CASSAVA

Starch is obtained when the roots are peeled,washed and finely grated. The starch is filtered from the fibre andthen collected either by sedimentation or centrifugation, dried andmilled into fine powder. Starch is used in textiles, foods such asbread, and in the fructose syrup industry. Cassava starch is asubstrate for dextrins used in the manufacture of glues. Cassava flouris used as an adjunct in the beer-brewing industry. Cassava alcohol isdistilled after the alcoholic fermentation of cassava. The use ofbacterial acetic acid (Acetobacter spp.) in the fermentationof boiled ground cassava after fermenting with starter rice yeast andcellulase enzyme leads to the production of cassava vinegar.

Industrialproducts such as starch, glues, cassava beer, cassava alcohol andcassava vinegar are obtained from various processing operations usingcassava.

Chikwangue: Thecassava is soaked in water for several days until it softens; the rootis then peeled, macerated and sieved to remove fibres. The paste ordough is wrapped in banana leaves and eaten usually after boiling.

Fufu: Theroot is peeled (sometimes after soaking in water) and boiled orsteamed, followed by pounding with a pestle in a mortar into fufu, which is eaten with a soup containing fish, meat and/or vegetables.

Gari: Roots are peeled,washed and grated. The mash is placed in bags and squeezed (either bytying it up with sticks and continuously tightening the ropes or by avariety of screw or hydraulic presses) for a minimum of 48 hours toallow detoxification by fermentation. The dough is fried dry and storedin bags and sealed plastic packages, to be rehydrated and eaten withsoups, sauces, and sometimes sugar.

Fermentation is another important process inmaking cassava products. The importance of the fermentation stage incassava processing is linked to the reduction of cyanogenic glucosides,the introduction of flavours and the lowering of the pH in thefermented product.

Dryingof cassava roots is an important step in reducing weight and microbialspoilage. The chips are spread on mats, cement floors and roofs ofhouses to sun-dry. After that they are milled by pounding with a pestlein a wooden mortar or by using a grindstone, followed by sievingthrough a screen. Mechanical mills are also used sometimes forefficiency.

Cassavaroots are rich in energy and contain mainly starch and some solublecarbohydrates, although poor in protein. It has been estimated thatpeople eat more than 60% of all cassava produced, and about a third ofthe harvest is fed to animals, while the rest is transformed intosecondary products. It can be processed into gari (West Africa) , fufu (Ghana) , chikwangue (Central Africa), flour for bread, etc.

Utilisation and Processing

Raw cassava contains cyanogenic glucosides, particularly linamarin andlotaustralin, which are converted to prussic acid (hydrogen cyanide,HCN) when they come in contact with linamarase, an enzyme that isreleased when the cells of cassava roots are ruptured. Good processingand cooking methods reduce the cyanide levels, and acute cyanidetoxicity rarely occurs. Chronic cyanide toxicity occurs when cassavaconsumption is very high (7 kg or more of fresh roots per day over longperiods), especially where iodine and/or protein consumption is verylow.
 

Raw cassava contains cyanogenic glucosides, particularly linamarin and lotaustralin, which are converted to prussic acid (hydrog