Cassava (Manihot esculenta crantz) is a major food crop in Nigeria, supplying about 70% of the daily calorie of over 50million people in Nigeria (Oluwole et al., 2004). At 93 million tons, cassava accounted for the largest share of root crop consumed as food in Tropical Africa in 1996 (Scott et al., 2000). It has also been estimated that cassava provides food for over 500million people in the world (Abu et al., 2006). Edible part of fresh cassava root contains 32-35% carbohydrate, 2-3% protein, 75-80% moisture, 0.1% fat, 1.0% fiber and 0.70-2.50% -Ash (Oluwole et al., 2004) .
A wide variety of foods are produced from cassava by fermentation, viz Garri, Fufu, Lafun, Attieke, Farinha de rnadioca, to mention a few (Adesina, 2001).
Cassava plants are of two (2) varieties namely; sweet cassava (Manihot utilisima) also known as the oko-yawo variety and bitter cassava (Manihot Palmata). Both variety are known to contain cyanogenic glycosides. The two major cyanogenic glycosides: linamarin and lotaustralin are hydrolysed to produce hydrocyanic or prussic acid (HCN) a poison, when it comes in to contact with the enzyme linamarase, which is released when the cells of cassava roots are ruptured (Marcus and Adesina, 2001). The principal cyanogenic glucoside is linamarin (95% of the total) while the remainder is lotaustralin. It was observed that the roots rapidly develop toxicity after grinding unless the pulp is heated immediately. (Adesina, 2001). Therefore, all forms of cassava processing decreases levels of cyanogenic glycoside and prussic acid in the final product (Marcus and Adesina, 2001).
Garri is a product, obtained by fermenting peeled, washed and grated fresh cassava roots (for about 72 hours), dewatering and toasting (Ekwu and Ugwuona 2007). In Nigeria up to 70% of harvested cassava roots are processed into garri. Garri is normally consumed by adding water and sugar to taste and eaten as a refreshing snack drink or by pouring sufficient quantities in hot water to obtain a stiffen pudden (eba) (Onabolu et al, 2002,) which may be eaten with soup or stew. Garri is usually processed using manual processing method and mechanical processing method.
Manual processing method involves the following distinct steps: peeling, grating, pressing and fermenting for 48-72 hours, sieving, toasting and separation into various particle sizes.
Mechanical processing method involves washing peeling, grating pressing, sieving, toasting and receiving without the involvement of manual operation. The liquor from the previous fermentation is used as a starter thereby reducing the fermentation period to about 6-8hours. The heating of the cassava during processing was presumed to inactivate linamarase and prevent the release of cyanide as linamarase decomposes at 72′% (Ekwu and Ehirim, 2008).
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(Author: Nwabueze Peter Okolie, Memunat N Brai, Oluwaseun M. Atotebi