Essential Oils: Methods of Procurement
Historically, the importance of essential oils for medicinal and ritual purposes, as well as for medicine, is immeasurable. Let's take Ancient Egypt for example. To extract oils from plants, the Egyptians would squeeze the plant material in fine linen held on a frame at one end and twisted at the other end by a group of people. Various plant materials were also steeped in oils and fats of different kinds which when solid were formed into balls or cones and often used as hair decorations. In the heat of the sun, these would slowly melt and would then drip down the braided hair, conditioning the hair and perfuming the air.
Nowadays, most essential oils are extracted by steam distillations, employing heat and pressure to release drops of oil from the plant with the goal of isolating the essential oil molecules from the plant material. Distillation of the oils is an art and requires judging the correct combination of heat and pressure of the steam and the length of time the plant material undergoes the treatment. Each type of plant requires different conditions of extraction. Well-known byproducts of the distillation process include orange blossom, rose, and lavender.The water from which the oil has been separated in the distillation process becomes soaked with the fragrance of the oil and is sold under the name of "hydrolats" or "hydrosol" deriving from the French hydro for "water."
Another method of extracting essential oils is called "enfleurage". This is a labor-intensive, time-consuming process involving immersing the flower petals in fat so that the fat pulls the essential oil from the petal and becomes saturated with it. The fat and essential oil are then separated. The fats generally used today are vegetable fats such as cocoa butter or coconut. Enfleurage is still used in some places for extracting the essential oil from delicate flower petals and is typically very costly. Maceration is a variation of enfleurage involving the use of a liquid fat or oil heated to a temperature of over 60 degrees F. The material of origin may be flowers, leaves, and/or twigs.
Another method, known as "expression", is used to extract essential oils from the oil sacs present in fruit rinds. Orange, lemon, bergamot, mandarin, and tangerine are examples. In the past, this method was extremely time-consuming but today it is done by machines.
"Solvent extraction" is often employed for gums and resins, among other plant materials. Since this method involves the use of petrochemicals through which the essential oils are filtered, reputable aromatherapy companies often avoid essential oils and absolutes produced with petrochemicals.