Manihot esculenta, cassava, is a perennial woody shrub in the Euphorbiaceae (spurge family) native to South America but now grown in tropical and sub-tropical areas worldwide for the edible starchy roots (tubers), which are an major food source in the developing world, in equatorial regions including Africa, South America, and Oceania. Also known as yuca (although not related to the genus Yucca), manioc, and tapioca, the dried root is the source of tapioca (used in the U.S. to make pudding).
The cassava shrub may grow to 2.75 meters (9 feet) tall, with leaves deeply divided into 3–7 lobes. The shrub is often grown as an annual, and propagated from stem cuttings after tubers have been harvested. The fruit is small, roughly 1 cm (1/2 inch) in diameter, but root tubers in cultivated varieties (which require 9–18 months to grow to harvestable size) can be 5–10 cm in diameter and 15–30 cm long. Fresh roots and leaves contain cyanide compounds including linamarin (cyanogenic glucoside) and hydrocyanic acid at levels that may be toxic, but properly treated (in a labor-intensive process that may include roasting, soaking, or fermentation, as shown in this YouTube clip, An Introduction to Cassava), the cyanide content is neglible. “Bitter” varieties contain more of these compounds than “sweet” varieties—although flavor is an imperfect indicator—but are often preferred by farmers for their pest-repellent properties.
Cassava, which may be the most widely grown root crop in the world, originated in western and southern Mexico and tropical South America (likely Brazil). Archaeological evidence suggests that it was cultivated in Peru 4,000 years ago, and in Mexico by 2,000 years ago. It was introduced to West Africa in the 16th century, and became a major food crop there and in Asia. Total 2010 global production was 228 million metric tons, harvested from 18.4 million hectares, with Nigeria, Thailand, and Brazil producing the largest amounts. In optimal conditions, cassava may yield up to 68 tons per hectare in a year, but typical yields are 10 tons/hectare. In addition, cassava is often intercropped with maize, vegetables, legumes, cocoa, and coffee.
Cassava tubers are prepared in various forms as a food (see ”culinary uses” in detailed entry), and are an important source of carbohydrates; they also contain significant amounts of phosphorus and iron, and are relatively rich in vitamin C. The leaves, which must also be treated to remove cyanide compounds before eating, contain 20–30% protein and are used as vegetable. Cassava is also used as a livestock feed in Latin America, the Caribbean, and Europe, and is increasingly cultivated for use as a biofuel (in China, for example).
(Bailey 1976, FAOSTAT 2012, Sadik 1988, Wikipedia 2011)
Derivation of specific name
Milkweed Family (Euphorbiaceae). Cassava is a tall semi-woody perennial shrub or tree, up to 7 m high, dbh up to 20 cm, single to few stems, sparingly branching; branchlets light green to tinged reddish, nodes reddish. The outer bark is smooth, light brown to yellowish grey; inner bark cream-green; exudate thin, watery; wood soft, creamy straw. The leaves: petiole light greenish to red; blade basally attached or slightly (up to 2 mm) peltate, dark green above, pale light greenish grayish underneath, sometimes variegated; lobes narrow, 2.9-12.5 times as long as wide; central unlobed part usually short, lobes 15-21 times as long. Inflorescences lax, with 3-5 together in fascicles; pedicels light green to red. Staminate flowers: calyx divided to halfway or more, green to white to lobes white to reddish with white median band inside to red purple, glabrous except for apex of calyx tube and inner side of segments finely hairy; filaments white, anthers yellow; disc yellow to light orange. Pistillate flowers: calyx green with red margin and midrib, hairy along the margin and on the midrib inside; disc pink; ovary with 6 longitudinal ridges, green (with pinkish stripes) to orange; pistil and stigmas white. Fruit subglobose, green (to light yellow, white, dark brown), rather smooth, with 6 longitudinal wings. Seeds up to 12 mm long.
The tuberous edible root, grows in clusters of 4-8 at the stem base. Roots are from 1-4 inches in diameter and 8-15 inches long, although roots up to 3 feet long have been found. The pure white interior is firmer than potatoes and contains high starch content. The roots are covered with a thin reddish brown fibrous bark that is removed by scraping and peeling. The bark is reported to contain toxic hydrocyanic (prussic) acid, which must be removed by washing, scraping and heating
In general, the crop requires a warm humid climate. Temperature is important, as all growth stops at about 10ºC. Typically, the crop is grown in areas that are frost free the year round. The highest root production can be expected in the tropical lowlands, below 150 m altitude, where temperatures average 25-27°C, but some varieties grow at altitudes of up to 1 500 m.
The plant produces best when rainfall is fairly abundant, but it can be grown where annual rainfall is as low as 500 mm or where it is as high as 5,000 mm. The plant can stand prolonged periods of drought in which most other food crops would perish. This makes it valuable in regions where annual rainfall is low or where seasonal distribution is irregular. In tropical climates the dry season has about the same effect on Cassava as low temperature has on deciduous perennials in other parts of the world. The period of dormancy lasts two to three months and growth resumes when the rains begin again.
Cassava is drought resistant and grows well in poor soil. It is one of the most efficient producers of carbohydrates and energy among all the food crops.
Distribution: Cassava can be found from the United States to Africa, Asia, Europe, and the South Pacific. For current distribution, please consult the Plant profile page for this species on the PLANTS Web site.
Cassada, manioc, yuca, tapioca, mandioca, shushu, muk shue, cassave, maniok, tapioka, imanoka, tapioca, maniba, kasaba, katela boodin, manioc, manihot, yucca, mandioca, sweet potato tree, Brazilian arrowroot, and tapioca plant.
Regularity: Regularly occurring
Native of Brazil; now common throughout the tropics
State - Kerala, District/s: All Districts"
Habitat & Distribution
Cassava is a tropical root crop, requiring at least 8 months of warm weather to produce a crop. However, under adverse conditions such as cool or dry weather it can take 18 or more months to produce a crop. Cassava is traditionally grown in a savanna climate, but can be grown in extremes of rainfall; however, it does not tolerate flooding. In droughty areas it looses its leaves to conserve moisture, producing new leaves when rains resume. Cassava does not tolerate freezing conditions, but does tolerate a wide range of soil pH 4.0 to 8.0 and is most productive in full sun.
Propagation by seed: For agricultural purposes, cassava is propagated exclusively from cuttings because seed germination is usually less than 50 percent. Seedlings are raised from seed only for the purpose of selecting seedlings with fewer and smaller roots than those of the parents. Botanically seeds are used only for breeding purposes.
Propagation by cuttings: Propagate cassava by planting segments of the stem. Cut stems into 9-30 cm lengths; be sure to include at least one node. Segments can be buried vertically with 8-15 cm in the ground. The selection of healthy, pest-free cuttings is essential. Stem cuttings are sometimes referred to as 'stakes'. In areas where freezing temperatures are possible, plant cuttings as soon as the danger of frost has past. Cuttings can be planted by hand or by planting machines. Hand planting is done in one of three ways: vertical, flat below the soil surface or tilted. Under low rainfall conditions, vertical planting may result in the desiccation of the cuttings, while in areas of higher rainfall; flat-planted cuttings may rot. In general, flat planting 5-10 cm below the soil surface is recommended in dry climates and when mechanical planting is used. Germination seems to be higher; tubers tend to originate from a great number of points and grow closer to the surface of the soil, making better use of fertilizers applied on the surface and also making harvesting easier.
Vertical planting is used in rainy areas and tilted planting in semi-rainy areas. Observing the polarity of the cutting is essential in successful establishment of the planting. The top of the cutting must be placed upright. Typical plant spacing is 1m by 1m. Cuttings produce roots within a few days and new shoots soon appear at old leaf petiole axes on the stem. Early growth is relatively slow, thus weeds must be controlled during the first few months. Although cassava can produce a crop with minimal inputs, optimal yields are recorded from fields with average soil fertility levels for food crop production and regular moisture availability.
Responses to macro-nutrients vary, with cassava responding most to P and K fertilization. Vesicular-arbuscular mycorrhizae benefit cassava by scavenging for phosphorus and supplying it to the roots. High N fertilization, more than 100 kg of actual N/ha, may result in excessive foliage production at the expense of storage root development. Fertilizer should only be applied during the first few months of growth.
In moist soil, sprouting takes place within the first week after planting. Within a month of the beginning of planting, the substitution of new cuttings to replace those that did not sprout is still possible. Cassava is grown mainly as a cash crop and farmers may for ten years or more grow cassava on the same land. However, if the price of cassava roots drops, the farmers may shift to another crop (e.g., sugarcane, maize or sorghum) until cassava again becomes the more profitable crop.
Life History and Behavior
Molecular Biology and Genetics
Hydrocyanic acid is liberated upon hydrolysis of linamarine and lautostraline, two cyanogenetic heterosides in the starchy root. Compounds in plant exhibit antibacterial, antiviral and antifungal activity.
Statistics of barcoding coverage: Manihot esculenta
Public Records: 0
Specimens with Barcodes: 7
Species With Barcodes: 1
National NatureServe Conservation Status
Rounded National Status Rank: NNA - Not Applicable
NatureServe Conservation Status
Rounded Global Status Rank: GNR - Not Yet Ranked
Reasons: Manihot esculenta is cultivated in all tropical countries of the world. However, the species is not known to occur in a purely wild state. EGR data supports GRANK of G?
Please consult the PLANTS Web site and your State Department of Natural Resources for this plant’s current status (e.g. threatened or endangered species, state noxious status, and wetland indicator values).
Pests and potential problems
Virus diseases. Mosaic, the brown streak and leaf curl of tobacco may attack leaves, stems and branches. Many parts of Africa harbor these diseases and attempts are being made to select resistant varieties.
Bacterial disease. Bacteria such as Phytomonas manihotis (in Brazil), Bacterium cassava (in Africa) and Bacterium solanacearum (in Indonesia) may attack roots, stems or leaves of cassava plants.
Mycoses. There are kinds which attack roots, stems, or leaves of cassava plants and cause various diseases.
Insects. Some insects affect the plant directly (locusts, beetles and ants); others affect the plant indirectly by the transfer of virus (aphids).
Animals. Rats, goats and wild pigs are probably the most troublesome; they feed on the roots, especially in areas adjacent to forests
Insects, diseases and other pest: In many regions, the cassava plant is not normally affected by diseases or pests. However, in others it may be attacked by the following:
Cultivars, improved and selected materials (and area of origin)
Contact your local Natural Resources Conservation Service (formerly Soil Conservation Service) office for more information. Look in the phone book under ”United States Government.” The Natural Resources Conservation Service will be listed under the subheading “Department of Agriculture.”
The hoe remains the principal implement for cultivating, weeding and harvesting.
Plowing and harrowing, are usually done by tractor.
A mechanical two row planter using a tractor driver and two men on the machine to feed cuttings from the reserve bins into the rotating planting turntable. In operation, the cuttings fall in succession through a hole into a furrow opened by a simple furrower. A pair of disks throws dirt into the furrow and floats pulled by chains pack the soil over the cuttings. The planter is able to cover about 5 hectares per day.
A gasoline-powered table saw is used to prepare the cuttings for planting. The machine has the advantage of speed and regularity of produced cuttings.
A topping machine consisting of a heavy screen mounted on the front of a tractor has been developed to push down the tops: then a rotary mower on the back of the same tractor can cut the downed top to make harvesting by hand possible. The height at which the tops are cut back can be easily regulated with any rotary mower.
Cassava is not a crop that lends itself readily to mechanical harvesting because of the way the tubers grow. They may spread over 1 m and penetrate 50 60 cm. Careless use of machinery for harvesting can damage tubers, resulting in a darkening due to oxidation that will lower the value of the flour. The mould-board plow has been used to make hand harvesting less tedious. Stalks can be cut successfully by a mid-mounted mower or a topping machine, and the roots are lifted mechanically with a mid-mounted disk terrace.
General: Cassava is either planted as a single crop or intercropped with maize, legumes, vegetables, rubber, oil palm or other economic important plants. Mixed planting reduces the danger of loss caused by unfavorable weather and pests by spreading the risk over plants with different susceptibilities.
Cassava grows best on light sandy loams or on loamy sands which are moist, fertile and deep. It grows well on soils ranging in texture from the sands to the clays and on soils of relatively low fertility. Cassava can produce an economic crop on soils so depleted by repeated cultivation that they have become unsuitable for other crops. On very rich soils the plant may produce stems and leaves at the expense of roots. Cassava will grow on a wide range of soils, provided the soil texture is friable enough to allow the development of the tubers.
When cassava is grown as the first crop in forest land no further preparation is required than the clearing of the forest growth. When cassava is grown after other crops it often can be planted without further preparation of the soil, once the preceding crop has been harvested or the soil has been plowed two or three times until free from grass and other plants.
No fertilization is required when the land is freshly cleared or when there is enough land to enable growers to substitute new land for old when yields fall. Like all rapidly growing plants yielding carbohydrates, cassava has high nutrient requirements and exhausts the soil very rapidly. When cassava is grown on the land for a number of years in succession or in rotation the soil nutrients are reduced and must therefore be returned to the soil by fertilization. Large commercial farmers replace the nutrients lost by applying artificial fertilizers that are usually too costly for the small farmer. Small farmers replace the nutrient loss by using different kinds of organic manures, such as cattle or duck manure or garbage to replace the nutrients taken from the soil.
Cassava is frequently cultivated as a temporary shade plant in young plantations of cocoa, coffee, rubber or oil palm. When cultivated as a temporary shade plant, no special attention is given to the cassava plant. When grown alone, the plants require little maintenance after planting. Irrigation may be required if there is no rain, and hoeing of the earth helps preserve the subsoil humidity, especially in dry sandy soils. The chief problem is weed control which may be desirable to weed the crop two or three times until the plants are well developed and their shade prevents the growth of weeds.
Maturity differs from one variety to another, but for food the tubers can be harvested at almost any age below 12 months. From the standpoint of maximum starch production, the optimum age for harvest is 18-20 months. During this growth period both root and starch production increase rapidly to their maximum value, after which root production decreases slowly and starch production much more rapidly on account of the declining starch content of the tubers.
If the roots are left in the ground, starch content increases with age until, at a certain point; lignifications takes place, causing the roots to become tough and woody, so that they are harder to prepare for consumption and other uses.
Harvesting of cassava can be done throughout the year when the roots reach maturity. In regions with seasonal rains, harvesting is usually done in the dry season, during the dormant period of the plant; where rain prevails all year round, cassava is harvested throughout the year.
There is no mature stage for cassava; because plants are ready for harvest as soon as there are storage roots large enough to meet the requirements of the consumer. Under the most favorable conditions, yields of fresh roots can reach 90 t/ha while average world yields from mostly subsistence agricultural systems average 10 t/ha. Typically harvesting can begin as soon as eight months after planting. In the tropics, plants can remain un-harvested for more than one growing season, allowing the storage roots to enlarge further. However, as the roots age and enlarge, the central portion becomes woody and inedible.
Harvesting is still generally a manual operation, although equipment to facilitate this operation is being considered. The day before harvest, the plants are "topped" the stalks are cut off 40-60 cm above ground by hand, machete or machine and piled at the side of the field. This length of stalk is left as a handle for pulling. Material required for the next planting is selected and the rest is burned. In light soils the roots are slowly drawn from the soil simply by pulling the stems or with the help of a kind of crowbar and the tubers are cut off the stock. In heavier soils a hoe may be required to dig up the roots before the plant is pulled out. It must be noted that once the plants have been topped, lifting of the roots must not be delayed, as sprouting and a drastic fall in the starch content of the tubers will result.
Once the roots are harvested, they begin to deteriorate within about 48 hours, initially owing to enzymatic changes in the roots and then to rot and decay. The roots may be kept refrigerated for up to a week or stored in the ground for longer periods if they are not detached from the plant.
In most of the tropical world cassava is grown on small plots; however, in some countries (e.g., Mexico, Brazil, and Nigeria) large plantations have been established. The degree of mechanization depends on the amount of land, available labor in the area and general policy regarding the use of manual labor.
The use of machinery for land preparation is preferable to manual labor to ensure the best possible seed bed for tuber development. Subsequent operations of planting, weeding, topping and harvesting can be done by hand as well as by machinery.
The following is an outline of the present use of machinery in cassava cultivation:
Relevance to Humans and Ecosystems
Root: Root-starch applied in a plaster soaked with Carapa oil onto shattered muscles. Root-starch mixed with rum and rubbed onto children for abscesses, skin eruptions; in ointment for the fungal dermatitis "tete" in Guyana; grated for cuts. Juice is mildly diuretic. Sugar cane and annatto are employed in an antidote to ingested water which has been poisoned by the soaking roots of this plant. Root: Used for abcesses, sores and “evil spirits” in NW Guyana. Leaf: Hemostatic plaster for skin wounds.
Food products: There are hydrocyanic glucosides (HCN) in all parts of the plant that are poisonous. These glucosides are removed by peeling the roots and boiling in water.
Cassava is one of the leading food and feed plants of the world. It ranks fourth among staple crops, with a global production of about 160 million tons per year. Most of this is grown in three regions: West Africa and the adjoining Congo basin, tropical South America and south and Southeast Asia. The young tender leaves are used as a potherb, containing high levels of protein and vitamins C and A. The leaves are prepared in a similar manner as spinach, while eliminating toxic compounds during the cooking process.
It is mainly used for human consumption, less for animal consumption and for industrial purposes, though this may vary by country. The roots are rarely eaten fresh but are usually cooked, steamed, fried or roasted when fresh or after drying or fermenting. It is advisable to peel, boil, grind or cut, and dry the roots in order to diminish the contents of cyanogenic glucosides. All plant parts contain cyanogenic glucosides with the leaves having the highest concentrations. In the roots, the peel has a higher concentration than the interior. In the past, cassava was categorized as either sweet or bitter, signifying the absence or presence of toxic levels of cyanogenic glucosides. Sweet cultivars can produce as little as 20 mg of HCN per kg of fresh roots, while bitter ones may produce more than 50 times as much. The bitterness is identified through taste and smell. This is not a totally valid system, since sweetness is not absolutely correlated with HCN producing ability. In cases of human malnutrition, where the diet lacks protein and iodine, under processed roots of high HCN cultivars may result in serious health problems.
Cassava provides a major source of calories for poor families, because of its high starch content. With minimum maintenance, the farmers can dig up the starchy root of the cassava and eat it 6 months to 3 years after planting. In Africa, people also eat the leaves of the cassava as a green vegetable, which provide a cheap and rich source of protein and vitamins A and B. In Southeast Asia and Latin America, cassava has also taken on an economic role. Various industries use it as a binding agent, because it is an inexpensive source of starch.
Cassava flour is used to make cookies, quick breads, loaf breads, pancakes, doughnuts, dumplings, muffins, bagels. Cassava extracted juice is fermented into a strong liquor called kasiri. The peeled roots of the sweet variety are usually eaten cooked or baked.
The juice can be concentrated and sweetened until it becomes a dark viscous syrup called kasripo (casareep). This syrup has antiseptic properties and is used for flavoring.
Livestock: Cassava leaves and stem meal are used for feeding dairy cattle. Both fresh and dried cassava roots are consumed by ruminants in different forms (chopped, sliced, or ground). Cassava bushes three to four months old are harvested as forage for cattle and other ruminants.
Ornamental: One clone with variegated leaves is known to be planted as an ornamental.
Commercial: Cassava starch is used in the production of paper, textiles, and as monosodium glutamate (MSG), an important flavoring agent in Asian cooking. In Africa, cassava is used as partial substitution for wheat flour.
Ethnobotanic: In Samoa, cassava was used to induce abortion. The Amerindians use the brown juice, obtained during processing, for burns.
The root of the bitter variety is very poisonous when raw. Cooking destroys the hydrocyanic acid; the cooking water must be discarded.
Manihot esculenta, with common names cassava (//), Brazilian arrowroot, manioc, and tapioca, a woody shrub of the Euphorbiaceae (spurge) family native to South America, is extensively cultivated as an annual crop in tropical and subtropical regions for its edible starchy tuberous root, a major source of carbohydrates. Though it is sometimes called yuca in Spanish, it differs from the yucca, an unrelated fruit-bearing shrub in the Asparagaceae family. Cassava, when dried to a powdery (or pearly) extract, is called tapioca; its fermented, flaky version is named garri.
Cassava is the third largest source of food carbohydrates in the tropics, after rice and maize. Cassava is a major staple food in the developing world, providing a basic diet for over half a billion people. It is one of the most drought-tolerant crops, capable of growing on marginal soils. Nigeria is the world's largest producer of cassava, while Thailand is the largest exporter of dried cassava.
Cassava is classified as sweet or bitter. Farmers often prefer the bitter varieties because they deter pests, animals, and thieves. Like other roots and tubers, both bitter and sweet varieties of cassava contain antinutritional factors and toxins. 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. The more toxic varieties of cassava are a fall-back resource (a "food security crop") in times of famine in some places.
- 1 Description
- 2 Vernacular names
- 3 History
- 4 Economic importance
- 5 Uses
- 6 Food use processing and toxicity
- 7 Farming
- 8 See also
- 9 References
- 10 External links
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 (2.0 to 3.9 in) in diameter at the top, and around 15 to 30 cm (5.9 to 11.8 in) 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.
In the vernacular languages of the places where it is cultivated, cassava is called yuca (Spanish), mandi'o (Guaraní), mandioca (Spanish and Portuguese), aipim or macaxeira (Portuguese), manioka or maniota (Polynesian), balinghoy or kamoteng kahoy (in the Philippines), শিমলু আলু or "shimolu aalu" (Assamese), tabolchu (Garo), kuchik kilangu or maravallik kilangu (Tamil), akpụ (Igbo), rōgṑ (Hausa), mogo (throughout Africa), and kappa (predominantly in India).
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 more than 10,000 years BP. Forms of the modern domesticated species can also be found growing in the wild in the south of Brazil. By 4,600 BC, manioc pollen appears in the Gulf of Mexico lowlands, at the San Andrés archaeological site. The oldest direct evidence of cassava cultivation comes from a 1,400-year-old Maya site, Joya de Cerén, in El Salvador. 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. Its cultivation was continued by the colonial Portuguese and Spanish.
Cassava was introduced to Africa by Portuguese traders from Brazil in the 16th century. Maize and cassava are now important staple foods, replacing native African crops. Cassava is sometimes described as the 'bread of the tropics' but should not be confused with the tropical and equatorial bread tree (Encephalartos), the breadfruit (Artocarpus altilis) or the African breadfruit (Treculia africana).
World production of cassava root was estimated to be 184 million tonnes in 2002, rising to 230 million tonnes in 2008. The majority of production in 2002 was 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 Caribbean. Nigeria 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%). Worldwide cassava production increased by 12.5% between 1988 and 1990.
In 2010, the average yield of cassava crops worldwide was 12.5 tonnes per hectare. The most productive cassava farms in the world were in India, with a nationwide average yield of 34.8 tonnes per hectare in 2010.
Cassava, yams (Dioscorea spp.) and sweet potatoes (Ipomoea batatas) are important sources of food in the tropics. The cassava plant gives the third highest yield of carbohydrates per cultivated area among crop plants, after sugarcane and sugar beets. Cassava plays a particularly important role in agriculture in developing countries, 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 offers flexibility to resource-poor farmers because it serves as either a subsistence or a cash crop.
No continent depends as much on root and tuber crops in feeding its population as does Africa. In the humid and subhumid areas of tropical Africa, it is either a primary staple food or a secondary costaple. In Ghana, for example, cassava and yams occupy an important position the agricultural economy and contribute about 46% of the agricultural gross domestic product. Cassava accounts for a daily caloric 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, agbeli, meaning "there is life". 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.
In Tamil Nadu, India, the National Highway 68 between Thalaivasal and Attur has many cassava processing factories alongside it—indicating a local abundance. Cassava is widely cultivated and eaten as a staple food in Andhra Pradesh and in Kerala besides being commonly cultivated and popular in Assam where it plays an important source of carbohydrates specially for natives of hilly areas.
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 Vietnam and Thailand. Over 60% of cassava production in China is concentrated in a single province, Guangxi, averaging over 7 million tonnes annually.
Alcoholic beverages made from cassava include Cauim and tiquira (Brazil), kasiri (Sub-Saharan Africa), Impala (Mozambique) masato (Peruvian Amazonia chicha), parakari or kari (Guyana), nihamanchi (South America) aka nijimanche (Ecuador and Peru), ö döi (chicha de yuca, Ngäbe-Bugle, Panama), sakurá (Brazil, Surinam).
Cassava can be cooked in many ways. The soft-boiled root of the sweet variety 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. This plant is used in cholent in some households, as well. Deep fried (after boiling or steaming), it can replace fried potatoes, bringing a distinctive flavor. It can be made into a flour that is used in breads, cakes and cookies. In Brazil, detoxified manioc is ground and cooked to a dry, often hard or crunchy meal known as farinha which is used as a condiment, toasted in butter, or eaten alone as a side dish.
Cassava root is essentially a carbohydrate source. 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 2,000 m (6,600 ft) above sea level, in equatorial temperatures, with rainfalls of 50 millimeters to 5 m (16 ft) 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, release hydrocyanic 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, bitter cassava must be treated and prepared properly prior to human or animal consumption, while sweet cassava can be used after simple boiling.
Comparison with other major staple foods
The following table shows the nutrient content of cassava and compares it with major staple foods in a raw form. Raw forms of these staples, however, are not edible and cannot be digested. These must be sprouted, or prepared and cooked as appropriate for human consumption. In sprouted or cooked form, the relative nutritional and antinutritional contents of each of these grains is remarkably different from that of raw form of these grains reported in this table. The nutrition value for each staple food in cooked form depends on the cooking method (boiling, baking, steaming, frying, etc.).
The table shows that cassava is a good energy source, but like potato, cassava's protein and essential nutrients density is lower than other staple foods.
|STAPLE:||Maize / Corn[A]||Rice (white)[B]||Rice (brown)[I]||Wheat[C]||Potato[D]||Cassava[E]||Soybean (Green)[F]||Sweet potato[G]||Sorghum[H]||Yam[Y]||Plantain[Z]|
|Component (per 100g portion)||Amount||Amount||Amount||Amount||Amount||Amount||Amount||Amount||Amount||Amount||Amount|
|Vitamin C (mg)||0||0||0||0||19.7||20.6||29||2.4||0||17.1||18.4|
|Pantothenic acid (mg)||0.42||1.01||1.49||0.95||0.30||0.11||0.15||0.80||-||0.31||0.26|
|Vitamin B6 (mg)||0.62||0.16||0.51||0.3||0.30||0.09||0.07||0.21||-||0.29||0.30|
|Folate Total (μg)||19||8||20||38||16||27||165||11||0||23||22|
|Vitamin A (IU)||214||0||0||9||2||13||180||14187||0||138||1127|
|Vitamin E, alpha-tocopherol (mg)||0.49||0.11||0.59||1.01||0.01||0.19||0||0.26||0||0.39||0.14|
|Vitamin K1 (μg)||0.3||0.1||1.9||1.9||1.9||1.9||0||1.8||0||2.6||0.7|
|Saturated fatty acids (g)||0.67||0.18||0.58||0.26||0.03||0.07||0.79||0.02||0.46||0.04||0.14|
|Monounsaturated fatty acids (g)||1.25||0.21||1.05||0.2||0.00||0.08||1.28||0.00||0.99||0.01||0.03|
|Polyunsaturated fatty acids (g)||2.16||0.18||1.04||0.63||0.04||0.05||3.20||0.01||1.37||0.08||0.07|
|A corn, yellow||B rice, white, long-grain, regular, raw, unenriched|
|C wheat, hard red winter||D potato, flesh and skin, raw|
|E cassava, raw||F soybeans, green, raw|
|G sweet potato, raw, unprepared||H sorghum, raw|
|Y yam, raw||Z plantains, raw|
|I rice, brown, long-grain, raw|
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 Eleventh Five-Year Plan in the People's Republic of China, the target is to increase the application of ethanol fuel by nongrain feedstock to 2 million tonnes, and that of biodiesel 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 Beihai, with annual output of 200 thousand tons, which would need an average of 1.5 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 US gallons (120,000 m3) a year of bioethanol from cassava plants.
Cassava tubers and hay are used worldwide as animal feed. Cassava hay is harvested at a young growth stage (three to four months) when it reaches about 30 to 45 cm (12 to 18 in) above ground; it is then sun-dried for one to two days until it has final dry matter content of less than 85%. Cassava hay contains high protein (20–27% crude protein) and condensed tannins (1.5–4% CP). It is valued as a good roughage source for ruminants such as dairy or beef cattle, buffalo, goats, and sheep, whether by direct feeding or as a protein source in concentrate mixtures.
Manioc is also used in a number of commercially-available laundry products, especially as starch for shirts and other garments. Using manioc starch diluted in water and spraying it over fabrics before ironing helps stiffen collars.
Cassava root has been promoted as a treatment for bladder and prostate cancer. However, according to the American Cancer Society, "there is no convincing scientific evidence that cassava or tapioca is effective in preventing or treating cancer".
Food use processing and toxicity
Cassava roots,peels and leaves should not 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, respectively. 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 of 25 mg of pure cassava cyanogenic glucoside, which contains 2.5 mg of cyanide, is sufficient to kill a rat. Excess cyanide residue from improper preparation is known to cause acute cyanide intoxication, and goiters, and has been linked to ataxia (a neurological disorder affecting the ability to walk, also known as konzo). It has also been linked to tropical calcific pancreatitis in humans, leading to chronic pancreatitis.
Societies that traditionally eat cassava generally understand some processing (soaking, cooking, fermentation, etc.) is necessary to avoid getting sick.
Symptoms of acute cyanide intoxication appear four or more hours after ingesting raw or poorly processed cassava: vertigo, vomiting, and collapse. In some cases, death may result within one or two hours. It can be treated easily with an injection of thiosulfate (which makes sulfur available for the patient's body to detoxify by converting the poisonous cyanide into thiocyanate).
"Chronic, low-level cyanide exposure is associated with the development of goiter and with tropical ataxic neuropathy, a nerve-damaging disorder that renders a person unsteady and uncoordinated. Severe cyanide poisoning, particularly during famines, is associated with outbreaks of a debilitating, irreversible paralytic disorder called konzo and, in some cases, death. The incidence of konzo and tropical ataxic neuropathy can be as high as 3% in some areas."
Brief soaking (four hours) of cassava is not sufficient, but soaking for 18–24 hours can remove up to half the level of cyanide. Drying may not be sufficient, either.
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 flour 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 Caribbean. 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.
A safe processing method used by the pre-Columbian people of the Americas 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 83% 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.
The traditional method used in West Africa is to peel the roots and put them into water for three 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 goiters seen in the Akoko area of southwestern Nigeria.
A project called "BioCassava Plus" is developing a cassava with lower cyanogen glucosides and fortified with vitamin A, iron and protein to help the nutrition of people in sub-Saharan Africa. In 2011, the director of the program said he hoped to obtain regulatory approvals by 2017.
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 oxidized and blackened within two to three days after harvest, rendering it unpalatable and useless. Recent work has indicated that PPD is related to the accumulation of reactive oxygen species (ROS)initiated by cyanide release during mechanical harvesting. Based on this research, cassava shelf life was increased to up to 2 weeks by overexpressing a cyanide insensitive alternative oxidase
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. Hiranandan 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 postharvest 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 postharvest 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 postharvest losses of chips of about 14% after four months of storage, about 20% after seven months of storage and up to 30% when P. truncatus attacked the dried chips. In addition, Wright et al. (1993) estimated 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.
Plant breeding has resulted in cassava that is tolerant to PPD. Sánchez et al. identified four different sources of tolerance to PPD. One comes from Walker's Manihot (M. walkerae) of southern Texas in the United States and Tamaulipas in Mexico. A second source was induced by mutagenic levels of gamma rays, which putatively silenced one of the genes involved in PPD genesis. A third source was a group of high-carotene clones. The antioxidant properties of carotenoids are postulated to protect the roots from PPD (basically an oxidative process). Finally, tolerance was also observed in a waxy-starch (amylose-free) mutant. This tolerance to PPD was thought to be cosegregated with the starch mutation, and is not a pleiotropic effect of the latter.
In Africa, a previous issue of great significance was the cassava mealybug (Phenacoccus manihoti) and cassava green mite (Mononychellus tanajoa). These pests 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 Center for Africa of the IITA under the leadership of Dr. Hans Rudolf Herren. 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. An outbreak of the virus in Africa in the 1920s led to a major famine. 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 mi (80 km) per year, and as of 2005 may be found throughout Uganda, Rwanda, Burundi, the Democratic Republic of the Congo and the Republic of the Congo.
A wide range of plant parasitic nematodes have been reported associated with cassava worldwide. These include Pratylenchus brachyurus., Rotylenchulus reniformis, Helicotylenchus spp., Scutellonema spp. and Meloidogyne spp., of which Meloidogyne incognita and Meloidogyne javanica are the most widely reported and economically important. Meloidogyne spp. feeding produces physically damaging galls with eggs inside them. Galls later merge as the females grow and enlarge, and they interfere with water and nutrient supply. Cassava roots become tough with age and restrict the movement of the juveniles and the egg release. It is therefore possible that extensive galling can be observed even at low densities following infection. Other pest and diseases can gain entry through the physical damage caused by gall formation, leading to rots. They have not been shown to cause direct damage to the enlarged storage roots, but plants can have reduced height if there was loss of enlarged root weight.
Research on nematode pests of cassava is still in the early stages; results on the response of cassava is, therefore, not consistent, ranging from negligible to seriously damaging. Since nematodes have such a seemingly erratic distribution in cassava agricultural fields, it is not easy to clearly define the level of direct damage attributed to nematodes and thereafter quantify the success of a chosen management method.
The use of nematicides has been found to result in lower numbers of galls per feeder root compared to a control, coupled with a lower number of rots in the storage roots. The nematicide Femaniphos, when used, did not affect crop growth and yield parameter variables measured at harvest. Nematicide use in cassava is neither practical nor sustainable; currently the use of tolerant and resistant varieties is the most practical and sustainable management method.
- Attiéké – a side dish made from cassava that is a part of the cuisine of Côte d'Ivoire in Africa
- Maní (Amazonian legend)
- List of ineffective cancer treatments
- Yellow cassava
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FG Creole: manioc, manioc amer, manioc petit Louis. FG Palikur: kiniki. Guyana: bitter cassava, cassava, poison cassava, putagee-cassava, sebayu cassava. Surinam: bittere cassava, cassave. Surinam Sranan: bita-kasaba, kasaba. Surinam Javan: ketela poehoen.
Lanjouw lists 34 common names used in Surinam for this plant. Among the Djuka tribe of Surinam Bush Negroes studied by Counter and Evans, improperly processed cassava bread consumed over a long period of time is believed to lead to a high incidence of high-frequency hearing loss. Cassava contains a cyanogenic glycoside called laminarin, which causes a neuropathy of the nervous system, especially the auditory nerve. Cassava is the main carbohydrate staple of many Bush people.
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