Oil is contained within a range of oilseeds, fruits, nuts, and seed kernels. However, not all oil-bearing seeds and nuts contain edible oil. Some contain poisons or unpleasant flavors and are only used for paints. Castor oil needs very careful processing to make it safe and is not really suitable for small-scale processing. There is a universal demand for vegetable oils for household cooking, as an ingredient for other food products such as baked goods and snack foods, and as a raw material for the manufacture of soap, detergents, and body oils. Oil from crops such as maize is extracted using solvents that dissolve the oil. This method of extraction is not suitable for small-scale processors due to the high costs of equipment and the need for solvents that might not be readily available. Oil is contained in plant cells and is released when the cells are ruptured. The method of extracting the oil depends on the composition of the raw material. Some seeds are processed dry while palm fruits are processed wet. The process of oil extraction produces a by-product known as oilcake. This is very nutritious and can be used for animal feed or as an ingredient in other food products. During oil processing, the raw material (oil seeds or nuts) is heated to destroy any enzymes and micro-organisms that may cause rancidity. The oil may also be heated after extraction to remove as much water as possible which helps to increase the quality of the oil and the potential shelf life. Oils sho...