1.0 Introduction
What Are Oils?
An oil belongs to a general organics group called “lipid”. It is a well-defined class of an organic substance which is an essential constituent of all forms of plants and animals. Oils are soluble in organic solvents such as ether but insoluble in water. Oil can be grouped into edible and non-edible depending on the amount of specified matters and impurities it contains. Owing to the fact that the used of oil as a raw material for the production of different useful products such as soap, margarine, etc. has increased tremendously, calls for the need for a seminar report on the extraction of oil from a local seed such as groundnut oil from its seed.
Nature of Extraction
This is defined as a technique in which a solute distributes itself between two immiscible solvents as a result of its different solubilities in the two solvents. It is the prefential solution of one or more constituents of a solid mixture by contact with a liquid solvent. This is a unit operation which is one of the oldest in the chemical industries. 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 summoned 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 occur. Crushing and grinding of such solids will greatly enhance the extraction action, because the soluble portion will now be make more accessible to the solvent.
Moreso, seeds like groundnut seeds are cellular in structures, and the natural products to be extract from this materials are usually found inside the cells of the seeds. If the cell walls remain intact upon exposure to a suitable solvent, the extraction will involve osmotic passage of the solute through the cell walls. This may be slow, but it is impractical and sometime undesirable to grind the material small enough to release the contents of individual cells.
Methods of Oil Extraction
There are three basic methods by which oil can be extracted from oil bearing seeds.
They include:
- Rending
- Mechanical expression
- Solvent extraction
Rendering
The crudest method of rendering oil from seed which is still practiced in some developing countries such as Nigeria involves heaping up the seeds in piles and exposing them to sun in order to collect the oil that exudes. This method is used in the preparation of seeds of high oil content such as olive and palm oils.
Mechanical Pressing
In this case, the walls of the seeds are broken by crushing, flaking, rolling, cooking or pressing under high pressure to liberate the oil. This method is utilized to recover the major portion of the oil from many seeds with high oil content.
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