Cassava

Cassava (Manihot esculenta), also called manioc, yuca, balinghoy, mogo, mandioca, kamoteng kahoy, and manioc root, a woody shrub of theEuphorbiaceae (spurge family) native to South America, is extensively cultivated as an annual crop in tropical and subtropical regions for its ediblestarchy, tuberous root, a major source of carbohydrates. It differs from the similarly spelled yucca, an unrelated fruit-bearing shrub in the Asparagaceaefamily. Cassava, when dried to a starchy, powdery (or pearly) extract is called tapioca, while its fermented, flaky version is named garri.

Cassava is the third-largest source of food carbohydrates in the tropics.^[1][2] Cassava is a major staple food in the developing world, providing a basic diet for around 502 million people.^[3] It is one of the most drought-tolerant crops, capable of growing on marginal soils. Nigeria is the world's largest producer of cassava.

Cassava root is a good source of carbohydrates, but a poor source of protein. A predominantly cassava root diet can cause protein-energy malnutrition.^[4]

Cassava is classified as sweet or bitter. Like other roots and tubers, Cassava contains antinutritional factors and toxins.^[5] It must be properly prepared before consumption. Improper preparation of cassava can leave enough residual cyanide to cause acute cyanide intoxication and goiters, and may even cause ataxia or partial paralysis.^[6] Nevertheless, farmers often prefer the bitter varieties because they deter pests, animals, and thieves.^[7] The more-toxic varieties of cassava are a fall-back resource (a "food security crop") in times of famine in some places.^[8]

Description

Unprocessed cassava roots

The cassava root is long and tapered, with a firm, homogeneous flesh encased in a detachable rind, about 1mm thick, rough and brown on the outside. Commercial varieties can be 5 to 10 cm in diameter at the top, and around 15 cm to 30 cm long. A woody cordon runs along the root's axis. The flesh can be chalk-white or yellowish. Cassava roots are very rich in starch, and contain significant amounts of calcium (50 mg/100g), phosphorus (40 mg/100g) and vitamin C (25 mg/100g). However, they are poor in protein and other nutrients. In contrast, cassava leaves are a good source of protein (rich in lysine), but deficient in the amino acid methionine and possibly tryptophan.^[9]

Nutritional profile of cassava

Cassava root is essentially a carbohydrate source.^[22] Its composition shows 60–65 percent moisture, 20–31 percent carbohydrate, 1–2 percent crude protein and a comparatively low content of vitamins and minerals. However, the roots are rich in calcium and vitamin C and contain a nutritionally significant quantity of thiamine, riboflavin and nicotinic acid. Cassava starch contains 70 percent amylopectin and 20 percent amylose. Cooked cassava starch has a digestibility of over 75 percent.

Cassava root is a poor source of protein. Despite the very low quantity, the quality of cassava root protein is fairly good in terms of essential amino acids. Methionine, cysteine and cystine are, however, limiting amino acids in cassava root.

Cassava is attractive as nutrition source in certain ecosystems because cassava is one of the most drought-tolerant crops, can be successfully grown on marginal soils, and gives reasonable yields where many other crops do not grow well. Cassava is well adapted within latitudes 30° north and south of the equator, at elevations between sea level and 2000 meters above sea level, in equatorial temperatures, with rainfalls of 50 millimeters to five meters annually, and to poor soils with a pH ranging from acidic to alkaline. These conditions are common in certain parts of Africa and South America.

Cassava is a highly productive crop in terms of food calories produced per unit land area per unit of time, significantly higher than other staple crops. Cassava can produce food calories at rates exceeding 250,000 cal/hectare/day compared with 176,000 for rice, 110,000 for wheat, and 200,000 for maize (corn).

Cassava, like other foods, also has antinutritional and toxic factors. Of particular concern are the cyanogenic glucosides of cassava (linamarin and lotaustralin). These, on hydrolysis, releasehydrocyanic acid (HCN). The presence of cyanide in cassava is of concern for human and for animal consumption. The concentration of these antinutritional and unsafe glycosides varies considerably between varieties and also with climatic and cultural conditions. Selection of cassava species to be grown, therefore, is quite important. Once harvested, cassava must be treated and prepared properly prior to human or animal consumption.