Essential Oil Distillation
Steam distillation is without a doubt the most frequently used method for extraction of these precious oils from plants. “To extract the essential oil, by steam distillation the plant material is placed into a still (very similar to a pressure cooker) where pressurized steam passes through the plant material. The heat from the steam causes globules of oil in the plant to burst free from the cells walls due to the increasing pressure and the oil then evaporates. The essential oil vapor and the steam then pass out the top of the still into a water cooled pipe where the vapors are condensed back to liquids. At this point, the essential oil separates from the water and floats to the top.”7 The advantages and disadvantages of steam distillation are as follows:
- The amount of steam and the quality of the steam can be controlled.
- Lower risk of thermal degradation as temperature generally not above 100 °C.
- Most widely used process for the extraction of essential oils on a large scale.
- Throughout the flavor and fragrance supply industry it is the standard method of extraction.
- There is a much higher capital requirement and with low-priced oils the pay back period can be over 10 years.
- Requires higher level of technical skill and fabrication and repairs and maintenance require a higher level of skill.”9
The type and variety of Steam Distillation plants vary greatly all over the world. This ranges from the use of traditional and sometimes primitive methods in developing countries to the use in industrialized countries of technologically more evolved and complex computer aided equipment. While these methods are vastly different both can produce excellent oil. The true difference comes from the operator’s skill and experience. Generally, the process of steam distillation is the most widely accepted method for the production of essential oils on a large scale.”
Dry Distillation, has been permitted under ISO Standard 9235, which states that products of dry distillation without added water or stream are in fact essential oils. This method involves the heating without aerial oxygen in a closed vessel thus preventing combustion. The plant material used in this process is broken down into new chemical substances. Birch Tar and Cade oil are made this way but as both oils contain carcinogenic phenols they are no longer commercially demanded. Today dry distillation is only used in very rare cases.