This article covers the concepts underlying the practice of producing essential oils steam distillation.
What is Steam Distillation?
“Steam distillation is a popular technique that is used to recover volatile compounds with high boiling point, from inert and complex matrices, solid or liquid, using saturated or superheated steam as separation and energy agent.”
Steam Distillation Technique for Extraction of Essential Oils
Steam distillation is one of the most common methods for extraction of essential oils and fragrances from botanical resources.
In practice, the process uses water and/or steam as extracting agent to vaporize or liberate the volatile compounds from the raw material. The compounds are volatilized by absorbing heat from the steam, and are then transported to the steam where they are diffused.
The resulting vapor phase is cooled and condensed prior to separating the water from the organic phase based on their immiscibility.
As result of steam distillation of essential oils, we get 2 components which are:
- Volatile oil
The volatile oil floats above the hydrosol in the receiver. Hydrosols can also be referred as byproducts of the essential oil distillation process.
Types of Steam Distillation Method:
There are 3 types of the steam distillation process which are:
- Dry steam distillation
- Direct steam distillation
- Hydro/Water distillation
Direct steam distillation:
This method does not allow direct contact with water, whereas the boiler can be inside or outside the still. The low-pressure saturated steam flows up through the matrix, collecting the evaporated compounds.
Hydro Steam Distillation:
In this process the matrix remains in direct contact with the boiling water either by floating or by being completely immersed depending on its density. The boiler is inside the still and agitation may be necessary to prevent agglutination.
Dry Steam Distillation
In dry steam distillation technique, matrix is supported and steam passes through it. The differences are due to the steam being generated outside the still and superheated at moderate pressures.
Benefits of Steam Distillation Method Over other techniques for Extraction of Essential Oil:
Steam distillation is the most prevalent essential oil manufacturing technique as it has several advantages when compared to other extraction processes:
- Steam distillation is preferred as it produces organic solvent-free products,
- No need for subsequent separation steps,
- It has a large capacity for processing at the huge scale,
- The apparatus required may be inexpensive
- Sufficient studies and industry know-how build up confidence for distillers to use steam distillation.
Drawbacks/Challenges of Steam Distillation:
- Certain sensitive compounds may lose their value or medicinal properties
- Very long extraction times. May take from 1 to 6 hours depending on substances
- High energy consumption