Yucca - Cassava

1. Yucca - Cassava (Manihot esculenta) Classification

Kingdom: Plantae (Plants)
Subkingdom: Tracheobionta (Vascular Plants)
Superdivision: Spermatophyta (Seed Plants)
Division: Magnoliophyta (Flowering Plants)
Class: Magnoliopsida (Dicotyledons)
Subclass: Rosidae
Order: Euphorbiales
Family: Euphorbiaceae (Euphorbs; Spurge Family)
Genus: Manihot
Species: Manihot esculenta Crantz
Synonyms:

• Manihot utilissima Phol.
• Manihot aipi Phol.
• Jatropha manihot L.

Related Species:

• Manihot dulcis

Common Names: “cassava”, “yuca”, “bitter cassava”, “tapioca”, “tapioca plant”, “manioc”, “Brazilian arrowroot”, “sweet potato tree”. Spanish: Peru “yuca”; Western Indies “cassava”. Thai: “dang noi”, “man sum palung”, “pearks sakhoo”. Others: “tapioca”, “manioca”, “huacamote”.

2. Yucca - Cassava Description

Habit: Exuberant herb, woody shrub, or even small tree, cultivated as annual (although this is a perennial plant species), much branching, between 1.3 m and 5 m tall. The whole plant contains cyanogenic glycosides.

Leaves: The leaves present long petioles. They are generally palmately divided (finger-shaped) in 3 to 7 lobes. These lobes are spatulate to linear-lanceolate, acuminate, between 7.5 cm to 15 cm long, glabrous, glaucous (light green) at the abaxial surface (beneath) and minutely puberulent along the veins. There exist many variations depending on cultivars.

Flowers: The flowers are yellow-greenish, measuring less than 1.2 cm in length, and arranged in panicles.

Fruit: The fruit is a globose capsule, 1.2 cm in diameter, with 6-winged ribs. Each capsule contains three seeds.

Root: The roots are tuberous, fleshy, farinaceous, up to 90 cm in length (although roots up to 2.5 m have been registered), up to 15 cm in diameter (most frequently near 8 cm) and edible. The roots can weight up to 40 kg, although the average is between 4 kg and 7 kg. The pulp is usually white, although there exist some few cultivars with yellow pulp. The roots contain a venomous volatile chemical compound that is eliminated by means of heat.

Chromosomal number: 2n = 36

3. Yucca - Cassava Origin, Distribution and Ecology

Origin: This plant species is native to the tropical regions of South America. Its centre of origin maybe is located between Brazil and Paraguay. Manihot esculenta is considered a cultigen with no wild forms known.

Distribution: Manihot esculenta distributes throughout Tropical America. The cultivation of this plant species has extended out of America, in Asia and especially Africa, where Manihot esculenta is a very important crop. The region comprising Indonesia and Indochina is considered as a secondary center of diversity. In the United States, Manihot esculenta is scarcely cultivated; the few crop fields are located in the Southern States where this plant species is used as fodder for cattle. This is one of the major sources of starch found in the tropical regions around the world.

Ecology: Manihot esculenta is a tropical crop that requires at least 8 warm months. Traditionally, this plant species grows in savanna-like climates, although it can grow under intense rainfall. Manihot esculenta has also adapted to subtropical regions. In wet areas, Manihot esculenta does not tolerate inundations; in dry regions, this plant species let its leaves fall in order to maintain its humidity and produces new leaves when rainfall restarts. Under severe adverse climates, such as intense cold or drought, Manihot esculenta requires at least 18 months in order to produce harvestable roots. This plant species does not tolerate frosts. It tolerates a wide range of soil pH (4.0 to 8.0). It grows better under full sunlight.

· Sunlight: Manihot esculenta develops well under full sunlight or slight shadow. When planted for root production, full sunlight is required.

· Water requirements: The soil where Manihot esculenta is to be planted has to be constantly humid. Soil hilling around the plants is recommended in order to maintain humidity.

· Propagation: Manihot esculenta propagates easily from terminal cuts (7 cm to 30 cm) of the stem. The lowermost half has to be buried. The typical spacing is 1 meter. The seeds are used for genetic improvement purposes only.

· Fertilization: In the United States, the fields with Manihot esculenta are customarily fertilized in spring. Fertilization is carried out only during the first months of cultivation.

· Plague control: Neither commercial fungicides nor pesticides are commonly used.

· Harvest: Manihot esculenta does not goes through a mature period. It can be harvested at any moment after the plant has developed succulent roots, approximately 8 months after seeding. Harvest time depends on the root size the consumers demand. Harvest can be delayed for more than one season, although the pith of the roots tend to lignify and become inedible. The shrubs of Manihot esculenta can be cut and used as fodder when they are 3 to 4 months old. They are cut at 40 cm from the ground level and then chopped finely by hand or a fodder chopper.

· Yield: Under the best conditions, it is possible to obtain near 80 MT of fresh root per hectare, although the average worldwide yield is 9.8 MT per hectare. On the other hand, an appropriate agronomical management conducted in order to harvest the foliage can yield more than 6 MT of crude protein per hectare per year.

4. Yucca - Cassava History

This plant species is native to South America, although it is also cultivated in Central America and Africa. Manihot esculenta Crantz is closely associated to the Arawak ethnic group, one of the most widespread in America. This ethnic group settled from the Western Indies to Paraguay. It is very likely that tribes belonging to this ethnic group have been responsible for the domestication of this plant species. They also probably discovered the way to eliminate its venom.

Effectively, the roots of Manihot esculenta are extremely venomous when raw. The Amerindians in South America have learned since much time ago that rinsing the roots the venom is eliminated. In order to do this, they put the smashed roots on nets and then soak and crush them.

The toxic substances present in the roots can also be eliminated by slicing minutely the roots and letting the thin slices to dry during near 2 weeks. Cooking also eliminates the prussic acid it contains, thus resulting perfectly edible. Modern cultivars have so few cyanogenic glycosides that more than 1 kg of raw roots would be needed in order to get intoxicated.

The cultivation of Manihot esculenta is very old. The high number of cultivars that exist along Tropical America (near 160 or more) are an evidence of its old cultivation. All the cultivars can be put in 2 major groups: bitter and sweet.

The bitter cultivars have typically straight stems, almost red and big leaves and enormous precocious yields. They are characterized especially by their high content of prussic acid, between 0.02% and 0.03%. Because of their high content of prussic acid, bitter cultivars are dedicated mainly to the industrial production of starch.

On the other hand, sweet cultivars contain near 0.007% prussic acid, most of the acid being concentrated both in the peel and the outermost cortical layer of the roots. They are used as food for humans and animals.

The major use of the roots of Manihot esculenta has always been as a low cost energy food due to their high content of starch (30%). In South America, a juice obtained from the root is used in order to elaborate an alcoholic beverage that in Peru is known as masato.

In Brazil, the flour obtained from the roots is used in order to prepare thin tortillas known as pan de mandioca (mandioca bread). In Africa, the roots are also customarily dehydrated and converted in flour, which is also fermented. Manihot esculenta arrived to Africa from America carried by Portuguese merchants.

The roots constitute a major source of low cost carbohydrates for populations in tropical wet regions. Today, Manihot esculenta constitutes a staple food, especially in Western and Central Africa. The main producer is Brazil, followed by Thailand, Nigeria, Zaire, and Indonesia. The production in Africa and Asia is increasing, whereas in Latin America it remains stable since near 30 years ago. The greatest exporter of Manihot esculenta is Thailand, and the main source of Thailand’s Manihot esculenta is Europe.

Manihot esculenta has also an industrial use for the elaboration of paper, clothes, adhesives, fructose-rich syrups and alcohol. In India, Manihot esculenta is the second most important tuberous crop. Modernly, the properties of Manihot esculenta in medicine are being studied.

5. Yucca - Cassava Uses

Parts Used:

Roots, leaves.

· Roots: The roots are the most important parts of this plant species. They contain starch in a concentration of approximately 30% and very few proteins. The roots are used in a very similar way to potatoes. They can be peeled, cooked, baked, or fried. However, these roots should never be eaten raw, because they have cyanogenic glycosides in a potentially toxic concentration. These cyanogenic glycosides are transformed in hydrocyanic acid (HCN) in the presence of linamarase, a natural enzyme that is released when the cells are broken. These venomous substances are reduced to innocuous levels by means of heat during the cooking.

Traditionally, in South America the roots are grated and crushed in order to extract the juice. From the roots tapioca is obtained. Tapioca is a very nutritive feculent food. Once pulverized, a kind of flour is obtained from the roots. In Brazil this flour is known as farinha. From the starch of Manihot esculenta a product called arrurruz of Brazil is extracted. The roots can also be fermented in order to obtain an alcoholic drink. The flour can be rehydrated to a mass in order to prepare dishes or can be added to soups and cooked dishes.

In Africa, the roots are also customarily dehydrated. One way of preparing them is fermenting them first and then letting them dry under sunlight. They are also customarily grated in order to prepare a dense dish.

The fresh roots can also be thinly sliced and then fried, in a similar way to what is done with potato chips. The flour obtained from the roots can also be satisfactorily used to prepare pasta.

The entire roots with peel can be grated and dried in order to be used as food for cattle. Both fresh and dry roots can be eaten by ruminants in different ways (slices, grated, ground). They can be used to feed milch cows, to fatten fleshy animals and to nurse sucklings.

The roots can also be used in order to feed pigs. The addition of flour of Manihot esculenta up to 65% of the ration, preferably as granules, seems not to affect health, quality and general yield when these rations are well balanced. Cereals have also been satisfactorily substituted by this flour in egg-laying hens; the yield determined as number of eggs results very similar, although the weight of each egg results markedly lower due to the deficiency in methionine. This problem can be easily solved by adding methionine supplements.

Chemical composition of roots of Manihot esculenta Crantz (per 100 g)

Finally, the flour obtained from the roots of Manihot esculenta is not attacked by insects. Neither are attacked by insects the concentrated fodder when added 15% of this flour.

· Leaves: Young and tender leaves of Manihot esculenta may be used as green vegetable. They contain a high protein level (8% to 10%, on a fresh-weight basis). They are eaten as if they were spinach, although they have to be cooked thoroughly in order to eliminate their toxic compounds, as these toxic compounds are present here in a higher concentration than in other parts. It is preferable to use the ‘sweet’ varieties, which have less than 0.01% of prussic acid. The leaves can also be used as fodder for cattle.

There exists a particular clone with variegated leaves that is used as ornamental.

Chemical composition of the leaves (per 100 grams):

Properties:

Manihot esculenta is used as/for/against:

• against abscesses
• against cold
• against condyloma (excrescence on the genital organ)
• against conjunctivitis
• against dysentery
• against excrescencies in the eyes
• against furuncles
• against hernias
• against marasmus
• against prostatitis
• against snakebite
• against testicular diseases
• against ulcers and sores
• alleviate bruises
• anti diarrheic
• anti-inflammatory
• antiseptic
• antispasmodic
• antitumoral (cancerous diseases)
• cyanogenetic
• demulcent
• diuretic
• energetic food (farinaceous root)
• laxative
• venom

The main property of Manihot esculenta is related to its energetic value. From its root, low-cost carbohydrates are obtained. The ground roots supply flour. This flour can be mixed with corn meal in order to add protein. The flour obtained from the roots of Manihot esculenta can be used in order to make bread, since this flour can satisfactorily replace wheat flour. In the United States, bread made entirely from flour of Manihot esculenta has been sold in order to satisfy the requirements of consumers suffering from allergy against wheat flour.

The roots can be boiled or fried. From them, starch, flour, ground roots and tapioca can be obtained. Tapioca is used as a thickener for soups and puddings. The industrial starch obtained from the roots also finds use in the alimentary industry, laundries, and paper and clothes industries. From its starch, a glue used in order to stick stamps is also obtained. The inclusion of 35% of leaf- and stem-flour obtained from Manihot esculenta in concentrated food for milch cows has shown good results. The fodder has been used in order to supply derived protein to ruminants receiving urea and molasses.

In Guyana, traditionally they are accustomed to boil the venomous juice obtained from the roots of this plant species until it becomes a species of syrup; then, this syrup is drunk as laxative.

From the fresh roots, a cataplasm used in order to cure ulcers is made. There exists a series of home remedies for tumors. One of this home remedies consists of a decoction of root flour together with fat; other is a decoction of leaves, which are then smashed; another one is obtained by boiling the roots as a mash.

According to Hartwell (1967-1971), folk medicine uses Manihot esculenta in order to treat cancer, condyloma, excrescences of the eyes, and tumors. It has also been reported its antiseptic, cyanogenetic, demulcent, diuretic, and venomous properties.

Manihot esculenta is also used popularly against abscesses, furuncles, conjunctivitis, diarrhea, dysentery, cold, hernias, inflammations, marasmus, prostatitis, snakebites, ulcers, spasms, bruises, and testicular diseases (Duke and Wain, 1981).

The young leaves are rich in vitamin B and are also a good remedy against beriberi, especially in places where intake of vitamin B is scarce. If the young leaves are to be eaten, it must be done carefully since these leaves have the highest content in prussic acid of the whole plant. In spite of this, the leaves are known to be eaten as green vegetable in some regions, as well as used as food for pigs.

In the Philippines, the roots are reduced to pulp and then mixed with smashed pulp of coconuts and sugar; all of these is rolled in leaves of banana and then boiled. The final product is a dessert known as suman.

Alcohol obtained after fermentation of the roots can be used as alcoholic drink or as fuel.

Finally, the refuse of the roots, frequently called flour, can be added in the rations for bovine cattle. The refuses of Manihot esculenta is the residual material after extracting starch from the roots. These roots yield approximately the same quantity of starch and refuses, which are less valuable than the whole flour obtained from the whole roots. The starch and refuses obtained from the roots of Manihot esculenta are intensively used in South East Asia in order to feed pigs. There, these products are considered a valuable fodder. It has been used in rations for domestic fowl up to 10%.

Chemical Compounds:

• cyanogenic glycosides
  • linamarin
  • lotaustralin
• essential oils
• saponins
• colorants
• toxins:
  • acetone
  • hydrocyanic acid
  • oxalic acid
  • tryptophan

The whole plant contains free and bounded cyanogenic glycosides, which, in the presence of linamarase, a natural enzyme present in the cells, are converted in hydrocyanic acid (HCN), highly toxic.
Linamarase acts on the cyanogenic glycosides when the cells containing them are broken mechanically. The highest concentrations for these glycosides are in the leaves; in the roots, the peel contains a higher concentration than the pulp.

The concentration of toxic compounds varies according the cultivar. It can be as low as 20 mg of hydrocyanic acid per kilogram of fresh root, and as high as 1 000 mg per kilogram of fresh root. Formerly, the clones with low concentration of hydrocyanic acid were known as ‘sweet’ varieties; the ones with high concentration were known as ‘bitter’ varieties.

The milky sap from the plant contains essential oils (0.13%), saponins (1.14%), glycosides and natural colorants. The essential oils contain sulphides in organic combination.

6. Yucca - Cassava Doses and Contraindications

Doses: Not determined.

Contraindications: This plant species is still being studied.

Drug Interactions: Not reported.

7. Yucca - Cassava Bibliography and References

1. Byrne. D. 1984. Breeding cassava. Plant Breed. Rev. 2:73-134.
2. Cock, J.H. 1982. Cassava: a basic energy source in the tropics. Science 218:755-762.
3. Cock, J.H. 1985. Cassava: new potential for a neglected crop. Westview Press, Boulder, CO
4. Duke, James A. 1983. Handbook of Energy Crops.
5. Kay, D.E. 1973. TPI Crop and Product Digest, 2. Root Crops. Trop. Prod. Inst., London.
6. Leihner, D. 1978. Follow-up evaluation of two harvesting machines. p. 58-59. In: E.J. Webber, J.H. Cock, and A. Chouinard (eds.). Cassava harvesting and processing. Int. Dvpt. Res. Cent., Ottawa.
7. Onwueme, I.C. 1978. The tropical tuber crops: yams, cassava, sweet potato, and cocoyams. Wiley, New York.
8. Rickard, J.E. 1985. Physiological deterioration of cassava roots. J. Sci. Food Agric. 36:167-176.
9. Watson, L., and Dallwitz, M. J. (1992 onwards). ‘The Families of Flowering Plants: Descriptions, Illustrations, Identification, and Information Retrieval.’ Version: 19th August 1999. http://biodiversity.uno.edu/delta/.
10. Wheatley C.C. and W.W. Schwabe. 1985. Scopoletin involvement in post-harvest physiological deterioration of cassava root (Manihot esculenta Crantz). J. Exp. Bot 36:783-791.