Quality of Extraction Methods for Essential Oils

The different methods of extracting essential oils

Distilled essential oils are the primary aromatics of choice for aromatherapy. Distilled oils, however, vary greatly in quality. Oils are adulterated in numerous ways undetectable to the untrained nose. "Doctoring the sauce" is a common practice of commercial manufacturers. Essential oils are extended with vegetable oil, mineral oil, or alcohol. Synthetic constituents are added to make the oil more marketable. For instance, to extend costly rose oil, a constituent such as synthetic geraniol will be added. These mixtures of synthetic aromas and natural essential oils are often sold as pure essential oils. Besides synthetics, natural essential oils are also blended with other essential oils (e.g., yarrow may be added to chamomile, lemongrass to lemon). The more costly the oil, the more common the practice of adulteration.

Another common practice is to rectify essential oils by re-distillation, thereby increasing a desired constituent and removing undesired components such as terpenes. However, rectified or deterpenated oils are not suitable for aromatherapy purposes, which require complete oils. Complete oils buffer users from chemical compounds contained in the oil, which in their isolated state might cause harmful and allergic reactions. This kind of adulteration accounts for many of the cases of allergic reactions to oils.

Specialized distillation methods are used for essential oils intended for therapeutic use. One such method is water steam distillation, keeping the temperature lower than the lowest boiling point of the essential oil within the plant material being distilled. This low temperature preserves the integrity of the essential oil and some of the more volatile compounds in the oil sacs of the plant material.
Cold-pressing, an excellent method for extracting oils, is used only for the Rutaceae (citrus) family of oils. Citrus oils such as bergamot are technically not essential oils but essences, because they contain natural pigments. Citrus oils prepared for commercial use are deterpenated, making them inappropriate for aromatherapy.

Each species of plant must be distilled for a different length of time in order to extract all the chemical components. This is very important in aromatherapy, because it is the synergy of the plant's essence that does the job: The main constituents are no less important than the minuscule constituents. This synergy enables essential oils to work on many levels simultaneously. Incomplete oils do not have this depth of physiological action. In Rosa damascene (rose oil), for instance, minuscule constituents that account for less than 1 percent of the total are essential in composing the fragrance and creating the medicinal action of the oil.

Length of distillation time greatly affects the quality of oil yielded. The different grades of ylang (Cananga odorata) are an example. Ylang-ylang extra, the finest grade, is distilled for as little as twenty minutes. Ylang-ylang one, also good quality, is distilled for two hours. The lesser grades two and three are distilled up to twenty-four hours and have a chemical profile totally different from that of the first two grades.