There are many methods of essential oil extraction, the most popular being steam distillation. Other methods include expression, enfleurage, maceration, and solvent extraction.
Essential oils are extracted from many different parts of their plants. For example, Lavender is extracted from its flowers, Orange from the rind of its fruit, Frankincense from the resin of its tree, Cinnamon from its bark, Pine from its needles, and so on.
Depending on the method of extraction and the quantity of the raw materials used, the price and quality of the oil are determined. As an example, it takes roughly 12,000 Rose blossoms to produce 5 ml of Rose. Whereas it take 100 kilos of Lavender leaves to produce 3 liters of Lavender. As a result Rose is roughly 24 times more expensive than Lavender.
There are many other factors to be taken into consideration when producing a good quality essential oil, which is important for its full benefit. Soil quality, climatic and geographic conditions all contribute to the overall quality of the essential oil.
In some cases the length of cultivation is most important. Jasmine flowers must be picked by hand at dawn on the very first day they open. A Sandalwood tree must be 30 years old and 30 feet high before it is ready to produce its best quality oil.
As mentioned earlier, distillation is by far the most popular method for essential oil extraction. This is mostly used for leaves, flowers, seeds, roots, and stems.
Stills are believed to date back to the eighth century where they were used by the Arabs. Many diverse methods have been used since, the best method is using a 'low-pressure' still which produces the best quality essential oil for aromatherapy purposes.
Two large containers are used. The first container has an inlet at the bottom, in which steamed water, heated at low pressure, is sent in. This container is loaded with the aromatic raw materials (the part of the plant to be distilled). The steam rises, gently simmering the contents.
The heat causes the essential oils to be released from the plant by evaporation and to travel, as part of the steam, towards an outlet at the top of the container. This outlet carries on into another container and coils itself all the way down. This coil is called a serpentine.
The second large container is filled with cold water and the serpentine is immersed into it. As the aromatic vapors rush through the coil, the water acts as a cooling agent and the essential oil begins to separate from the cooled steam. At the bottom of this second container is another tube connected to a vessel called an alembic, in which the essential oil and the water collect. Usually essential oils have a density lighter than water so they will float on top of the water.
After this the essential oil is separated from the water. The by-product of distillation is called a floral water, examples are rose water, orange water and lavender water.
The essential oils of citrus fruits such as Orange, Lemon, Mandarin, Bergamot, and Lime are extracted from their fruits using a method called expression. This is a simple method in which machines using a centrifugal force, squeeze the rind which produces the essential oil.
Enfleurage involves using a fixed oil, usually a vegetable oil, animal fat, or lard. A sheet of glass mounted on a wooden frame, is spread with the fixed oil. The raw materials, flower petals, are then placed on this. A number of these can be stacked on top of each other. These are then placed in the sun until the fixed oil is saturated with the essential oil.
This is then dissolved in alcohol then the alcohol is evaporated from the essential oil. This method is mainly used for delicate flowers such as Rose, Jasmine, Neroli, and Violet. These will be labeled 'absolute' rather than 'essential oil'. Enfleurage is quite rare as it is very expensive.
Very similar to enfleurage, maceration differs only in that the fixed oil is heated up to facilitate the release of the essential oil.
Solvent extraction is another method used to extract essential oils from delicate flowers such as Rose, Jasmine, Violet, and Mimosa. This method uses volatile solvents such as petroleum ether. The flower petals are placed on perforated metal trays. These are then sprayed with the solvent which is absorbed by the flowers to make them release their essences. Alcohol is then added to extract the essence. These are also called 'absolutes' but are a slightly less expensive essential oil extraction method than enfleurage.