The term "essential oil" is generally applied to all aromatic products such as essence oils, absolutes, resinoids, and concretes. To get essential oils the aromatic essence molecules of the plant must be captured by technical extraction methods. Essential oils are liquids stored in various places in plants, that can be removed from the plant using extraction methods such as steam distillation, cold pressing, chemicals, or fat-absorption.
Essential oils can be extracted using a variety of methods as mentioned above, although some are not commonly used today. Presently, the most popular method for extraction is steam distillation and the majority of essential oils used in aromatherapy are distilled in this way, but as technology is advancing, more efficient and economical methods are being developed.
The extraction of an oil require large quantity of plant material and the method used to extract the oil is time consuming so requires a high degree of skill and care.
Hence, pure essential oils are expensive, but they are also highly effective - only a few drops at a time are required to achieve the desired effect.
Essential oils are usually liquid, but can also be solid, like orris root or semi-solid according to temperature, like the rose. They dissolve in pure alcohol, fats and oils but not in water.
Some of the important methods of extraction are discussed below :
In this, water is heated to produce water vapour, which carries the volatile chemical of the aromatic material with it. The water vapour is then condensed using a condenser and the resulting distillate is collected. The essential oil will normally float on top of the hydrosol (the distilled water component) and is separated out.
- Water Distillation
- Steam Distillation
- Hydro Diffusion
- Fractional Distillation
This method is used to extract citrus essential oils. It is basically a cold pressed method of extraction.
In this extraction method, solvents are used to extract the essential oils from the botanical material.