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Cassava (Manihot esculenta; also called yuca or manioc) is a woody shrub of the Euphorbiaceae (spurge family) native to West Brazil that is extensively cultivated as an annual crop in tropical and subtropical regions for its edible starchy tuberous root, a major source of carbohydrates. The flour made of the roots is called farinha de mandioca, biju and tapioca.

Cassava is the third largest source of carbohydrates for human food in the world.

The name "cassava" is sometimes spelled cassaba or cassada.
   
"Mandioca or cassada is likewise cultivated in great quantity" (p. 25).

See it also in The Complete Work of Charles Darwin Online. In English language publications, the plant may be occasionally called by local names, such as mandioca, aipim, or macaxeira (Brazilmarker), kassav (Haitimarker), mandi´o (Paraguay), akpu or ugburu (Nigeriamarker), bankye(Twi-Speaking Ghanamarker), mogo or mihogo (Swahili-speaking Africa), kappa (Malayalam-speaking Indiamarker), maniok (Sri Lankamarker), singkong (Indonesiamarker), ubi kayu (Malaysiamarker), kamoteng kahoy or balanghoy (Philippinesmarker), mushu (China), củ sắn or khoai mì (Vietnammarker), simal tarul (Darjeeling, Sikkim), and manioke or manioca (Polynesia) .

Description

Unprocessed cassava root
The cassava root is long and tapered, with a firm homogeneous flesh encased in a detachable rind, about 1 mm thick, rough and brown on the outside. Commercial varieties can be 5 to 10 cm in diameter at the top, and 50 to 80 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 if supplemented with the amino acid methionine despite containing cyanide.

History



Wild populations of M. esculenta subspecies flabellifolia, shown to be the progenitor of domesticated cassava, are centered in west-central Brazil where it was likely first domesticated no more than 10,000 years BP. By 6,600 BC, manioc pollen appears in the Gulf of Mexicomarker lowlands, at the San Andres archaeological site. The oldest direct evidence of cassava cultivation comes from a 1,400 year old Maya site, Joya de Cerénmarker, in El Salvadormarker. although the species Manihot esculenta likely originated further south in Brazilmarker and Paraguaymarker. With its high food potential, it had become a staple food of the native populations of northern South America, southern Mesoamerica, and the Caribbean by the time of the Spanish conquest, and its cultivation was continued by the colonial Portuguese and Spanish. Forms of the modern domesticated species can be found growing in the wild in the south of Brazilmarker. While there are several wild Manihot species, all varieties of M. esculenta are cultigens.

Cassava was a staple food for pre-Columbian peoples in the Americas, and is often portrayed in indigenous art. The Moche people often depicted yuca in their ceramics.

Economic impact

Cassava output in 2005
World production of cassava root was estimated to be 184 million tonnes in 2002. The majority of production is in Africa where 99.1 million tonnes were grown. 51.5 million tonnes were grown in Asia and 33.2 million tonnes in Latin America and the Caribbeanmarker. Nigeriamarker is the world's largest producer of cassava. However, based on the statistics from the FAO of the United Nations, Thailand is the largest exporting country of dried cassava with a total of 77% of world export in 2005. The second largest exporting country is Vietnam, with 13.6%, followed by Indonesia (5.8%) and Costa Rica (2.1%). World-wide cassava production increased by 12.5% between 1988 and 1990.

Cassava, together with yams (Dioscorea sp.) and sweet potatoes (Ipomea batatas) are important sources of food in the tropics. The cassava plant gives the highest yield of food energy per cultivated area per day among crop plants, except possibly for sugarcane . Cassava plays a particularly important role in developing countries’ farming—especially in sub-Saharan Africa—because it does well on poor soils and with low rainfall, and because it is a perennial that can be harvested as required. Its wide harvesting window allows it to act as a famine reserve and is invaluable in managing labor schedules. It also offers flexibility to resource-poor farmers because it serves as either a subsistence or a cash crop .

At the same time that underground storage of cassava is advantageous for managing work schedules, it may also lead to reduced quality of the roots, sometimes leaving the roots unsuitable for many types of processing. In some areas farmers have come to increasingly rely on dried Cassava chips. A 1992 study (Nweke et al.) revealed that about 42% of harvested cassava roots in West and East Africa are processed into dried chips and flour.

Cassava in cultivation in Democratic Republic of Congo
No continent depends as much on root and tuber crops in feeding its population as does Africa. In the humid and sub-humid areas of tropical Africa, cassava is either a primary staple food or a secondary co-staple. In Ghanamarker, for example, Cassava and yams occupy an important position the agricultural economy and contribute about 46% of the agricultural Gross Domestic Product (GDP). Cassava accounts for a daily calorie intake of 30% in Ghana and is grown by nearly every farming family. The importance of cassava to many Africans is epitomised in the Ewe (a language spoken in Ghana, Togo and Benin) name for the plant, agble, meaning "there is life." However, the price of cassava has risen significantly in the last half decade and lower-income people have turned to other carbohydrate-rich foods such as rice and spaghetti.

In Tamil Nadumarker, one of the 28 states of India, the National Highway 68 between Thalaivasalmarker and Atturmarker has many cassava processing factories (local name Sago Factory) alongside it—indicating an abundance of it in the neighborhood. Cassava is widely cultivated and eaten as a staple food in Andhra Pradeshmarker and in Keralamarker.

In the subtropical region of southern China, cassava is the fifth largest crop in term of production, after rice, sweet potato, sugar cane, and maize. China is also the largest export market for cassava produced in Vietnammarker and Thailandmarker. Over 60% of cassava production in China is concentrated in a single province, Guangxi, averaging over seven million tons annually.

Uses

Human food

Cassava-based dishes are widely consumed wherever the plant is cultivated. Some of these dishes have regional, national, or ethnic importance. Cassava must be cooked properly to detoxify it before it is eaten.

Cassava heavy cake
Cassava can be cooked in various ways. The soft-boiled root has a delicate flavor and can replace boiled potatoes in many uses: as an accompaniment for meat dishes, or made into purées, dumplings, soups, stews, gravies, etc.. Deep fried (after boiling or steaming), it can replace fried potatoes, with a distinctive flavor. Tapioca and foufou are made from the starchy cassava root flour. Tapioca is an essentially flavourless starchy ingredient, or fecula, produced from treated and dried cassava (manioc) root and used in cooking. It is similar to sago and is commonly used to make a milky pudding similar to rice pudding. Cassava flour, also called tapioca flour or tapioca starch, can also replace wheat flour, and is so-used by some people with wheat allergies or coeliac disease. Boba tapioca pearls are made from cassava root. It is also used in cereals for which several tribes in South America have used it extensively. It is also used in making cassava cake, a popular pastry.

The juice of the bitter cassava, boiled to the consistence of thick syrup and flavored with spices, is called cassareep. It is used as a basis for various sauces and as a culinary flavoring, principally in tropical countries. It is exported chiefly from Guyanamarker.

Cassava is used in bubble drink in East Asia.

Frozen cassava leaves from the Philippines sold at a Los Angeles market
The leaves can be pounded to a fine chaff and cooked as a palaver sauce in Sierra Leonemarker, usually with palm oil but vegetable oil can also be used. Palaver sauces contain meat and fish as well. It is necessary to wash the leaf chaff several times to remove the bitterness.

In DR Congomarker the leaves are used in a stew called Pondu.

Cassava was also used to make alcoholic beverages. The English explorer and naturalist Charles Waterton reported in Wanderings in South America (1836) that the natives of Guyanamarker used cassava to make liquor, which they abandoned when rum became available. Hamilton Rice, in 1913, also remarked on liquor being made from cassava in the Brazilianmarker rainforest.

Biofuel

In many countries, significant research has begun to evaluate the use of cassava as an ethanol biofuel feedstock. Under the Development Plan for Renewable Energy in the 11th Five-Year Plan in China, the target is to increase the application of ethanol fuel by non-grain feedstock to 2 million tonnes, and that of bio-diesel to 200 thousand tonnes by 2010. This will be equivalent to a substitute of 10 million tonnes of petroleum. As a result, cassava (tapioca) chips have gradually become a major source for ethanol production. On December 22, 2007, the largest cassava ethanol fuel production facility was completed in Beihaimarker with annual output of two hundred thousand tons, which would need an average of one and half million tons of cassava. In November 2008, China-based Hainan Yedao Group reportedly invested $51.5m (£31.8m) in a new biofuel facility that is expected to produce 33 million gallons a year of bio-ethanol from cassava plants .

Animal feed

Cassava is used worldwide for animal feed as well. Cassava hay is produced at a young growth stage, 3–4 months, harvested about 30-45 cm above ground, and sun-dried for 1–2 days until it has final dry matter of at least 85%. The cassava hay contains high protein content (20-27% Crude Protein) and condensed tannins (1.5-4% CP). It is used as a good roughage source for dairy, beef, buffalo, goats, and sheep by either direct feeding or as a protein source in the concentrate mixtures. More details can be searched from Metha Wanapat, Asian-Australasian Journal of Animal Sciences.

Ethnomedicine

  • The bitter variety of Manihot root is used to treat diarrhea and malaria.
  • The leaves are used to treat hypertension, headache, and pain.
  • Cubans commonly use cassava to treat irritable bowel syndrome, the paste eaten in excess during treatment.
  • As cassava is a gluten-free natural starch, there have been increasing incidences of its appearance in Western cuisine as a wheat alternative for sufferers of coeliac disease.


Food use processing and toxicity

Cassava root, peeled.
Cassava roots and leaves cannot 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. 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. A dose 40 mg of pure cassava cyanogenic glucoside is sufficient to kill a cow.

Cassava bread
Societies which traditionally eat cassava generally understand that some processing (soaking, cooking, fermentation, etc.) is necessary to avoid getting sick. However, consumption of insufficiently processed bitter cassava may cause konzo (also called mantakassa), a paralytic neurological disease. A safe processing method, developed by J. Ospina, 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 5/6 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.

For some smaller-rooted "sweet" varieties, cooking is sufficient to eliminate all toxicity. The cyanide is carried away in the processing water and the amounts produced in domestic consumption are too small to have environmental impact. The larger-rooted "bitter" varieties used for production of lemons or starch must be processed to remove the cyanogenic glucosides. The large roots are peeled and then ground into flour, which is then soaked in water, squeezed dry several times, and toasted. The starch grains that float to the surface during the soaking process are also used in cooking. The flour is used throughout South America and the Caribbeanmarker. Industrial production of cassava flour, even at the cottage level, may generate enough cyanide and cyanogenic glycosides in the effluents to have a severe environmental impact.

The traditional method used in West Africa is to peel the roots and put them into water for 3 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.

The reliance on cassava as a food source and the resulting exposure to the goitrogenic effects of thiocyanate has been responsible for the endemic goitres seen in the Akoko area of southwestern Nigeria.

Historically, people economically forced to depend on cassava risk chronic poisoning diseases, such as tropical ataxic neuropathy (TAN), or such malnutrition diseases as kwashiorkor and endemic goitre.

Cassava farming

Harvesting

Cassava is harvested by hand by raising the lower part of the stem and pulling the roots out of the ground, then removing them from the base of the plant. The upper parts of the stems with the leaves are plucked off before harvest. Cassava is propagated by cutting the stem into sections of approximately 15 cm, these being planted prior to the wet season.

Postharvest handling and storage

Cassava undergoes postharvest physiological deterioration, or PPD, once the tubers are separated from the main plant. The tubers, when damaged, normally respond with a healing mechanism. However, the same mechanism, which involves coumaric acids, initiates about 15 minutes after damage, and fails to switch off in harvested tubers. It continues until the entire tuber is oxidised and blackened within two to three days after harvest, rendering it unpalatable and useless.

PPD is one of the main obstacles currently preventing farmers from exporting cassavas abroad and generating income. Cassava can be preserved in various ways such as coating in wax or freezing.

The major cause of losses during cassava chip storage is infestation by insects. A wide range of species that feed directly on the dried chips have been reported as the cause of weight loss in the stored produce. Some loss assessment studies and estimations on dried cassava chips have been carried out in different countries. Hirandan and Advani (1955) measured 12 - 14% post-harvest weight losses in India for chips stored for about five months. Killick (1966) estimated for Ghana that 19% of the harvest cassava roots are lost annually, and Nicol (1991) estimated a 15 - 20% loss of -dried chips stored for eight months. Pattinson (1968) estimated for Tanzania a 12% weight loss of cassava chips stored for five months, and Hodges et al. (1985) assessed during a field survey post-harvest losses of up to 19% after 3 months and up to 63% after four to five months due to the infestation of Prostephanus truncatus (Horn). In Togo, Stabrawa (1991) assessed post-harvest weight losses of 5% after one month of storage and 15% after three months of storage due to insect infestation, and Compton (1991) assessed weight losses of about 9% for each store in the survey area in Togo. Wright et al. (1993) assessed post-harvest losses of chips of about 14% after four months of storage, about 20% after seven month of storage and up to 30% when P. truncatus attacked the dried chips. In addition, Wright et al. (1993) estimated that about 4% of the total national cassava production in Togo is lost during the chip storage. This was about equivalent to 0.05% of the GNP in 1989.

Cassava pests

In Africa the cassava mealybug (Phenacoccus manihoti) and cassava green mite (Mononychellus tanajoa) can cause up to 80% crop loss, which is extremely detrimental to the production of subsistence farmers. These pests were rampant in the 1970s and 1980s but were brought under control following the establishment of the Biological Control Centre for Africa of the IITA. The Centre investigated biological control for cassava pests; two South American natural enemies Apoanagyrus lopezi (a parasitoid wasp) and Typhlodromalus aripo (a predatory mite) were found to effectively control the cassava mealybug and the cassava green mite respectively.

The cassava mosaic virus causes the leaves of the cassava plant to wither, limiting the growth of the root. The virus is spread by the whitefly and by the transplanting of diseased plants into new fields. Sometime in the late 1980s, a mutation occurred in Uganda that made the virus even more harmful, causing the complete loss of leaves. This mutated virus has been spreading at a rate of 50 miles per year, and as of 2005 may be found throughout Uganda, Rwandamarker, Burundimarker, the Democratic Republic of the Congomarker and the Republic of the Congomarker.

Notes

  1. First International Meeting on Cassava Breeding, Biotechnology and Ecology, “Cassava improvement to enhance livelihoods in sub-Saharan Africa and northeastern Brazil” Brasilia 11-15 November 2006, p102 [1]
  2. Olsen, Kenneth M.; Schaal, Barbara A. (1999) "Evidence on the football of cassava: Phylogeography of Manihot esculenta" in Proceedings of the National Academy of Sciences of the United States of America (PNAS), Vol. 96, Issue 10, p. 5587 & 5590.
  3. Pope, Kevin; Pohl, Mary E. D.; Jones, John G.; Lentz, David L.; von Nagy, Christopher; Vega, Francisco J.; Quitmyer Irvy R.; " Origin and Environmental Setting of Ancient Agriculture in the Lowlands of Mesoamerica", Science, 18 May 2001:Vol. 292. no. 5520, pp. 1370 - 1373.
  4. University of Colorado at Boulder, (2007) "CU-Boulder Archaeology Team Discovers First Ancient Manioc Fields In Americas", press release August 20, 2007, accessed August 29, 2007.
  5. Berrin, Katherine & Larco Museum. The Spirit of Ancient Peru:Treasures from the Museo Arqueológico Rafael Larco Herrera. New York: Thames and Hudson, 1997.
  6. Stone, Glenn D. 2002 Both Sides Now: Fallacies in the Genetic-Modification Wars, Implications for Developing Countries, and Anthropological Perspectives. Current Anthropology, 43(4):611-630
  7. Frederick Douglass Opie, Hog and Hominy: Soul Food from Africa to America, (Columbia University Press 2008), chapters 1-2.
  8. p. 146
  9. [2]
  10. [3]
  11. [4]
  12. M.P.Cereda, M.C.Y.Matos (1996): Linamarin - The toxic compound of cassava. Journal of Venomous Animals and Toxins, vol. 2 no. 1. Center of Tropical Roots, CERAT-UNESP, São Paulo State University, Botucatu (SP), Brazil. doi: 10.1590/S0104-79301996000100002


References

  • Amazon Amidos, the first cassava starch industry of the North of Brazil.





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