EXTRACTION METHODS OF VOLATILE OILS

 

Extraction of volatile oils

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

Ø  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.

Ø  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.

There are three chief methods that come under this; they are enfleurage, maceration and a spraying process

Ø  Enfleurage:

 In this a fatty layer is prepared using lard and the flower petals are spreaded over it, after the imbibition 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.

 

Ø  Maceration:

 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.

Ø  Spraying or pneumatic process

 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.

ü  Soxhlet (hot continuous) extraction

In this method; the fine ground crude drug is placed in a porous bag (Thimble), which is placed in the chamber of the soxhlet extractor.

The extracting solvent in the flask is heated and its vapors condense in condenser.

The condensed drops of solvent fall in the porous bag (thimble), dissolving out the desired component from a solid mixture.

When the siphon tube fills to overflowing, it initiates a siphoning action into the flask. This process is continuous/repeated and is carried out until a drop of solvent from the siphon tube does not leave residue when evaporated.

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

ü  Supercritical fluid extraction

•       It is the process of separating one component (the extractant) from another (matrix) using supercritical fluids as the extracting solvents

•       The system must contain a pump for CO2, a pressure cell that contains the  sample ,a mean of maintaining pressure in the system and a collecting vessel

Ø  The liquid is pumped to heated zone, where it is heated to supercritical conditions

Ø  It then passed into extraction vessel. Here it diffuses in the solid matrix and dissolves the material to be extracted

Ø  The dissolved material is taken out from extraction vessel into a separator at low pressure