Methods of Extraction
The essential oils we use are regularly extracted from many different plants and fruits. There are several methods of producing these natural aromatic ingredients, some more applicable than others, depending on the physical and constituent properties of the originating source. Our essential oils are extracted by the processes of Distillation and Expression.
Distillation can be described as a process by which volatile matter (from flowers, leaves, stems, twigs, leaves, herbs, spices, wood and roots) is converted into a vapor, which is subsequently cooled, allowing a condensed liquid to be collected.
There are a few different types of distillation significant in the production of essential oils, and the choice of method is often dependent on the following factors;
a) Sensitivity of the essential oil to the action of heat & water
b) Volatility of the essential oil
c) Water solubility of the essential oil
The different distillation methods are Water, Steam, Fractional water and/or steam, and Dry (non-destructive).
The process of steam distillation is known to be faster than water distillation, as steam (from a boiler) is blown into the distillation vessel, instead of boiling water. The condensed mixture of water and essential oil is then separated.
For example, Lime oil is produced by steam distillation; the process involves a pre-stage of producing the juice with a screw press allowing the oil glands in the peel to burst releasing lime juice.
The pressed juice is subsequently pumped into a stainless steel still, and is subjected to the steam distillation process for approximately 10 hours. The average yield of distilled oil is 4kgs, per metric tonne of limes (0.4%).
A few essential oils such as those present in citrus fruit peel (e.g. Bergamot, Orange and Grapefruit) are obtained by pressing (Expression) which yields a product of superior quality.
The process of Machine Abrasion (Expression) is applied to citrus oils, and is used to release the essential oil contained in the oil cavities of the outer cells of the colored rind.
Within this process the oranges are fed from a hopper into a rotating drum, consisting of rows of spikes. The stripped peel contains a mixture of cell debris, essential oil and other cell contents; these are washed away (with water) into a centrifugal separator. The essential oil is collected in a separate vessel for bottling.