Extraction is the process by which the purity of an oil is determined. Different methods of extraction are given below:

• This extraction method is simple and extensively used to produce a good quality essential oil.

• In this method, steam is used to release the essential oils from the plant material and then cooled and condensed to a liquid. 

• The oily layer floats on top and is skimmed off.

• This extraction process can be done by two methods, namely Select and Total.

• In Select method, the temperature of extraction is around 87.8°F (31°C).

• In this method, compressed CO2 gas is passed through the plant material which converts components into solution. When the process is completed the pressure is lowered, and the extracted components precipitate out.

• The same gas is recompressed and recycled for further use.

• In the Total extraction method, the plant material is processed at a higher temperature. The oil extracted by this method is rich in components than the Select method.

• The essential oils produced by this method are more expensive since the CO2 process equipment is extremely costly.

• Seeds, nuts, vegetables, fruits, and fruit peels are pressed at low heat.

• This is an excellent method to produce a quality oil.

• However, large amounts of these oils are usually refined afterwards using high heat and harsh chemicals. Therefore, it is important to check the label on the container in order to ensure that the oil is unrefined so that it contains all the valuable nutrients.

Oil absorbs the essence from the flowers soaked in hot oil after rupturing their cells.

Solvents like hexane and other toxic chemicals are used to extract the oils from plants. This method although efficient cannot be used due to the presence of toxic residues in the oil.

Expression
This process is used to extract essential oil from citrus fruits. The rind of the fruit is crushed to release the essential oil just under the surface.

The refining of extracted oil is carried out by using these steps:

In this, chlorophyll, vitamins, and minerals are removed.

The oil is bleached by adding Fuller’s earth and then filtering it to remove nutritive substances. The oil becomes clear in this step.

Using steam distillation for 30 – 60 minutes at high temperatures 450°F (232°C), the oil is deodorized.

This is the last process which prevents the oil from becoming cloudy during cold temperatures. What remains after filtering is nutrient-deficient oil with only fatty acids.