For plant materials with a low potential yield of oil (e.g. jasmine)
or others with a high percentage of resinous compounds (e.g. oakmoss)
extraction with volatile solvents may be the most appropriate method.
Solvent extraction tends to produce oils with a finer fragrance than
steam distillation, so it is much favoured in the perfumery industry.
Because it does not involve heat, there is less risk of damage to the
oil than in distillation. It is also more likely to extract the heavier
components. However not only the oil, but other constituents such as
waxes and plant dyes are extracted. The resultant oil can also be
contaminated with traces of the solvents used.
Solvent
Extraction: The plant material is soaked in a solvent such as
petroleum ether or hexane, which dissolves out the essential oil.
The mixture of solvent and oil is then passed into a distillation
vessel, where very gentle heat is applied - just enough to evaporate
off the solvent. The mixture of essential oil and other components
such as resins is known as a concrete. This concrete is then gently
warmed with some alcohol at a temperature just high enough to melt
it. The essential oil and a small proportion of the resins and waxes
will dissolve in the alcohol. The resulting alcoholic solution, or
tincture, then undergoes vacuum distillation. This removes the alcohol,
leaving an absolute. This method is often used for delicate oils
such as jasmine.
Enfleurage:
This method is typically used for delicate blossoms such as tuberose.
Petals are placed on a chassis, which consists of a wooden frame
containing a sheet of glass. A thin layer of fat is spread over
the glass. On several occasions the petals are replaced with fresh,
newly picked ones. Eventually the fat becomes saturated with essential
oil, forming a pomade. The pomade is then washed with alcohol and
an absolute formed, similarl to solvent extraction.........(click
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