Cassava; an all-round delicacy

Although it seems like we have been eating it forever, Cassava, also known as manioc or yucca originated in South America and due to its drought resistant nature and ability to grow in poor soils, spread throughout the tropics and eventually on to the South Pacific as well as to all of tropical Africa.

Cassava is one of the staple foods in the diet of many Ugandans, with both the tubers and leaves being eaten. Locally, Cassava is cooked in various ways. One of these is simply boiling the tuber. When boiled, cassava can be eaten on its own or served with beans, meat, groundnuts or other sauces. When it is chopped and mixed with beans, it makes up the dish popularly referred to as katogo.

The other popular method of cassava root preparation is frying. The skin of the root is removed and the remains are cut into small bite-size chunks that can be soaked in water to aid in frying. This fried cassava is a very common street food as it is relatively cheap to buy, easy to prepare and healthy to eat.

Cassava can also prepared by deep frying, grilling or ash-baking. Such is famously sold at the River Kafu crossing en route to northern Uganda.

Sombé, a dish made out of young, green leaves of cassava is popular in some parts of Africa especially Eastern DR Congo. It is also eaten in Uganda. To prepare Sombe, the cassava leaves are washed with hot water, pounded in a wooden mortar. The pounded leaves are then put in a large covered pot and boiled for about 40 minutes.

In the boiling process, the pot or pan is not covered to enable release of hydrocyanic acid (HCN) which is poisonous to the body. It is covered when ingredients such as oil, onion,green pepper,red pepper, fish among others are added, and opened as needed for stirring. This lasts for another hour before serving with cassava bread ,rice among other dishes.

The young tender cassava leaves have high amounts of Vitamins A and C. The leaves also contain iron, calcium, magnesium and potassium and are a source of dietary proteins and vitamin K. Vitamin-K has a potential role in bone mass building.

Cassava roots are a good source of energy and a moderate source of some of the valuable B-complex group of vitamins such as folates, thiamin, pyridoxine (vitamin B-6), riboflavin, and pantothenic acid.

The cassava root also contains some important minerals like zinc, magnesium, copper, iron, and manganese. In addition, it has adequate amounts of potassium (271 mg per 100g). Potassium is an important component of cell and body fluids that help regulate heart rate and blood pressure.

However, cassava when eaten as a root vegetable has to be properly cooked for detoxification purposes before being eaten.

Cassava contains the potentially toxic compounds, cyanogenic glucosides. If present in sufficient quantities, these compounds can cause acute cyanide poisoning and death in man and animals.

The cyanogenic glucosides of cassava (Linamarin and Lotaustralin) on hydrolysis releases hydrocyanic acid (HCN). The toxicity of cassava has long been known and many traditional methods exist to reduce the concentration of cyanide.

According to the figures presented in the FAO Global Cassava Development Strategy, levels of hydrocyanic acid in cassava leaves can be as high as 2 000 mg/kg of fresh leaves. Chopping and drying the leaves reduces the level by at least 90 per cent within 24 hours of exposure.

The cyanide content of the sweet cassava tubers is mainly located in the skin, therefore, sweet cassava requires peeling and boiling to reduce the cyanide content to non-toxic levels. The bitter cassava varieties are usually grated or chopped finely and allowed to soak in water where fermentation occurs, converting the cyanogenic glucosides into cyanide which is released in the environment. Drying for storage purposes and boiling will further detoxify the tubers. Only young leaves of the cassava plant are eaten and they require boiling prior to consumption.

Additional information from http://www.foodsafety.ksu.edu ; http://www.fao.org
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