The grinding of grain occurs by the application of mechanical forces that alter the structure of the grain by overcoming the interior binding forces, after which the state of the solid is changed to flour. Grain produce on the farm is processed in some form before it is actually consumed. One of the important processes involving a non-chemical change to the fullest extent is that of reducing the harvested grain to flour. Traditionally, and in some parts of the world to this day, milling is accomplished by grinding the grain between two stones. The grinding stone consists of a lower stationary one, called the Quern stone and an upper stone which is mobile and called the hand stone. The oldest known flour milling devices are saddle stones (Williams and Rosentrater, 2007). A saddle stone is a cradle-shaped piece of hard stone which holds the grain. The hand stone can either be a cylindrical piece of stone (held in both hands and drawn across the grain rather like a rolling pin) or a disc with a vertical handle on its back (rather like an upside-down mushroom) held in one hand. These hand stones were used to crush the grain and produce coarse flour (Thomas and Filippov 1999). In order to make grinding easier, the grain is normally malted. Malting refers to the process whereby cereal grain is made to germinate by soaking in water and then have the germination halted by drying in hot air. Obviously, such method is both laborious and time consuming. In addition, it produces only enough ground or cracked grain for a household or extended family.
According to Culpin (1992), grinding of grains has been practiced since very early times when a device resembling a pestle and a mortar was employed in the production of meal for human consumption. The first mills were modifications of this device, in which a grain was put through an opening in a disc-shaped stone which was caused to rotate upon another. The gradual development of this type of mills during thousands of years has led to the evolution of the burr stone mill. The earliest records of food production in Africa show that indigenous grains have long been milled to produce coarse flour for cooking. Traditional crops such as sorghum, millet and maize have been ground for centuries either with a crude mortar and pestle fashioned from a tree stump and branch or by using flat stones or rubbing stones. All these types of grinding systems are still in common use throughout Africa today.
Brain and Rottger (2006) reported that in the mid-nineteenth century, electric motors were invented and higher speed machines, such as hammer and plate mills, began to replace traditional stone grinders. A relatively low-speed, water-cooled diesel engine can, for example, power a hammer mill, producing maize flour of acceptable quality. These mills are in widespread use in rural parts of the world in areas where no electricity grid is available. Diesel-powered grain mills are limited to areas with access to fuel and spare parts. Many people still cannot afford paying for commercial grain-grinding services and they grind by hand using traditional techniques. Therefore, pounding is a common sight and sound in many areas. It is often a social activity, carried out predominantly by women, and many hours are spent each day in this laborious and time-consuming task. The pestle may weigh up to 4 kg, and pounding requires a lot of effort (FAO, 1983).
For several decades, men were faced with challenges of particles being grinded alongside with grains with the available grinders, however, the grinded products were unknowingly consumes by the consumers and thereby cause series of illness in the human system. Globally, moving away from traditional foods to more refined Western diets has been linked to increases in the prevalence of chronic non-communicable diseases (Suleyman, 2014) of which over the years, the means to overcome this challenge has been searching for. Most developing countries like Nigeria experience high mortality rate and this is exacerbated by poor health delivery and inadequate monitoring of foodstuffs which results in high intake of unwholesome food. High level of trace metals in food is a potential source of disease when consumed by humans and constant monitoring of foodstuff for trace metal contamination is crucial for the health of the citizenry due to the various diseases they induce. Unhygienic grinding of grains for foodstuff with old and worn out grinding machines is the usual practice in Nigerian markets and the operators do not appreciate the health risks involved in their operations (Jude and Prosper, 2016).
Heavy metals disrupt basic metabolic functions in two ways: on one hand, they disrupt the functioning of vital organs and glands such as the heart, brain, kidney, bone or liver, on the other hand, they move nutrients that are essential minerals and prevent them from fulfilling their biological functions. For example, aluminum as a chelator has the ability to capture and prevent the uptake of essential elements such as calcium, zinc and copper, and disrupt the proper use of many of them (Dabonne et al, 2010). This metal is heavily involved in the onset of Alzheimer's disease. It is responsible for the alteration of neurons (Miu and Beng, 2006; Bharathi et al., 2008). Depending on the heavy metal in question, toxicity can occur at levels just above naturally occurring background levels, meaning that consumption of foods with a high heavy metal concentration can cause acute or chronic poisoning (Llobet et al, 2003). Poisoning can result in damaged or reduced mental and central nervous function, as well as damage to blood composition, lungs, kidneys, liver, and other vital organs. Long-term exposure to heavy metals may result in slowly progressing physical, muscular, and neurological degenerative conditions as well as cancer (Llobet et al, 2003). A domestic grain grinding machine is equipment used for grinding maize, beans, melon, millet and such other food crops. This equipment comprises essentially of an electric motor, belt, pulley, transmission shaft, hopper, mills, spiral conveyor and stands. These alleviate the rigors and problems we encounter when grinding grains for the foodstuff. A domestic grain grinding machine is a domestic grinder that is used to grind various grains of any form without the usual metallic or heavy particles being eating by human being.
Grinding of grains is one of the oldest cultural techniques of humanity. All civilizations that feed more or less exclusively from cereals were forced to develop technology for grinding grain crops. In all traditional civilizations, grinding is the domain of women. There are two different techniques used in effecting size reduction of grains. The grinding done by pounding the grains (mortar and pestle) and the grinding done by crushing the grains between two stones (grinding stone). The method of pestle and mortar is the widely used in the West-African country. The use of grinding machine is one of the simplest methods of processing grains alternative to the traditional methods of grain processing using stone, mortar and pestle. However, machines constructed using metal plates results in tearing and wearing away of the materials of construction. The effect of this is the contamination of the processed foodstuff. This is known to have negative health implications when accumulated and consumed in large quantities. Another problem is that the pounding work using mortar and pestle is demanding and tiring and the used of grinding stone is very laborious. Based on this backdrop, the study sought to design and construct a local fabricated grain grinding machine using available local technology.
The objectives of the study are;
i. To construct grain grinding machine with local materials.
ii. To construct a machine that can perform domestic operations.
iii. To produce a grain grinding machine that is lesser in vibration, weight and in size.
i. This is to promote indigenous machine and their producers.
ii. To have a portable grain grinding machine constructed for domestic uses with a powered driven source.
iii. To improve the economic and the country as a whole by neglecting imported blenders i.e producing machine that is affordable to substitute the imported blenders.
iv. To be able to meet National Board for Technical Education (NBTE) requirement in awarding National Diploma (ND) in Mechanical Engineering.
1.5 Scope/Limitations of the Study
This study is on design and construction of grain grinding machine. The study will focus on construction of a local fabricated grain grinding machine using available local technology.
Limitations of study
Financial constraint: Insufficient fund tends to impede the efficiency of the researcher in sourcing for the relevant materials, literature or information and in the process of data collection (internet, questionnaire and interview).
Time constraint: The researcher will simultaneously engage in this study with other academic work. This consequently will cut down on the time devoted for the research work.