CHAPTER ONE
INTRODUCTION
1.1 Background of the Study
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).