Essential oils a volatile oils extracted from plants by distillation with either water or steam or by mechanical process of citrus rinds. The “essence” is the oily, fragrant substance contained within pockets of cells of plant. When the essence is extracted using distillation or by mechanical process of citrus rinds it is called an ‘essential oil’.
Essences may be produced in the leaf, bark or other parts of the plant. They may be stored within the leaf and the essence is released if the leaf is crushed. They may be stored on the surface of the leaf in minute hairs, and will release their perfume when simply brushed against the tiny hairs and let the essence into the air.
In some woody plants and trees, the essence is stored in ducts in the fibrous parts of the wood or bark. In citrus fruits the essence is found in relatively large storage sacs in the peel and is very easy to extract by means of pressure.
Essences may have been developed by the plants to keep grazing animals away, or to attract pollinating insects, or may act internally as individual pesticides or fungicides. Essential oils are actually ‘compounds’ due to their chemical analysis and from chromatography (the collective term for a set of laboratory techniques for the separation of mixtures).
Each essential oil consists of many organic constituents that unite in a delicate, complex balance to produce a wide range of therapeutic and olfactory qualities. For example, Eucalyptus contains about 250 different constituents. Australian Tea Tree essential oil has been identified by researchers to have about 40 constituents.