Cassava

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Cassava
Manihot esculenta - Kohler-s Medizinal-Pflanzen-090.jpg
Leaves of the cassava plant
Manihot esculenta 001.jpg
A cassava tuber (waxed)
Scientific classification Red Pencil Icon.png
Kingdom: Plantae
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Malpighiales
Family: Euphorbiaceae
Genus: Manihot
Species:
M. esculenta
Binomial name
Manihot esculenta
Synonyms [1]
  • Janipha aipi(Pohl) J.Presl
  • Janipha manihot(L.) Kunth
  • Jatropha aipi(Pohl) Göpp.
  • Jatropha diffusa(Pohl) Steud.
  • Jatropha digitiformis(Pohl) Steud.
  • Jatropha dulcisJ.F.Gmel.
  • Jatropha flabellifolia(Pohl) Steud.
  • Jatropha loureiroi(Pohl) Steud.
  • Jatropha manihotL.
  • Jatropha mitisRottb.
  • Jatropha paniculataRuiz & Pav. ex Pax
  • Jatropha silvestrisVell.
  • Jatropha stipulataVell.
  • Mandioca aipi(Pohl) Link
  • Mandioca dulcis(J.F.Gmel.) D.Parodi
  • Mandioca utilissima(Pohl) Link
  • Manihot aipiPohl
  • Manihot aypiSpruce
  • Manihot cannabinaSweet
  • Manihot diffusaPohl
  • Manihot digitiformisPohl
  • Manihot dulcis(J.F.Gmel.) Baill.
  • Manihot eduleA.Rich.
  • Manihot edulisA.Rich.
  • Manihot flabellifoliaPohl
  • Manihot flexuosaPax & K.Hoffm.
  • Manihot loureiroiPohl
  • Manihot melanobasisMüll. Arg.
  • Manihot spruceiPax
  • Manihot utilissimaPohl

Manihot esculenta, commonly called cassava ( /kəˈsɑːvə/ ), manioc, [2] yuca, macaxeira, mandioca, aipim and Brazilian arrowroot,[ citation needed ] is a woody shrub native to South America of the spurge family, Euphorbiaceae. It 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 often called yuca in Spanish and in the United States, it is not related to yucca, a shrub in the family Asparagaceae. Cassava, when dried to a powdery (or pearly) extract, is called tapioca; its fried, granular form is named garri .

In biology, a common name of a taxon or organism is a name that is based on the normal language of everyday life; this kind of name is often contrasted with the scientific name for the same organism, which is Latinized. A common name is sometimes frequently used, but that is by no means always the case.

Shrub type of plant

A shrub or bush is a small- to medium-sized woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. They are distinguished from trees by their multiple stems and shorter height, and are usually under 6 m (20 ft) tall. Plants of many species may grow either into shrubs or trees, depending on their growing conditions. Small, low shrubs, generally less than 2 m (6.6 ft) tall, such as lavender, periwinkle and most small garden varieties of rose, are often termed "subshrubs".

Contents

Cassava is the third-largest source of food carbohydrates in the tropics, after rice and maize. [3] [4] Cassava is a major staple food in the developing world, providing a basic diet for over half a billion people. [5] 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.

Rice cereal grain and seed of Oryza sativa

Rice is the seed of the grass species Oryza sativa or Oryza glaberrima. As a cereal grain, it is the most widely consumed staple food for a large part of the world's human population, especially in Asia. It is the agricultural commodity with the third-highest worldwide production, after sugarcane and maize.

Maize Cereal grain

Maize, also known as corn, is a cereal grain first domesticated by indigenous peoples in southern Mexico about 10,000 years ago. The leafy stalk of the plant produces pollen inflorescences and separate ovuliferous inflorescences called ears that yield kernels or seeds, which are fruits.

Staple food food that is eaten routinely and considered a dominant portion of a standard diet

A staple food, food staple, or simply a staple, is a food that is eaten routinely and in such quantities that it constitutes a dominant portion of a standard diet for a given people, supplying a large fraction of energy needs and generally forming a significant proportion of the intake of other nutrients as well. A staple food of a specific society may be eaten as often as every day or every meal, and most people live on a diet based on just a small number of food staples. Specific staples vary from place to place, but typically are inexpensive or readily available foods that supply one or more of the macronutrients needed for survival and health: carbohydrates, proteins, and fats. Typical examples include tubers and roots, grains, legumes, and seeds.

Cassava is classified as either sweet or bitter. Like other roots and tubers, both bitter and sweet varieties of cassava contain antinutritional factors and toxins, with the bitter varieties containing much larger amounts. [6] It must be properly prepared before consumption, as improper preparation of cassava can leave enough residual cyanide to cause acute cyanide intoxication, [7] [8] goiters, and even ataxia, partial paralysis, or death. The more toxic varieties of cassava are a fall-back resource (a "food security crop") in times of famine or food insecurity in some places. [7] [6] Farmers often prefer the bitter varieties because they deter pests, animals, and thieves. [9]

Antinutrient natural or synthetic compounds that interfere with the absorption of nutrients

Antinutrients are natural or synthetic compounds that interfere with the absorption of nutrients. Nutrition studies focus on these antinutrients commonly found in food sources and beverages.

Cyanide any chemical compound with cyanide anion

A cyanide is a chemical compound that contains the group C≡N. This group, known as the cyano group, consists of a carbon atom triple-bonded to a nitrogen atom.

Cyanide poisoning human disease

Cyanide poisoning is poisoning that results from exposure to a number of forms of cyanide. Early symptoms include headache, dizziness, fast heart rate, shortness of breath, and vomiting. This may then be followed by seizures, slow heart rate, low blood pressure, loss of consciousness, and cardiac arrest. Onset of symptoms is usually within a few minutes. If a person survives, there may be long-term neurological problems.

Description

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 cultivars 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 vascular bundle runs along the root's axis. The flesh can be chalk-white or yellowish. Cassava roots are very rich in starch and contain small amounts of calcium (16 mg/100 g), phosphorus (27 mg/100 g), and vitamin C (20.6 mg/100 g). [10] 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. [11]

Cultivar plant or grouping of plants selected for desirable characteristics

The term cultivar most commonly refers to an assemblage of plants selected for desirable characters that are maintained during propagation. More generally, cultivar refers to the most basic classification category of cultivated plants in the International Code of Nomenclature for Cultivated Plants (ICNCP). Most cultivars arose in cultivation, but a few are special selections from the wild.

Starch carbohydrate consisting of a large number of glucose units joined by glycosidic bonds

Starch or amylum is a polymeric carbohydrate consisting of a large number of glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants as energy storage. It is the most common carbohydrate in human diets and is contained in large amounts in staple foods like potatoes, wheat, maize (corn), rice, and cassava.

Protein biological molecule consisting of chains of amino acid residues

Proteins are large biomolecules, or macromolecules, consisting of one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, responding to stimuli, providing structure to cells and organisms, and transporting molecules from one location to another. Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the nucleotide sequence of their genes, and which usually results in protein folding into a specific three-dimensional structure that determines its activity.

Details of cassava plants
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Unprocessed roots
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Leaf
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Leaf detail
Cassava buds (4733912948).jpg
Picked buds
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Seeds

History

17th c. painting by Albert Eckhout in Dutch Brazil Albert Eckhout - Mandioca.jpg
17th c. painting by Albert Eckhout in Dutch Brazil

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. [12] Forms of the modern domesticated species can also be found growing in the wild in the south of Brazil. By 4,600 BC, manioc (cassava) pollen appears in the Gulf of Mexico lowlands, at the San Andrés archaeological site. [13] The oldest direct evidence of cassava cultivation comes from a 1,400-year-old Maya site, Joya de Cerén, in El Salvador. [14] 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 European contact in 1492. Cassava was a staple food of pre-Columbian peoples in the Americas and is often portrayed in indigenous art. The Moche people often depicted yuca in their ceramics. [15]

Before Present (BP) years is a time scale used mainly in archaeology, geology and other scientific disciplines to specify when events occurred in the past. Because the "present" time changes, standard practice is to use 1 January 1950 as the commencement date of the age scale, reflecting the origin of practical radiocarbon dating in the 1950s. The abbreviation "BP" has alternatively been interpreted as "Before Physics"; that is, before nuclear weapons testing artificially altered the proportion of the carbon isotopes in the atmosphere, making dating after that time likely to be unreliable.

Gulf of Mexico An Atlantic Ocean basin extending into southern North America

The Gulf of Mexico is an ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. The U.S. states of Texas, Louisiana, Mississippi, Alabama, and Florida border the Gulf on the north, which are often referred to as the "Third Coast", in comparison with the U.S. Atlantic and Pacific coasts.

San Andrés (Mesoamerican site)

San Andrés is an Olmec archaeological site in the present-day Mexican state of Tabasco. Located 5 km northeast of the Olmec ceremonial center of La Venta in the Grijalva river delta section of the Tabasco Coastal Plain, San Andrés is considered one of its elite satellite communities, with evidence of elite residences and other elite activities. Several important archaeological finds have been made at San Andrés, including the oldest evidence of the domesticated sunflower, insight into Olmec feasting rituals, didactic miniatures, and possible evidence of an Olmec writing system.

Spaniards in their early occupation of Caribbean islands did not want to eat cassava or maize, which they considered insubstantial, dangerous, and not nutritious. They much preferred foods from Spain, specifically wheat bread, olive oil, red wine, and meat, and considered maize and cassava damaging to Europeans. For these Christians in the New World, cassava was not suitable for communion since it could not undergo transubstantiation and become the body of Christ. "Wheat flour was the symbol of Christianity itself" and colonial-era catechisms stated explicitly that only wheat flour could be used. [16]

New World Collectively, the Americas and Oceania

The New World is one of the names used for the majority of Earth's Western Hemisphere, specifically the Americas, and Oceania.

Transubstantiation Catholic doctrine that the body and blood of Jesus are present in Eucharist

Transubstantiation is, according to the teachings of the Roman Catholic Church, the change of substance or essence by which the bread and wine offered in the sacrifice of the sacrament of the Eucharist during the Mass, become, in reality, the body and blood of Jesus Christ.

The cultivation and consumption of cassava was nonetheless continued in both Portuguese and Spanish America. Mass production of cassava bread became the first Cuban industry established by the Spanish, [17] Ships departing to Europe from Cuban ports such as Havana, Santiago, Bayamo, and Baracoa carried goods to Spain, but sailors needed to be provisioned for the voyage. The Spanish also needed to replenish their boats with dried meat, water, fruit, and large amounts of cassava bread. [18] Sailors complained that it caused them digestive problems. [19] Tropical Cuban weather was not suitable for wheat planting and cassava would not go stale as quickly as regular bread.

Cassava was introduced to Africa by Portuguese traders from Brazil in the 16th century. Around the same period, it was also introduced to Asia through Columbian Exchange by Portuguese and Spanish traders, planted in their colonies in Goa, Malacca, Eastern Indonesia, Timor and the Philippines. Maize and cassava are now important staple foods, replacing native African crops. [20] Cassava has also become an important staple in Asia, extensively cultivated in Indonesia, Thailand and Vietnam. [21] Cassava is sometimes described as the "bread of the tropics" [22] but should not be confused with the tropical and equatorial bread tree (Encephalartos), the breadfruit (Artocarpus altilis) or the African breadfruit (Treculia africana).

Production

In 2016, global production of cassava root was 277 million tonnes, with Nigeria as the world's largest producer having 21% of the world total (table). Other major growers were Thailand, Brazil, and Indonesia. [23]

Cassava production – 2016
CountryProduction (millions of tonnes)
Flag of Nigeria.svg  Nigeria
57.1
Flag of Thailand.svg  Thailand
31.1
Flag of Brazil.svg  Brazil
21.1
Flag of Indonesia.svg  Indonesia
20.7
Flag of the Democratic Republic of the Congo.svg  Democratic Republic of the Congo
14.7
World
277.1
Source: FAOSTAT of the United Nations [23]

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 from 50 mm (2.0 in) 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 when considering 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 kcal/hectare/day, as compared with 176 for rice, 110 for wheat and 200 for maize (corn).

Economic importance

A cassava tuber in cross-section Manihot esculenta - cross section 2.jpg
A cassava tuber in cross-section

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. [24] 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. [25]

Worldwide, 800 million people depend on cassava as their primary food staple. [26] 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, it is either a primary staple food or a secondary costaple. In Ghana, for example, cassava and yams occupy an important position in the agricultural economy and contribute about 46 percent of the agricultural gross domestic product. Cassava accounts for a daily caloric intake of 30 percent 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".

In Tamil Nadu, India, there are many cassava processing factories alongside National Highway 68 between Thalaivasal and Attur. Cassava is widely cultivated and eaten as a staple food in Andhra Pradesh and in Kerala. In Assam it is an important source of carbohydrates especially 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 percent of cassava production in China is concentrated in a single province, Guangxi, averaging over seven million tonnes annually.

Uses

Processing cassava starch into cassava noodles, Kampong Cham Cambodia16 lo (4039995158).jpg
Processing cassava starch into cassava noodles, Kampong Cham

Alcoholic beverages

Alcoholic beverages made from cassava include cauim and tiquira (Brazil), kasiri (Guyana, Suriname), impala (Mozambique), masato (Peruvian Amazonia chicha), parakari or kari (Guyana), nihamanchi (South America) also known as nijimanche (Ecuador and Peru), ö döi (chicha de yuca, Ngäbe-Bugle, Panama), sakurá (Brazil, Suriname), and tarul ko jaarh (Darjeeling, Sikkim, India).

Culinary

Cassava heavy cake Cassava heavy cake.jpg
Cassava heavy cake

Cassava-based dishes are widely consumed wherever the plant is cultivated; some have regional, national, or ethnic importance. [27] Cassava must be cooked properly to detoxify it before it is eaten.

Cassava can be cooked in many ways. The root of the sweet variety has a delicate flavor and can replace potatoes. It is used in cholent in some households.[ citation needed ] 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 farofa used as a condiment, toasted in butter, or eaten alone as a side dish.

Nutritional profile

Cassava, raw
Nutritional value per 100 g (3.5 oz)
Energy 160 kcal (670 kJ)
38.1 g
Sugars 1.7 g
Dietary fiber 1.8 g
Fat
0.3 g
1.4 g
Vitamins Quantity%DV
Thiamine (B1)
8%
0.087 mg
Riboflavin (B2)
4%
0.048 mg
Niacin (B3)
6%
0.854 mg
Vitamin B6
7%
0.088 mg
Folate (B9)
7%
27 μg
Vitamin C
25%
20.6 mg
Minerals Quantity%DV
Calcium
2%
16 mg
Iron
2%
0.27 mg
Magnesium
6%
21 mg
Phosphorus
4%
27 mg
Potassium
6%
271 mg
Sodium
1%
14 mg
Zinc
4%
0.34 mg
Other constituentsQuantity
Water60 g

Percentages are roughly approximated using US recommendations for adults.

Raw cassava is 60% water, 38% carbohydrates, 1% protein, and has negligible fat (table). [28] In a 100 gram amount, raw cassava provides 160 calories and contains 25% of the Daily Value (DV) for vitamin C, but otherwise has no micronutrients in significant content (no values above 10% DV; table). Cooked cassava starch has a digestibility of over 75%. [28]

Cassava, like other foods, also has antinutritional and toxic factors. Of particular concern are the cyanogenic glucosides of cassava (linamarin and lotaustralin). On hydrolysis, these release hydrocyanic acid (HCN).[ citation needed ] 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 simply boiling.

Comparison with other major staple foods

A comparative table shows that cassava is a good energy source. In its prepared forms in which its toxic or unpleasant components have been reduced to acceptable levels, it contains an extremely high proportion of starch. Compared to most staples however, cassava accordingly is a poorer dietary source of protein and most other essential nutrients. Though an important staple, its main value is as a component of a balanced diet.

Comparisons between the nutrient content of cassava and other major staple foods when raw, as shown in the table, must be interpreted with caution because most staples are not edible in such forms and many are indigestible, even dangerously poisonous or otherwise harmful.[ citation needed ] For consumption, each must be prepared and cooked as appropriate. Suitably cooked or otherwise prepared, the nutritional and antinutritional contents of each of these staples is widely different from that of raw form and depends on the methods of preparation such as soaking, fermentation, sprouting, boiling, or baking.

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 Eleventh Five-Year Plan in the People's Republic of China, the target is to increase the production of ethanol fuel from nongrain feedstock to two million tonnes, and that of biodiesel to 200 thousand tonnes by 2010. This is equivalent to the replacement of 10 million tonnes of petroleum. As a result, cassava (tapioca) chips have gradually become a major source of ethanol production. [29] On 22 December 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 invested US$51.5 million in a new biofuel facility that is expected to produce 33 million US gallons (120,000 m3) a year of bioethanol from cassava plants. [30]

Animal feed

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Close-up of grated cassava.jpg
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Tubers being grated; a close-up of the product; drying on road to be used for pig and chicken feed

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 its final dry matter content approaches 85 percent. Cassava hay contains high protein (20–27 percent crude protein) and condensed tannins (1.5–4 percent CP). It is valued as a good roughage source for ruminants such as cattle. [31]

Laundry starch

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.

Medicinal use

According to the American Cancer Society, cassava is ineffective as an anti-cancer agent: "there is no convincing scientific evidence that cassava or tapioca is effective in preventing or treating cancer". [32]

Food use

A woman washes cassava in a river A woman washes cassava in rural DRC (7609952020).jpg
A woman washes cassava in a river

Potential 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). [33] 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. [34] [35] A dose of 25 mg of pure cassava cyanogenic glucoside, which contains 2.5 mg of cyanide, is sufficient to kill a rat. [36] 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 ). [6] It has also been linked to tropical calcific pancreatitis in humans, leading to chronic pancreatitis. [37]

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). [6]

"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 three percent in some areas." [38] [39]

During the shortages in Venezuela in the late-2010s, dozens of deaths were reported due to Venezuelans resorting to eating bitter cassava in order to curb starvation. [40] [41]

Societies that traditionally eat cassava generally understand that some processing (soaking, cooking, fermentation, etc.) is necessary to avoid getting sick. 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. [6]

Cassava root, peeled and soaking PeeledCassava.jpg
Cassava root, peeled and soaking

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. [33] 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 flow with the water during the soaking process are also used in cooking. [42] 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. [33]

Food preparation

Cassava bread Cassava bread.jpg
Cassava bread

A safe processing method known as the "wetting method" 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. [43] 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. [43]

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, Cameroon, 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. [44] 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. [45] [46]

A project called "BioCassava Plus" uses bioengineering to grow cassava with lower cyanogenic glycosides combined with fortification of vitamin A, iron and protein to improve the nutrition of people in sub-Saharan Africa. [47] [48]

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. [49]

Postharvest handling and storage

Cassava undergoes post-harvest physiological deterioration (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, starts 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. PPD is related to the accumulation of reactive oxygen species (ROS) initiated by cyanide release during mechanical harvesting. Cassava shelf life may be increased up to three weeks by overexpressing a cyanide insensitive alternative oxidase, which suppressed ROS by 10-fold. [50] PPD is one of the main obstacles preventing farmers from exporting cassavas abroad and generating income. Fresh cassava can be preserved like potato, using thiabendazole or bleach as a fungicide, then wrapping in plastic, coating in wax or freezing. [51]

While alternative methods for PPD control have been proposed, such as preventing ROS effects by use of plastic bags during storage and transport or coating the roots with wax, and freezing roots, such strategies have proved to be economically or technically impractical, leading to breeding of cassava varieties more tolerant to PPD and with improved durability after harvest. [52] Plant breeding has resulted in different strategies for cassava tolerance to PPD. [52] [53] One was induced by mutagenic levels of gamma rays, which putatively silenced one of the genes involved in PPD genesis, while another was a group of high-carotene clones in which the antioxidant properties of carotenoids are postulated to protect the roots from PPD. [53]

Pests

A major cause of losses during cassava storage is infestation by insects. [54] A wide range of species that feed directly on dried cassava chips have been reported as a major factor in spoiling stored cassava, with losses between 19% and 30% of the harvested produce. [54] In Africa, a previous issue was the cassava mealybug ( Phenacoccus manihoti ) and cassava green mite ( Mononychellus tanajoa ). These pests can cause up to 80 percent 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 International Institute of Tropical Agriculture (IITA) under the leadership of Hans Rudolf Herren. [55] 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 African cassava mosaic virus causes the leaves of the cassava plant to wither, limiting the growth of the root. [56] An outbreak of the virus in Africa in the 1920s led to a major famine. [57] 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 spread at a rate of 50 mi (80 km) per year, and as of 2005 was found throughout Uganda, Rwanda, Burundi, the Democratic Republic of the Congo and the Republic of the Congo. [58]

Cassava brown streak virus disease has been identified as a major threat to cultivation worldwide. [57]

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. [59] 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. [60] 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. [61] 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. [62]

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. [63] [64] [60] [65] 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. [61]

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. [66] The organophosphorus 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; the use of tolerant and resistant cultivars is the most practical and sustainable management method. [61]

See also

Related Research Articles

Tapioca starch extracted from cassava root (Manihot esculenta)

Tapioca is a starch extracted from cassava plant. This species is native to the north region and central-west region of Brazil, but its use spread throughout South America. The plant was carried by Portuguese and Spanish explorers to most of the West Indies and Africa and Asia. It is a tropical, perennial shrub that is less commonly cultivated in temperate climate zones. Cassava thrives better in poor soils than many other food plants.

Northern root-knot nematode is a species of vegetable pathogens which produces tiny galls on around 550 crop and weed species. They invade root tissue after birth. Females are able to lay up to 1,000 eggs at a time in a large egg mass. By surviving harsh winters, they can survive in cold climates.

<i>Colocasia esculenta</i> species of plant, taro

Colocasia esculenta is a tropical plant grown primarily for its edible corms, the root vegetables most commonly known as taro. It is the most widely cultivated species of several plants in the Araceae family which are used as vegetables for their corms, leaves, and petioles. Taro corms are a food staple in African, Oceanic and South Asian cultures, and taro is believed to have been one of the earliest cultivated plants.

Root-knot nematode genus of worms

Root-knot nematodes are plant-parasitic nematodes from the genus Meloidogyne. They exist in soil in areas with hot climates or short winters. About 2000 plants worldwide are susceptible to infection by root-knot nematodes and they cause approximately 5% of global crop loss. Root-knot nematode larvae infect plant roots, causing the development of root-knot galls that drain the plant's photosynthate and nutrients. Infection of young plants may be lethal, while infection of mature plants causes decreased yield.

Yam (vegetable) vegetable

Yam is the common name for some plant species in the genus Dioscorea that form edible tubers. Yams are perennial herbaceous vines cultivated for the consumption of their starchy tubers in many temperate and tropical world regions. The tubers themselves are also called "yams", having numerous cultivars and related species.

Linamarin chemical compound

Linamarin is a cyanogenic glucoside found in the leaves and roots of plants such as cassava, lima beans, and flax. It is a glucoside of acetone cyanohydrin. Upon exposure to enzymes and gut flora in the human intestine, linamarin and its methylated relative lotaustralin can decompose to the toxic chemical hydrogen cyanide; hence food uses of plants that contain significant quantities of linamarin require extensive preparation and detoxification. Ingested and absorbed linamarin is rapidly excreted in the urine and the glucoside itself does not appear to be acutely toxic. Consumption of cassava products with low levels of linamarin is widespread in the low-land tropics. Ingestion of food prepared from insufficiently processed cassava roots with high linamarin levels has been associated with dietary toxicity, particularly with the upper motor neuron disease known as konzo to the African populations in which it was first described by Trolli and later through the research network initiated by Hans Rosling. However, the toxicity is believed to be induced by ingestion of acetone cyanohydrin, the breakdown product of linamarin. Dietary exposure to linamarin has also been reported as a risk factor in developing glucose intolerance and diabetes, although studies in experimental animals have been inconsistent in reproducing this effect and may indicate that the primary effect is in aggravating existing conditions rather than inducing diabetes on its own.

Lotaustralin chemical compound

Lotaustralin is a cyanogenic glucoside found in small amounts in Fabaceae Austral Trefoil, cassava, lima bean, roseroot and white clover, among other plants. Lotaustralin is the glucoside of methyl ethyl ketone cyanohydrin and is structurally related to linamarin, the acetone cyanohydrin glucoside also found in these plants. Both lotaustralin and linamarin may be hydrolyzed by the enzyme linamarase to form glucose and a precursor to the toxic compound hydrogen cyanide.

<i>Tacca leontopetaloides</i> species of plant

Tacca leontopetaloides is a species of flowering plant in the yam family Dioscoreaceae. It is native to Island Southeast Asia but have been introduced as canoe plants throughout the Indo-Pacific tropics by Austronesian peoples during prehistoric times. They have become naturalized to tropical Africa, South Asia, northern Australia, and Oceania. Common names include Polynesian arrowroot, Fiji arrowroot, East Indies arrowroot, and pia.

Meloidogyne javanica is a species of plant-pathogenic nematodes. It is one of the tropical root-knot nematodes and a major agricultural pest in many countries. It has many hosts. Meloidogyne javanica reproduces by obligatory mitotic parthenogenesis (apomixis).

A great variety of cassava-based dishes are consumed in the regions where cassava is cultivated, and they include many national or ethnic specialities.

<i>Ensete ventricosum</i> species of plant

Ensete ventricosum, commonly known as the Ethiopian banana, Abyssinian banana, false banana, enset or ensete, is an herbaceous species of flowering plant in the banana family Musaceae. The domesticated form of the plant is only cultivated in Ethiopia, where it provides the staple food for approximately 20 million people. The name Ensete ventricosum was first published in 1948 in the Kew Bulletin, 1947, p. 101. Its synonyms include Musa arnoldiana De Wild., Musa ventricosa Welw. and Musa ensete J.F.Gmel. In its wild form, it is native to the eastern edge of the Great African Plateau, extending northwards from South Africa through Mozambique, Zimbabwe, Malawi, Kenya, Uganda and Tanzania to Ethiopia, and west to the Congo, being found in high rainfall forests on mountains, and along forested ravines and streams.

<i>Manihot walkerae</i> species of plant

Manihot walkerae, commonly known as Walker's manihot, is a species of flowering plant in the spurge family, Euphorbiaceae, that is native to the Lower Rio Grande Valley of Texas in the United States and Tamaulipas in Mexico. The specific name honours amateur botanist Thelma Ratcliff Walker, who discovered the type specimen near Mission and La Joya, Texas in 1942.

Yam production in Nigeria

Nigeria is by far the world’s largest producer of yams, accounting for over 70–76 percent of the world production. According to the Food and Agriculture Organization report, in 1985, Nigeria produced 18.3 million tonnes of yam from 1.5 million hectares, representing 73.8 percent of total yam production in Africa. According to 2008 figures, yam production in Nigeria has nearly doubled since 1985, with Nigeria producing 35.017 million metric tonnes with value equivalent of US$5.654 billion. In perspective, the world's second and third largest producers of yams, Côte d'Ivoire and Ghana, only produced 6.9 and 4.8 million tonnes of yams in 2008 respectively. According to the International Institute of Tropical Agriculture, Nigeria accounted for about 70 percent of the world production amounting to 17 million tonnes from land area 2,837,000 hectares under yam cultivation.

Yellow cassava is a new, yellow-fleshed breed of one of the most popular root crops in the tropics. Regular cassava is a staple crop in tropical countries which 300 million people rely upon for at least 10% of their daily caloric intake, in 15 African countries “In the Democratic Republic of the Congo, cassava is estimated to provide more than 1000 kcal/day to over 40 million people”. Three yellow root cassava varieties, UMUCASS 36, UMUCASS 37, and UMUCASS 38, are being grown in Nigeria for their high concentrations of β-carotene. β-carotene is a precursor to Vitamin A. Vitamin A deficiency is a major issue, especially in Africa. Nigeria in particular sees a prevalence of Vitamin A deficiency in nearly one third of children under five years old. Since cassava is a major food staple, yellow cassava shows great potential to alleviate Vitamin A deficiency in Africa.

Arrowroot is a starch obtained from the rhizomes (rootstock) of several tropical plants, traditionally Maranta arundinacea, but also Florida arrowroot from Zamia integrifolia, and tapioca from cassava, which is often labelled as arrowroot. Polynesian arrowroot or pia, and Japanese arrowroot, also called kudzu, are used in similar ways.

Arrowroot refers to an edible starch obtained from several tropical plants, these include:

Cassava production in Nigeria

Cassava production is vital to the economy of Nigeria as the country is the world's largest producer of the commodity. The crop is produced in 24 of the country's 36 states. In 1999, Nigeria produced 33 million tonnes, while a decade later, it produced approximately 45 million tonnes, which is almost 19% of production in the world. The average yield per hectare is 10.6 tonnes.

Cassava production in the Democratic Republic of the Congo

Cassava production is important to the economy of Democratic Republic of the Congo (DRC). It is one of the country's principal crops, with per capita consumption of 353 kg per year, which is the highest in the world. Zaire, now the DRC, was the world's largest consumer of cassava with Republic of the Congo ranked second in 1996.

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