Cassava
Cassava Root Yard Cassava harvest

Florence Nwanzuruahu Nkiru Nwapa
Florence Nwanzuruahu Nkiru Nwapa, Nigerian novelist (1931-1993).

We thank the almighty God
For giving us cassava
We hail thee cassava
The great cassava

You grow in poor soils
You grow in rich soils
You grow in gardens
You grow in farms

You are easy to grow
Children can plant you
Women can plant you
Everybody can plant you

We must sing for you
Great cassava, we must sing
We must not forget
Thee, the great one

[by Flora Nwap ]

Cassava - common name for any of several related plants native to tropical regions in the Americas. Cassava is the West Indian name; manioc, or mandioc, is the Brazilian name; and juca, or yucca, is used in other parts of South America. The plant grows in a bushy form, up to 2.4 m (8 ft) tall, with greenish-yellow flowers. The roots are up to 8 cm (3 in) thick and 91 cm (36 in) long. The roots contain from 20 to 32% of starch at maturity. Early maturing cultivars are ready for harvest after 8-12 month.

Two varieties of the cassava are of economic value: the bitter, or poisonous; and the sweet, or non-poisonous. Because the volatile poison can be destroyed by heat in the process of preparation, both varieties yield a wholesome food. Cassava is the chief source of tapioca, and in South America a sauce and an intoxicating beverage are prepared from the juice.

The root in powder form is used to prepare farinha, a meal used to make thin cakes sometimes called cassava bread. The starch of cassava yields a product called Brazilian arrowroot. In Florida, where sweet cassava is grown, the roots are eaten as food, fed to stock, or used in the manufacture of starch and glucose. In Africa Gari is a popular food preparation. Tapioca, easily digested starchy foodstuff extracted from the root of the cassava plant. Tapioca is often used in pudding. The term "tapioca" is used to designate products made from cassava like starch, dried chips etc. Tapioca is also replacing mung bean starch - the prime material for making clear starch noodles, however, tapioca starch need modification to produce a gel with the same strenght as mung bean starch, which is very high in amylose.

Scientific classification: Cassavas belong to the family Euphorbiaceae. Both bitter and sweet cassava are classified as Manihot esculenta or Manihot utilissima or Manihot Aipi

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Tapioca starch
(Amylum Manihot)

Chips. This is the most common form in which dried cassava roots are marketed and most exporting countries produce them. The chips are dried irregular slices of roots which vary in size but should not exceed 5 cm in length, so that they can be stored in silos. They are produced extensively in Thailand, Malaysia, Indonesia and some parts of Africa.

Process. The present method of processing chips is very simple, consisting in mechanically slicing the cassava roots and then sun drying the slices until their moisture content is only 14 per cent: dry chips can be stored longer and are cheaper to transport. The recovery rate of chips from roots is about 20-40 percent. When the roots are not sorted, peeled and washed, the chips are usually brown in colour and have a high content of fibre sand and foreign objects as well as hydrocyanic acid. Trimming, peeling and washing the roots in a similar manner as for the processing of cassava flour are recommended in order to produce white chips of superior quality. The roots are shredded in a special machine, which is usually made locally. The machine consists of a rotating notched cutting disk or knife blades mounted on a wooden frame equipped with a hopper.The cassava roots are cut into thin slices and pieces as they pass through the machine. A chipping-machine can do in one hour the work that used to take three days by hand.

Drying. Sun drying is used mostly where the sliced roots are spread out on drying areas, or concrete floors of various dimensions. The concentration of chips during drying should not exceed 10-15 kg/m2, the required drying area space being about 250 m2

 for each ton per day of dried roots produced. To produce good quality chips the roots must be sliced and dried as quickly as possible after harvest. The chips should be turned twice a day during the drying period, usually two or three sunny days, until the moisture content reaches 13 - 15 percent. At the risk of rain the chips are piled up and spread out again when the burst is over.The chips are considered dry when they are easily broken but too hard to be crumbled by hand. The thickness of the slices also has an effect on the quality of chips. Thick slices may appear dry on the surface when their internal moisture content is still high. When rain threatens during the drying process, the chips are collected by hand or by a tractor into piles under a small roof. Interrupted sun drying affects the quality of the finished chips and pellets. When the semidried chips are wet again by rain, they become soggy and upon completion of drying lose their firm texture. In rainy regions, where continuous sun drying is difficult, some form of artificial heat drying is required.

Pest. Whitefly (Mealy bugs) control is difficult and complex as whiteflies rapidly gain resistance to chemical pesticides. 2010 a serious attack ruined large crops in Thailand. The USDA recommends "an integrated program that focuses on prevention and relies on cultural and biological control methods when possible. Most effective is to observe the fields every day and remove all plants inculsive the infested plants in a rather larger area. Thai Tapioca Development Institute has succeeded to develop an effective biological method based on the Anagyrus lopezi wasp imported from IITA, Benin. The mealybug injects a toxin into the cassava plant while feeding on its leaves and stems, causing the plants to wither and die. The parasitic  wasp known as Anagyrus lopezi can be introduced into the infected areas. The wasp lays its eggs in the mealybug and the growing larvae eat their way out, effectively killing the host.

Broken Roots. . Similar to chips in appearance, but generally thicker and longer, they are often 12-15 cm long and can jam the mechanism of handling equipment.

Pellets. The pellets are obtained from dried and broken roots by grinding and hardening into a cylindrical shape. The cylinders are about 2-3 cm long and about 0.4-0.8 cm in diameter and are uniform in appearance and texture. The production of pelleted chips has recently been increasing as they meet a ready demand on the European markets. They have the following advantages over chips: quality is more uniform; they occupy 25-30 percent less space than chips, thus reducing the cost of transport and storage; handling charges for loading and unloading are also cheaper; they usually reach their destination sound and undamaged, while a great part of a cargo of sliced chips is damaged in long-distance shipment because of sweating and heating. Pellets are produced by feeding dried chips into the pelleting machine, after which they are screened and bagged for export. The powdered chips which fall down during pelleting are re-pressed into pellets and the process is repeated. There is usually about 2-3 percent loss of weight during the process.

Meal. This product is the powdered residue of the chips and roots after processing to extract edible starch. It is generally inferior in quality to chips, pellets and broken roots, has a lower starch content and usually contains more sand. Meal perform badly in the transport system of a modern feed mill.

Wheat Bread with Cassava FlourFlour. Tests in our laboratory proved that cassava starch and high quality cassava flour can act as a wheat flour extender with no harm to palatability and taste. We also developed the process for manufacturing this high quality flour from fresh cassava roots.

Pulp. During the processing of cassava starch, the residual pulp which is separated from the starch in the screening process is used as an animal feed. It is usually utilized wet drip-dry with 12-15% dry matter in the neighbourhood of the processing factory but is sometimes sun dried before it is sold. With efficient extraction the starch content is quite low and this pulp is be utilised by ruminant only.

Food Application. Starch is an important constituent in many foods. It plays an obvious role in achieving the desired viscosity in such products as cornstarch pudding, sauces, pie fillings and gravies. It plays a more subtle role in potatoes, cereals, and baked products such as biscuits, muffins, popovers, pastry, cake and bread. It is used as a water binding and texturizing agent. It has a high viscosity, water-holding capacity and binding abilities.

Cassava starch is a white to off-white powder with a moisture below 13%. The pH of a slurry in water is neutral. Cassava / Tapioca Starch is very bland and clean in flavor and is not masking the flavours used.

Cooked it forms a quite clear gel with a long and slightly stringy texture. Upon cooling, it sets to a soft gel. It loses most of its thickening ability during prolonged heating and under acidic conditions. The cooked gel resambles that of potato, but the texture is less stringy and the flavor i more neutral, making it a preferred thickener in delicate foods and desserts.

Special food applications: Extruded snacks, where it improves expansion, custard-type pie filling, where it reduces surface cracking and in baby foods as a bodying agent. In biscuits and in cream sandwiches 5-10 % tapioca starch softens the texture and renders the biscuit nonsticky.

In general it may be used as a thickener in foods not subject to rigorous processing.

For household cooking tapioca starch is the starch of choise in thickening fruit desserts - it gives a clear dessert but with improved and "shorter" texture compared to potato starch.

Waxy Tapioca. CIAT (Center Internacional de Agricultura Tropical), Colombia initiated a program to develop the waxy tapioca using conventional plant breeding methods that include germplasm collection, crossbreeding and selection. CIAT started the tapioca breeding program in March 2006, inducing the mutants by selfcrossing the selected genotypes, and successfully derived 2 mutants that posses unprecedented traits. One was the waxy or amylose-free. Another, just the opposite, had twice as much amylose content as regular tapioca. Both traits have significant commercial value. Waxy, 100% amylopectin, is used in many applications in foods and cosmetics that require high paste stability or low retrogradation. On the other hand, High-amylose is processed into resistant starches which are used in some other applications especially those related to health. It is of interest to have these traits present in tapioca.

Composition of Roots. Typical Composition of Mature Cassava Roots

Constituent %

Moisture

69.8

Starch

22.0

Sugars

5.1

Protein

1.1

Fats

0.4

Fibre

1.1

Ash

0.5

Brabender Viscogram

Brabender Viscogram