Essential Oils - A Guide To Their Production

Essential oils are used in lotions, creams, aromatherapy and perfumes and in other products where pleasant aromas are needed. A variety of methods are used to extract essential oils from plant material and flowers. Essential oil makes up only a tiny percentage of the plant or flower therefore a considerable amount of plant material is needed to make a small quantity of oil. More than a hundred pounds might be needed to make one ounce of oil. A number of plants are also much too delicate to use any of the easier techniques and labor intensive and time consuming ways must used. Essential oils can be expensive but they are very concentrated. Most recipes merely use a very small amount so a small bottle will last for a many months or years.

Extraction by Steam Distillation

This technique is used for nearly all the essential oil manufacture. Steam that is under pressure is passed through flowers or other plant material that have been placed on mesh screens in a still. The oils enter the steam which then is lead to another chamber where it is cooled down. After condensing the essential oil floats to the top of the water and is skimmed off. The remaining water is known as floral water and has many uses since it contains small amounts of the essential oil. It is used for facial mists and toners. Floral water may be used by people who are sensitive to essential oils because it is less intense.

Solvent Extraction

For plant material or flowers that are too delicate to use steam extraction, another method such as solvent extraction must be used. A solvent is repeatedly passed over the flowers on mesh trays. The oils, along with other substances that are soluble, dissolve in the solvent which is then filtered and the resulting solution distilled to take away the solvent. The resulting material is called concrete which is a waxy solid containing the waxes, pigments and the oils from the flowers. Some more processes are then used in order to extract the oils and waxes from this concrete. The concrete is used as a perfume and the waxes may be used in creams, lotions and for candle making.

Cold Pressing

Some oils such as citrus, in which the oil is extracted from fruit, use a technique known as cold pressing. This entails rolling the fruit through spiked projections which penetrate the peel and then squeeze the fruit to extract the juice containing oils. Centrifuging is then used to separate the essential oil.

Enfleurage

For flowers or plants that have only very low levels of essential oils, for example jasmine, a different method must be employed. Flowers are placed into odourless vegetable oil and left for a few days and then the plant material is replaced. Fresh flowers are repeatedly placed in the vegetable oil until the oil becomes thoroughly soaked with the oils from the plant material. The essential oils are extracted with alcohol from the vegetable oil. On evaporation of the alcohol the uncontaminated essential oil is left. This technique is time consuming and needs a large quantity of flowers resulting in very expensive essential oil.

Carbon Dioxide Extraction

In this method carbon dioxide is used to remove the essential oil. The gas is pumped into a compartment containing the plant material or flowers. When the pressure increases the carbon dioxide liquifies and absorbs the oils. The gas is then allowed into into a different compartment and the pressure released. The gas then vaporises which leaves behind the essential oil.

As no impurities are left the extract is very pure and has a lovely, fresh fragrance. Since a much lower temperature is used than for steam distillation, oil can be obtained from delicate flowers and plants that would be destroyed by steam distillation.