When is Cassava Poisonous?



There are two kinds of cassava: the sweet and the bitter kinds. The ordinary kind sold in the market is the sweet kind, and the one made into laundry starch is the bitter kind.

The manner of planting, whether horizontal or upside down has nothing to do with its poison. Cassava naturally contains hydrocyanic acid, which is poison to both man and animal. The bitter kind contains more of the poison, but both kinds have it.

In the sweet kind, the poison is concentrated on the bark or skin of the crop, not so much on the flesh or meat. In the bitter kind, the poison is spread out on whole crop.

Weather and environment also have something to do with the cassava's poison content. When there is much nitrogen in the soil, there is more poison in the cassava where potassium in the soil is high, the poison in the cassava is low.

A long dry season increases the cassava's poison content: wet soil as during the rainy season lowers its poison content. Because of this, it is said that cassava contains poison in Summer.

According to scientists, cassava's poison contains more or less 30-150 mg of hydrocyanic acid (a milligram is one part of a thousand grams). If the hydrocyanic acid content is less than 50 mg it will not be harmful to eat. If it will exceed 100 mg. the poison content could be dangerous.

In the ordinary way of cooking, the poison disappears in the sweet kind but in the bitter kind, about 20 mg per kilo remains in the fresh peeled cassava.

According to experts, the amount of hydrocyanic acid in cassava is poisonous from one-half mg (.5 mg) up to 3.5 mg per kilo of the person eating the cassava. Thus, a person who weighs 50 kilos will be poisoned if he consumes one and one-fourth (1 1/4) kilo of bitter cassava. When his stomach begins to ache and he starts vomiting, or his mind becomes confused after eating cassava, then he has been poisoned.

The poison in cassava disappears during cooking, so, cooking cassava as suman is a safe way of eating cassava. Besides, suman preparation entails removal of bark, grating, extracting the juice, before cooking. Grating and extracting the juice already removes the poison, and it is further evaporated during cooking.

Other ways of removing the poison in cassava are: chopping, soaking in water, heating up to 57°C, and exposing in the sun. It is best not just to steam it but to cook it well. Even the bitter kind loses its poison when cooked well.

But it is always better to buy the sweet kind. This is known if, upon removal of the bark, the flesh is sweet. The meat of the sweet cassava tastes sweet!

Source: Greenfields December 1980, photo courtesy of www.arafood.com

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