Extraction is the process used to remove oil molecules from plant material. It’s important to understand extraction because it determines an essential oil’s properties, its benefits, how it’s purchased and ways it’s used. The four primary methods of extracting essential oils are steam or water distillation, solvent extraction and expression.
• Distillation by steam under pressure is the most efficient means of extraction. Plant material is heated, a vapor forms and when it cools the resulting liquid is essential oil. In water distillation, plant material is covered in water and heated in a sealed container; this method takes longer than steam pressure and risks damaging delicate components of essential oils from longer exposure to heat. Steam distillation is the preferred and most commonly used method of extraction.
• Solvent extraction is used for delicate petals such as jasmine and rose with a low yield of essential oil. This extraction is the end process of a method called enfleurage, where petals are placed on glass and covered with an odorless fat or oil. An alternate method is to stir flowers into heated oil. Flowers are added until the oil or fat becomes saturated with flower essence, forming a substance called ‘concrete’ or ‘pomade.’ The pomade is soaked in alcohol which absorbs the fragrance of the fat, and the two are separated. The alcohol is allowed to evaporate, leaving particulate plant matter, the ‘absolute’ essence of the flower. The fat is used in soap manufacturing. When a synthetic petrochemical such as hexane or benzene is used as the solvent, the aromatherapy benefits of the absolute are inferior to those obtained with alcohol solvent, an organic substance derived from sugar or starch.
• Expression is the method for extracting oil from the rind of citrus fruit such as bergamot, lemon and orange. Traditionally, this was a time consuming project done by hand; today, expression of rinds is mechanized. You may experiment with hand expression by cutting off a segment of peel from a washed and dried piece of fruit. Pierce the peel with your fingernail, or knife tip, and over a bowl use your fingers to squeeze drops of essential oil from the rind. Store this oil in a dark glass bottle in a cool place. This is as good as any commercially obtained essential oil of citrus and can be used in any form of aromatherapy.
• A fifth recently discovered method of extraction utilizes carbon dioxide (CO2) process at low temperatures. This method produces highly fragrant aromas and many aromatherapists believe the process is preferable to solvent extraction. The CO2 process, however, requires expensive equipment making these oils costlier, as well as rare and difficult to obtain. Opponents of this type of this process believe the temperature in CO2 extraction is not high enough to properly distill plant molecules and that essential oils processed this way should be reserved for non-therapeutic uses, such as soap, candles and room deodorizers.
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