CHAPTER ONE
1.INTRODUCTION
1.1 BACKGROUND
Cassava which is known biologically as “manihotesculentacrantz” is a crop which has many varieties. Cassava, is a perennial woody shrub in the Euphorbiaceous (Spurge family) native to South America, but now grown in tropical and sub-tropical areas worldwide for the edible starchy roots (tubers) which are a major food source in the developing world, in equatorial regions including Africa, South America, and Oceania. Also known has yucca, manioc, and tapioca.
It is a major food crop in Nigeria (kim, 2009). It supplies about 70% of the daily calorie of over 50 million people (Agbetoye, 1999) and about 500 million people in the world. It is a basic staple food to more than 70% of Nigerian population and it is consumed at least once every day (Njoku and muoneke, 2008). It was probably the emancipated slaves who introduced the cassava crop into southern Nigeria, as they returned to the country from South America via the Islands of Sao Tome and Fernando Po. At that time there was Portuguese colonies off Nigeria shores (Ekanem, 1962). Cassava, however, did not become important in the country until the end of the nineteenth century when processing techniques were introduced, as many more slaves returned home.The cassava root is long and tapered, with firm, homogenous flesh encased in a detachable rind, about 1mm thick, rough and brown on the outside. Commercial varieties can be 5cm to 10cm in diameter at the top and around 15cm to 30cm long (FAO, 2003).
The cultivation of the cassava crop is by the propagation of stem cuttings. Roots can be harvested between 6 months and 3 years after planting depending on the cassava variety. It is rich in carbohydrates, calcium, vitamin B and C, and essential minerals.
The roots are dug up from the soil, removed from the plant and washed before being processed.
Gari is a processed fermented product from cassava and is consumed in Nigeria as well as in most countries of the West African coast and in Brazil.
In sub-Saharan Africa (SSA), cassava is mainly a subsistence crop grown for food by small Scale farmers, who sell the surplus(IITA, 2003). It grows well in poor soils (IITA, 2011). Nigeria is currently thelargestproducerof cassava in the world with an annual production of over 34 metrictons (Mt) of tuberous roots (FAO, 2002).Gari is a widely consumed Nigerian food; an estimated 4.2 million tons were produced in 2009 (NBS 2010).
Cassava is largely consumed in many processed forms in Nigeria. Its use in the industry and livestock feed, is well known, but is gradually increasing, especially as import substitution becomes prominent in the industrial sector of the economy. As a cash crop, cassava generates cash income for the largest number of households in comparison with other staples (Adeniji, et al, 2011). Currently, quality of gari can be enhanced by adding few drops of palm oil. At the end of the frying operation, the product is still hot and a little bit damp. It is then allowed to cool and dry in a cool dry shade, until the moisture content is reduced to 12% (Gbasouzor, et al., 2012).
Earlier designs on gari production machines did not produce the desired and acceptable cassava product for the producers and consumers. The designs of these machines did not take into account the specifications of the existing local technology. It has been quite difficultto mechanize this operation correctly and rightly because this operation was not well understood by many designers and manufacturers. Some have erroneously assumed garification to be the same as dehydration while others had taken it to be roasting. Before the construction and development of ESUT (2015) model, a lot of research were carried out ranging from the village technique, improved traditional methods and mechanized methods designed by different research institutions, universities and companies. It was discovered that village technique gives the best quality gari. The question is how this village technique can be simulated and mechanized using the same method to achieve the same or better quality of the product.
ESUT (2015) model is a batch process like the village technique. It has an aluminum frying pan in place of cast iron pan used in village technique. A paddle is connected directly in the frying pan to an electric motor through a shaft to eliminate human hand used in stirring cassava mash in the village method.
The aluminum frying pan is used, because it disperses heat faster than the stainless steel and does not buckle under high temperature. There is a charcoal chamber at the bottomof the fryer thatis fed with charcoal used in frying the gari. The chamber is constructed using metal rods, each separated from each other by a distance of 20mm. The ashes from the burnt coal, falls to the bottom of the fryer.
The aluminum frying pan is located inside mild steel and the distance between the frying pan and mild steel is reinforced using fiberglass to prevent the escape of heat from the frying chamber. A blower of one horse power is used to blow/fan the charcoal chamber, to heat up the ignited charcoal and to avoid the nuisance of smoke. An exhaust pipe is connected to the charcoal chamber, to remove smoke from the charcoal chamber. The system has good electrical connections that sense the quantity of heat in use to the temperature gauge allows the operator to vary heat during frying and permits the machine to automatically turn off when there is excess current and load.
After frying, the discharge port is opened to allow the fried gari to leave the machine; another batch of cassava mash is introduced into the machine by the operator who monitors the entire process. These components are allcontained in a control box.
1.2 OBJECTIVE OF THE PROJECT
The main objective of this project is to design and construct a functional and cheap batch process gari frying machine
1.3 CONDITIONS NECESSARY
To achieve the above objectives, the following conditions must be met:
- Adequate agitation and processing in order to achieve uniform heat circulation.
- Ensure that the final product is cooked and dehydrated
- Avoidance of caking of the cassava mash.
1.4 SCOPE OF THE PROJECT
The garification process (gari frying), is not a straight forward drying process (Igbeka, 1995). The product is first cooked with the moisture in it and then dehydrated. The sieved cassava grit is spread thinly in the pan 3-5kg per batch, the paddle helps to stir the gari constantly to prevent the food produce from getting burnt, until frying is complete, when it reaches a temperature of 80 to 85oC, the rapid heating partially gelatinize the gari, which is dried during the operation of frying; the moisture content of dewatered and sieved cassava mash is between 40 to 45% which has to be reduced to 10-12% moisture content in a time of 15 minutes.
A mechanical “garifier” or a mechanized system of frying and drying, usually takes the form of an aluminum drum or trough, paddles fixed to a steel shaft and rotating on the axis of the drum, the rotating paddles sweep the gelatinizing mesh from the trough wall to prevent sticking and burning and at the same time to move the material through the chamber to the discharge port, or outlet.
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