Volatile oils are prepared by means of several techniques and those techniques are discussed here
EXTRACTION OF VOLATILE OILS
Volatile oils are prepared by means of several techniques
and those techniques are discussed below:
Extraction by Distillation
The distillation is carried out either by water or steam.
The volatile oils from fresh materials are separated by hydrodistillation, and
volatile oils from air dried parts are separated by steam distillation. However
it is better to use fresh materials in either case.
Extraction by Scarification
This method is used for the preparation of oil of lemon, oil
of orange, and oil of bergamot. These oils are found in large oil glands just
below the surface in the peel of the fruit. The two principal methods of
scarification are the sponge and the ecuelle method.
a. Sponge Process: In this process the contents of the
fruit are removed after making longitudinal
or transverse cut, and the peel is been immersed in water for a short period of
time. Then it is ready for expression. The operator takes a sponge in one hand
and with the other presses the softener peel against the sponge, so that the
oil glands burst open and the sponge absorbs the exuded oil, which is
transferred to a collecting vessel. The turbid liquid consisting of oil and
water is allowed to stand for a short time, whereupon the oil separates from
water and is collected. The whole of the above process is carried out in cool,
darkened rooms to minimize the harmful effects of heat and light on the oil.
b. Ecuelle Process: In this process, the rinds are
ruptured mechanically using numerous
pointed projections with a rotary movement and the oil is collected.
Extraction by Non-Volatile Solvent
A nonvolatile solvent, for example, a fine quality of either
lard or olive oil, is used in this process. After saturation with the floral
oil the lard or olive oil is sometimes used as a flavouring base for the
preparation of pomades, brilliantine, etc., or converted to a triple extract.
In the latter instance the lard or oil is agitated with two or three successive
portions of alcohol, which dissolve the odorous substances. The mixed
alcoholic solutions so obtained constitute the ‘triple extract’ of commerce.
There are three chief methods that come under this; they are
enfleurage, maceration and a spraying process.
1.
Enfleurage: In this a fatty layer is prepared
using lard and the flower petals are
spreaded over it, after the imbibitions is over the fatty layer is replaced
with fresh petals. After the saturation of fatty layer the odorous principles
are removed by treating with alcohol and a triple extract then prepared. When
oil is used as a solvent the flowers are placed on an oil-soaked cloth
supported by a metal grid enclosed in a frame. Fresh flowers are added as
required, and finally the oil is expressed from the cloths. It may then be used
as perfumed oil, or extracted with alcohol to produce a triple extract.
2.
Maceration: This is also used to extract the
volatile matters of flowers. The lard
or oil is heated over a water bath, a charge of flowers added and the mixture
stirred continuously for some time. The exhausted flowers are removed, pressed,
the expressed fluid returned to the hot fat, fresh flowers, added and the
process continued until defined weights of flowers and solvent have been used.
Again, a triple extract is prepared by extracting the perfumed lard or oil with
alcohol.
3. Spraying:
In this process a current of warm
air is sprayed through a column of
the flowers. Then oil or melted fat is sprayed over this oil-laden air which
absorbs and dissolves most of the perfume, the collected oil or fat is then
extracted with alcohol as described above.
Extraction by Volatile Solvent
In this the flowers are extracted by using the solvent light
petroleum and the latter is distilled off at a low temperature, leaving behind
the volatile oil.
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