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Essential Oil Extraction through Steam Distillation
Essential oils are aromatic oils originating from various parts of the plant, such as the flowers, roots, leaves and stems. They have been known not only for their aromatic contribution to various cosmetic products, but also for their medicinal properties.
How do I extract these oils?
There are numerous methods used for the extraction of essential oils such as Hydro distillation methods, Solvent extraction, Expression, Maceration, and Supercritical CO2 extraction. However, hydro distillation and expression are two of the most widely used methods.
To find out more about the differences between hydro distillation methods and expression, read our article on Essential oil extraction through distillation.
How steam extraction (Hydro distillation) works:
To isolate the essential oils by steam extraction (hydro distillation), the plant material is placed in a column above the boiler that is filled with water. The water is then brought to a boil and due to the high temperature of the steam, the essential oils are released from the oil glands (or Glandular Trichomes) in the plant tissue and carried with the vapour to the condenser. The vapour mixture of water and oil is condensed by the cooling water and collected in an essential oil separator where the oil and hydrosol (water mixed with water-soluble compounds from the plant material) are allowed to naturally separate.
Figure 1: Premium Alembic Essential oil still
Figure 2: Separation Funnel
Can all essential oils be extracted via steam distillation?
Not all essential oils can be extracted via hydro distillation. This is mainly due to the heat sensitivity of some essential oils in the plant material – especially delicate flowers. Different plant species will require specific extraction methods depending on their unique characteristics. Research should be done on the best extraction method for each plant-type.
Hydro distillation extraction methods can be used for these typical garden plants:
- Citrus such as lemons, lime, oranges
- Dry your plant material for 24 – 48 hours after harvesting – this will allow for most of the water to evaporate, concentrating the essential oils.
- Cut your plant material in fine pieces – this increases the surface area of the plant material which allows for better extraction.
- Ideally you would want a shorter column with a wider diameter. The longer the column, the bigger the temperature difference between the base and the highest point of the column. As discussed earlier, the essential oils are carried with the vapours out of column. The bigger the temperature variation, the more reflux would occur, causing the essential oils to fall back into the boiler.
For a comprehensive understanding of essential oil extraction and the different extraction methods, have a look at our E1: Extraction methods and essential oils course.