INTRODUCTION
Oil (Essential Oil) is concentrated, hydrophobic liquid containing volatile aroma compounds from plant. The essential oil are also known as volatile oils, ethernal oils or aetherolear, or simply as the oil of the plant from which they were extracted, such as oil clove. An oil is “essential” in the sense that it carries a distinctive scent, or essence of the plant. Essential oil as a group do not have any specific chemical or pharmaceutical properties in common, instead they are defined by the fact that they convey characteristics fragments. The oil constituents is a well defined class of neutral organic substance, which are essential constitutants of all forms of plants and animal. The oil can be grouped into edible and non-edible depending on the amount of unspecified matter and impurities. Essential oil are generally extracted by distillation. Other process include expression, or solvent extraction. They are need in soap, perfumes, cosmestics, and other products, for flavoring food and drink, and for scenting incense and household cleaning products. The only possible way of obtaining large quantity of oil from local seed being vegetable or plant material is by extraction and could bet be achieved by leaching.
Extraction other wise called leachingis the preferential solution of one or more constituent of a solid mixture by contact with a liquid solvent. It is a unit operation in the chemical industries that have been given many names, depending to some extent upon the techniques used for carrying it out.
Extraction of oil from a local seeds (Groundnut seed) can be carried out using any of the two solid liquid extraction methods namely: mechanical extraction methods or the use of solvent otherwise called mass transfer method. The yield of the second method is higher but contain more impurities than the first method and it requires another unit operation (distillation) for purity. The success of an extraction and the technique to be used will vary frequently depending upon any prior treatment which may be given to the solid. In some instance small particles of the soluble material are completely surrounded by a matrix of insoluble matter. The solvent must then diffuse into the mass and the resulting solution must diffuse out before a separation can result. Crushing and grinding of such solids will greatly alliterate the leaching action, since then soluble portion are made accessible to the solvent. Seeds like groundnuts seeds and other vegetable seeds are cellular in structure, and the natural products to be leached out from this material are usually found inside the cell.
Solvent extraction plant uses hexanes as a solvent to extract oil from oil seed cake. These plants are expensive and only suitable for large volumes which justify capital cost of equipment. Where large amount of oil seed are available, solvent extraction becomes a commercially viable option to extract the residual oil left in the cake and leave an almost oil free powder know as oil seed meal. Both cake and meal are incorporated in animal feeds.
The types of solvent available for leaching include n-hexane, benzene, ethyl either etc which are high petroleum fractions. The choice of a solvent for extraction of oil is a function of its volatility and relative volatility for easy separation by distillation.
Extraction (solid-liquid or leaching) differs very little from the washing of filtered solids. And leaching equipment strongly resembles the washing section of various filter. In leaching the amount of soluble materials removed is often greater than in ordinary filteration, washing and the properties of the solid may change considerably during the leaching operation.
METHOD OF OIL EXTRACTION
Extraction Method Include:
MANUAL PRESSES METHOD
Oil can be extracted by pressing softer oil seed and nuts, such as groundnuts and shear nuts, whereas harder, more fibrous material such as copra and sunflower seed can be processed using ghains. Pulped or ground material is loaded into a manual or hydraulic press to squeeze out the oil water emulsion. This is more efficient at removing oil than traditional hand squeezing, allowing higher product rates.