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 The
extraction of oil from good quality raw material like
Rice Bran, Soyabean, Mustard Cake etc. is a complicated
process comprising of preparatory section, Extraction
Section, Conditioning Section, Distillation Section and
Recuperation Section. The by-products i.e. De-oiled Cakes
is an excellent ingredient for cattle and poultry feed
manufacturing, since, De-oiled Cake contains proteins
and other nutrients.
Moreover there is a large domestic and export market for
De-oiled Cakes. The Solvent Extraction process is more
efficient than the traditional kolhu, hydraulic press,
ghani or continuous screw process, since only 0.7% or
less is left as a residual in this process. Solvent extraction
is essentially a process of diffusion of solvent into
oil bearing cells of the material to be extracted resulting
in a solution of the oil into solvent. For a successful
and efficient extraction, it is therefore, necessary to
ensure that each and every cell is brought in contact
with the solvent.
After the oil is extracted from oilseeds by mechanical
means, percentage of oil normally retained in the cakes
is about 7-9% and it is not possible to further extract
the oil economically  by
mechanical means. If further extraction (by mechanical
means) is attempted, the quality of oil goes down and
also it is very uneconomical too. The only method possible
to extract the oil from cakes is by solvent extraction
process. The solvent extraction is essentially a process
of diffusion of the solvent into oil bearing material
as well as into the material to be extracted resulting
in a solution of oil in the solvent.
For successful and efficient extraction, it is therefore
necessary to ensure that each and every oil cell is brought
into contact with the solvent. For this purpose two conditions
are to be fulfilled:-
| • The raw material
should be prepared to make it easy for the solvent
penetrate the oil cell and |
| • The solvent is
spread over uniformly. Whereas the mechanical expulsion
with expellers submits the oil to high temperature
and pressure, which causes hydrolysis and colour
fixation of oil, the continuous solvent extraction,
on the other hand, does not cause any harm to the
oil which is recovered with the same characteristics
as were present in the oil bearing material. |
Indeed, the outstanding and rich advantages of continuous
solvent extraction are such that it has become and viable
factor in determining the survival of the vegetable oil
industry in many parts of the world.
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