ABSTRACT
There is need for the hygienic processing of cassava prevalent conditions in the commercial grating areas of this staple food show a susceptibility to food contamination. A home scale cassava grater was improved on in a design and fabrication. Machine efficiency, safety factors, and portability were considered in this research. The grating hopper and clinte were modified using stainless steel sheet, the machine runs on single phase 6.5hp (horse power) diesel engine at a speed of 2600 rpm. The capacity of the grater fabricated was 150kg/hr.
CHAPTER ONE
- INTRODUCTION
Cassava originated from Latin America and was later introduced to Asia in the 17th century and to Africa in about 1558. cassava is one of the most important staple food crops grown in tropical Africa. It plays a major role in efforts to alleviate the African food crisis because of its efficient production of food energy, year round availability, tolerance to extreme stress conditions, and suitability the present farming and food systems in Africa.
In Nigeria, cassava is mostly grown on small farms, usually intercropped with vegetables, plantation crops, yams, sweet potatoes, melon, maize, etc. Cassava is propagated by 20-30cm long cutting of the wood stem, spacing between plant is usually 1-1.5meters. intercropping with bean, maize and other crops is practiced in young cassava plantations.
There are two common varieties of cassava, namely the bitter and sweet varieties. The cyanide content differs as well as suitability for different growing and consumption conditions. Usually, higher cyanide is correlated to high yield. Nigeria is the world largest producer of cassava tuber in the world, producing about 34 million tonnes of the world’s 174.0tonnes
Over the  past 25years significant market opportunities for cassava have opened up the animal feed industry, initially in the EEC (European Economic Community) countries but more recently for the rapidly expanding animal feed industries, of tropical developing countries. Cassava roots compete with other carbohydrate sources, especially maize and sorghum, on the basis of the price, nutritional value, quality and availability.
Cassava has several advantages compared with other carbohydrate sources especially other root crops. It has a high productivity under marginal climatic conditions which results in a low cost raw material. Root dry matter content is higher than other root crops at 35-.40%, giving optimum rates of 25:1 or better. Over 85% consists of highly digestible starch.
The potential disadvantages of cassava roots are their bulk and rapid perish ability, their low protein content, and the presence of cyanide in all root tissues, having about 70% moisture content.
Through simple processing the disadvantage of bulk and pershability can be overcome. A staple product is reached when moisture content falls below 14%. Natural drying is widely used to achieve this objectives drying also reduces moisure, volume and cyanide content of the roots. The dried cassava product thus has only one disadvantage with respect to other carbohydrate feed sources: low protein content which may be supplemented from other sources, particularly legumes.
For export market, where transportation over thousand of kilometers is necessary, further processing to produce high density pellets is carried out to minimize transport costs.
Presently, in Nigeria, the product of cassava usually locally consumed and exportation is limited because the products do not always meet the international standard for health foods. Thus, the need to encourage the small scale (home production) of cassava product to ensure quality of products and good hygienic values.
From the survey conducted, it was observed that most of the cassava grater in the research areas are usually corroding (reducing service life) due to the acidic nature of the cassava fluid and material used for the fabrication. To ensure all cassava products is free from any tastes, odor or infected by iron content of parts (food poisoning) which may affect the quality of their contents (FAO/GIEWS, 2001) hence need to modify the design and use appropriate material for fabrication.
Fresh cassava roots or tuber cannot be stored for long because they rot 3-4 days of harvest, hence need for processing follows immediately after harvesting.  Cassava processing leading to size reduction includes, peeling, grating dehydrating, sieving etc. In view of the above mentioned problems and the overall importance of the cassava products the following objectives are required to address the shortcoming of the grater.
The following research objectives needs to be accomplished:
- To design and fabricate model cassava grater.
- To modify the design of the existing cassava grater (dimensions) to the home use small scale size.
- To change the crude wooden hopper and chutes used in cassava grating machines to lasting stainless steel.
- To save time and cost of processing cassava products by the average family.
- To promote health consumption of cassava products
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