Burkina Faso, they are usually grated and lightly fried in palm oil to preserve them. The result is a foodstuff called gari. Fermentation is also used in other places such as Indonesia (see Tapai). The fermentation process also reduces the level of antinutrients, making the cassava a more nutritious food.