Manioc Root

Infobox on Manioc Root
Example of Manioc Root
Facts
Origin	-
Stowage factor (in m3/t)	-
Humidity / moisture	-
Ventilation	-
Risk factors	See text

Manioc Root

Description

Cassava (Manihot esculenta), also called manioc, yuca, balinghoy, mogo, mandioca, kamoteng kahoy, and manioc root, 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. It differs from the similarly spelled yucca, an unrelated fruit-bearing shrub in the Asparagaceae family. Cassava, when dried to a starchy, 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 world. 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.

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

Cassava is classified as sweet or bitter. Like other roots and tubers, cassava contains 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. Nevertheless, farmers often prefer the bitter varieties because they deter pests, animals, and thieves. The more-toxic varieties of cassava are a fall-back resource (a "food security crop") in times of famine in some places.

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

Cassava root is essentially a carbohydrate source. Its composition shows 60–65% moisture, 20–31% carbohydrate, 1–2% 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% amylopectin and 20% amylose. Cooked cassava starch has a digestibility of over 75%.

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

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

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

Cassava, like other foods, also has antinutritional and toxic factors. Of particular concern are the cyanogenic glucosides of cassava (linamarin and lotaustralin). These, on hydrolysis, 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, cassava must be treated and prepared properly prior to human or animal consumption.

Application

Cassava-based dishes are widely consumed wherever the plant is cultivated; some have regional, national, or ethnic importance.[20] Cassava must be cooked properly to detoxify it before it is eaten.

Cassava can be cooked in many ways. The soft-boiled root has a delicate flavor and can replace boiled potatoes in many uses: as an accompaniment for meat dishes or made into purées, dumplings, soups, stews, gravies, etc. This plant is used in cholent, in some households, as well. Deep fried (after boiling or steaming), it can replace fried potatoes, with a distinctive flavor. In Brazil, detoxified manioc is ground and cooked to a dry, often hard or crunchy meal which is used as a condiment, toasted in butter, or eaten alone as a side dish.

Cassava is used worldwide for animal feed, as well. Cassava hay is produced at a young growth stage at three to four months, harvested about 30–45 cm above ground, and sun-dried for one to two days until it has final dry matter of less than 85%. The cassava hay contains high protein (20–27% crude protein) and condensed tannins (1.5–4% CP). It is used as a good roughage source for dairy or beef cattle, buffalo, goats, and sheep by either direct feeding or as a protein source in the concentrate mixtures.

Shipment / Storage / Risk factors

The root of a shrub from which the starch is extracted. Used in the manufacture of tapioca, laundry starch and adhesive. Shipped in sacks and bags. Manioc roots should be white, hard and well shelled, and stored in a dry fresh place whenever possible. With time the hardness will tend to disappear, due to its many sortings. Storage in damp places or placing in sacks before properly dry may cause the formation of a greenish mould. If slight this is merely a film which disappears on brushing.

In serious cases the mould may be of dark green or black appearance, being rotten, which will be indicated by dark patches on the sacks in the areas contaminated. In fresh produce, live weevil can only be discovered by cutting open the pieces. A soft cake will indicate that the produce is old, and powdered, a quantity of white dust being noted when handled. A dust other than white might indicate that the manioc is adulterated.

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.

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. Frozen cassava leaves from the Philippines sold at a Los Angeles market

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 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. 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.

See also Cassava Meal