Production of Essential Oils

Producing Essential Oils

High quantities essential of oil products include turpentine, orange, lemon, mint and citronella. Oils were extracted by pressing before the process of distillation was discovered. However, there are still cultures in the world, such as in Egypt, that still use the pressing methods.

During traditional Egyptian practices the pressing process, consists of pressing the plant material, then burying it in ceramic containers in the desert for months in order to drive out the water. Water will disperse through the ceramic vessels, but the larger essential oils will not. Lotus oil was pressed in that manner. That oil was contained in King Tut's
tomb and it retained its scent after being sealed for 3,000 years in alabaster vessels.

Today the most common essential oils are distilled. These oils include lavender, peppermint and eucalyptus. Raw plant materials such as flowers, leaves, wood, bark, roots, seeds or peel are put into a distillation device called an alembic, over water and the unstable (volatile) compounds become vaporized when the water is heated. In this process, the vapor flows into a cooling tank, then when the steam condenses, the essential oil floats to the top. (The oil is able to do so since it is lighter than water.) This water is considered a hydrosol, hydrolat or plant water essence. Rose water, lavender water and orange blossom water are common hydrosols. Oils are usually distilled in one single process, although ylang-ylang takes about 22 hours to complete and is fractionally distilled, which means it produces several grades.

Citrus peel oils are expressed by mechanical means or can be cold-pressed. Such oils are normally by-products of the citrus industry and are, therefore, less expensive than most distilled oils.

Most flowers contain very little volatile oil so they are too fragile to be distilled. In the alternative, a solvent, which may be hexane or supercritical carbon dioxide, may be used to extract a mixture of essential oil and other oil solubles (lipophilic plant material). The solvent can then be removed by the distillation process and used again. Another solvent, usually ethyl alcohol, may then be used for extraction. A second distillation process takes place in order to remove the alcohol and an absolute is left. Absolutes are the kinds of essential oils that are extracted from plants such as jasmine and rose.

When supercritical fluid extraction is needed, a high pressure carbon dioxide gas, up to 100 atm, is used as the solvent. Petrochemical residues in the extracted product can then be avoided. This technique is identical to that used in making decaffeinated coffee.

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Essential Oils Information