Producing Essential Oils
The traditional technologies used in processing essential oil remain even today as a significant craft. Most commonly, these include Distillation, (water, steam or both) Maceration, CO2, Cold Pressing, Enfleurage, and Solvent techniques.
Originally introduced by Von Rechenberg, the distillation terms have become established in the essential oil industry. All three methods are subject to the same theoretical considerations which deal with distillation of two-phase systems. The differences lie mainly in the methods of handling the material.
Some volatile oils like citrus cannot be distilled without decomposition and are usually obtained mechanical means – pressing. The general method for obtaining citrus oil involves puncturing the oil glands by rolling the fruit over a trough lined with sharp projections that are long enough to penetrate the epidermis and pierce the oil glands located within outer portion of the peel (ecuelle method). A pressing action on the fruit removes the oil from the glands. A fine spray of water washes the oil from the mashed peel while the juice and pulp is extracted resulting in a oil-water emulsion is separated by centrifugation. A variation of this process is to remove the peel from the fruit before the oil is extracted.
Often, the volatile oil content of fresh plant parts (flower petals) is so small that the removal of oil is not feasible using either distillation of cold press methods. In such cases, an odourless, bland, fixed oil or fat is spread in a thin layer on glass plates. The flower petals are then placed on the fat for a few hours; changing the oil petals repeatedly until the fat layer has absorbed as much fragrance as possible. The oils itself is then conmonly removed by extraction with alcohol. This process, is known as enfleurage, a process that was once extensively in the production of perfumes.
In the perfume industry, modern essential oil production is now accomplished by extraction, using solvents such as petroleum, ether and hexane. This enables a uniform temperature (usually at 50° C) to be maintained during the extraction process, As a result, extracted oils have a more natural aroma that is unmatched by distilled oils. Distilled oils sometimes undergo chemical alteration under the high temperature. Nonetheless the distillation method is a lower cost than the extraction process and not preclusive through aromatic changes in oils outside the perfume industry.
For more details about essential oil production including home-based extraction read our posts below.
