Cassava is a tropical root crop that requires at least 8 months of warm weather to produce a crop. It is grown in a savana climate but can be grown in extremes of rainfall. In most areas it does not tolerate flooding. In droughty areas it loses its leaves to conserve moisture. It takes 18 or more months to produce a crop under adverse weather- cool or dry. It does not tolerate freezing conditions but tolerates a wide range of PH4.0-8.0 it is most productive in full sun.
Planting: Cassava is planted using 7-30 cm portions of the mature stem as propagules with spacing at 1m by 1m. Stems of harvested cassava are cut and put in holes at a slanting position that exposes the stem nodules to the soil.
Harvesting: The plant can be harvested manually or with a mechanical harvester. Grown plants are harvested at between 9 and 18 months. This spaced harvest regulates supply to the market.
In the Americas and Africa preparation involves grating, removing sap and squeezing or pressing before drying.When left in the press for about 4-5 days, there is some fermentation and also removal of more of the toxicity caused by hydro cyanide content. The fermented flakes give a desirable soar taste.
There are other methods like fermenting the roots in water and then sun drying for storage or grating into a dough that is cooked. Some alcoholic beverages can be prepared from the roots. Harvested brownish tubers are peeled to expose inner whitish parts which are washed and grinded. The grinded paste is bagged into slightly porous bags and weights are put on the bags to squeeze out the water content. This rids the cassava of some of the acidic content.
Leaving the cassava in the bag for three to five days allows a process of fermentation that further reduces the acidic content. There could be a process of sieving out fibers before bagging or after bagging the paste. The fermented product will be passed through a sieve to remove fibers leaving the finer granules. These granules are fried on special earthen or metal pots allowing for gradual steaming and drying further reducing the danger of the acidic content. Other technologies for processing are available and catching on but many prefer the taste given by this type of processing. Industrial processors are available to prepare starch from cassava and larger scale of drying.
Preparation for eating: Peeling followed by boiling, baking or frying are done for the sweet cassava. Bitter cassava should be eaten after due processing because of the presence of hydro cyanic acid – cyanogenic glucosides. These glucosides are reduced to harmless levels through processes described above. The cassava paste can be made into ‘fufu’ and eaten with various soups. It could otherwise be dried into ‘Gari’ which can be taken with cold water or added to boiling water to make ‘eba’(Yoruba name) which some still call ‘Gari’. Gari can be added as hardener to prepared beans for more solid eating. Water is added to be taken as a beverage.
Nutrition: The cassava tuber is very high in carbohydrate and is therefore a very good energy food. The enlarged starch-filled roots contain nearly the maximum theoretical concentration of starch on a dry weight basis among food crops. Fresh roots contain 30% starch and very little protein. To get a balanced diet, it should be eaten with other foods with high protein content and various vitamins and minerals. In areas where cassava is a staple food, it could be over-eaten and insufficient amounts of other foods added to it because of poverty. The main reason for this may be the relative cheapness of cassava compared to other foods and relative ease of preparation and its ability to quickly replenish lost energy. Added to these is the fact of poverty which makes other relatively more expensive food items unavailable to the poor.
Where the poor live in river-rine areas or hunt games; meats and fish add necessary proteins else they purchase as much of these as they can to eat with their cassava. When cassava is eaten twice or thrice a day without adequate complements of other foods, there is likelihood of nutritional deficiency. The view that the food is the food for the poor comes from the fact that the very poor may lack purchasing power for alternative and more nutritious food. However, climbing the economic ladder may not necessarily significantly affect its consumption by those who have grown to love it.
As a food eaten by over fifty million people in Nigeria alone, it would seem a good base for nutritional supplements. Already some fortified varieties exist and are distributed by the IITA (International Institute For Tropical Agriculture). For many of those who love it, a form of it is a must-eat every day. Young tender leaves of cassava are used as potherb in some cultures. These leaves contain 8-10% of protein. One clone of cassava with variegated leaves is planted as ornamental. Cassava is the major source of low cost carbohydrate for populations in humid tropics.
Toxicities: All parts of the plant have glucosides with the leaves having the highest concentrations. In the roots, the peel has higher concentration than the interior. Sweet cassava has about 20mg of hydro-cyanide (HCN) per kilogram of fresh roots while bitter cassava has about 50 times as much. Under–processed roots of high HCN cultivars may result in health problems. Literatures on production figures in countries differ in rating. Nigeria is presently adjured the highest producer followed by Thailand. While Nigeria produces the highest amount, it does so with the lowest productivity because of production technology. While Nigeria production is mostly used as food, Thailand production goes mainly for feed. Other high producers are Brazil and Zaire. Thailand is the main exporter to Europe.
Removing the leaves 2 weeks before harvest lengthens the shelf life of the root from a few days to 2 weeks. Dipping the roots in paraffin or wax or storing in plastic bags reduces the incidence of vascular streaking and extends shelf life to 3-4 weeks. Roots can be peeled and frozen. Traditionally, roots are packed in moist mulch to extend shelf life.
Apart from processing the crop for direct consumption as Gari, Fufu, Tapioca, manioc, cassava is used in many other ways. Dried roots can be milled into flour. Maize may be added during the milling process to add protein. The flour can be used for baking bread. It may be used as partial substitute to wheat flour. Bread wholly made from cassava is being marketed in the USA for people with alleges to wheat flour. Fresh roots of sweet cassava can be sliced thinly and deep fried as chips. Roots can be peeled, grated and washed in water to extract starch, which can be used to make bread crackers, pasta and peals of tapioca. Unpeeled roots can be grated and dried for use as animal feed. The leaves can add protein to animal feed.
Industrial uses: Cassava is used in the manufacture of papers, textiles, adhesives, high fructose syrup and alcohol.The government of Nigeria has taken cassava as a major crop for food security and exports. With relative ease of cultivation, cassava may as well become the carbohydrate crop to look up to in Africa’s quest for food security. Some already call it Africa’s food security crop.
The Federal Ministry of Agriculture is promoting the use of cassava to supplement wheat in bread. The government has recommended at least 20% cassava content. Nigeria is the largest producer of cassava in the world. This directive or advice from government is to help increase utilization of cassava within the country and also save some of the money expended on importation of wheat. Some people have raised the issue of nutritional adequacy, value of protein in cassava being lower. Question is, why do people eat bread? Most of the bread eaten is eaten in cities where it takes time to prepare other foods especially in the morning. Bread is handy; it can easily be packed and taken to work or school. It is not messy.
It can be preserved for days and it does not need any further processing before eating. This greatly meets the needs of fast foods for workers outside home and especially city dwellers. Therefore one considers cassava supplementation as good for the country. Bread is already being fortified with vitamins and this will still be done in cassava bread. If the cassava bread becomes cheaper than the 100% wheat bread and its demand increases, we create higher demand for cassava. Just as is done
in 100% with bread, cassava bread can be eaten with other protein rich foods.