Essential oils are used in lotions, creams, aromatherapy and perfumes and for many other purposes where pleasant aromas are needed. There are a number of methods used in order to extract the essential oils from flowers and other plant material. Essential oil makes up only a very small fraction of the plant or flower so a considerable amount of plant material is needed to make a small quantity of oil. More than a hundred pounds may be needed to make an ounce of oil. A number of flowers are also too delicate to use any of the cheaper methods and expensive and time consuming techniques must used. Essential oils are often very expensive however they are concentrated. Most recipes merely use a few drops so a tiny bottle will more than likely last for a long time.
Extraction by Steam Distillation
This method is the usual method for most of the essential oil manufacture. Steam under pressure is passed through flowers or other plant material spread on mesh screens in a still. The steam absorbs the oils which then enters a different chamber and cooled. On condensing the essential oil floats on the top of the water where it is skimmed off. The remaining water is referred to as floral water and is not wasted since it contains tiny quantities of the oil. It is used for toners and mists. Floral water can be used by those who are sensitive to essential oils since it is much less concentrated.
Solvent Extraction
For flowers or plants too delicate to use steam extraction, another method such as solvent extraction must be used. A solvent, usually hexane, is passed through the flowers on mesh trays, repeatedly. The esential oils, along with other soluble substances, are absorbed by the solvent which is filtered and then distilled under low pressure to take away the solvent. The material left, called a concrete, is a waxy solid containing the essential oils and waxes and pigments from the plant material. Some further processes are undertaken to extract the oils and waxes from the concrete. The concrete is used as a perfume and the waxes can be used in creams, lotions and for candle making.
Enfleurage
For those flowers and plants that have only very low percentages of essential oils, jasmine for instance, a different system must be used. Vegetable oil is used to soak the flowers and left for a few days and then replaced by fresh flowers. This process is repeated until the oil is thoroughly saturated with the oil from the flowers. The essential oils are extracted with alcohol from the vegetable oil. On evaporation of the alcohol the uncontaminated essential oil is left. This procedure is time consuming and uses a large number of flowers which makes the essential oil very expensive.
Cold Pressing
Some oils such as citrus, in which the oil is extracted from the fruit rather than the flowers, use a method called cold pressing. In this method the fruit is rolled through spikes which puncture the skin and then squeeze the fruit to extract the juices which contain the oil. The resulting juice is then centrifuged to separate and collect the essential oil.
Extraction using Carbon Dioxide
In this system carbon dioxide is employed to extract the oil. A high pressure is achieved by pumping the gas into a chamber that contains the plant material or flowers. As the pressure is increased the carbon dioxide liquifies and acts as a solvent. The gas is then allowed into into another chamber and the pressure released. The carbon dioxide vapourises leaving the essential oils behind.
As no residues are left behind the extract is very pure and has a lovely, fresh fragrance. As a much lower temperature is used than for steam distillation, oil can be extracted from delicate flowers that would be ruined by steam distillation.
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