Essential oil 'volatile or aromatic oil' is a mixture, obtained from plant material, of volatile, aromatic constituents characteristic of the smell of the plant from which they are extracted. Although such mixtures are called 'oils', essential oils do not contain fat. They are liquid at room temperature, but evaporate quickly when heated and ignite easily.
They are extracted from different parts of a plant, for example the blossom, the fruit, the seed, the leaves, the skin, the bark or the wood (of stem, branches or roots). Usually a plant contains no more than 1% essential oil, but in the case of nutmeg and cloves that is more than 10% essential oil. Sometimes different parts of a plant contain different volatile oils.
Essential oil is mainly produced from members of the following plant families: umbelliferous family, composite family, cypress family, lipflower family, myrtle family and wine family.
Some types of volatile oil are quite expensive, because sometimes many plants are needed to produce a small amount of oil. A cheap oil is for example orange oil, because the peel of oranges are a waste product of the juice industry. For example, expensive is rose oil, because many roses specially cultivated for the oil are needed to produce volatile oil. Perfume oil is cheaper, but also less strong. Perfume oils are chemically composed and are intended to artificially imitate a fragrance.
The word ethereal comes from the Greek aither, which literally means air from heaven. With aither the Greeks indicated the lowest layer of the cosmos. Sometimes it is spelled "essential oils". The essential oils are volatile and strongly scented, just like ether.
Essential oil is sometimes called essential oil.
Volatile oil is extracted in different ways. Most volatile oil is extracted by means of steam distillation. Steam is led through the plant parts to be processed. The volatile oil evaporates with the steam. After the steam has cooled down to water, and the volatile oil has also become liquid again, the volatile oil can be separated from this by the difference in polarity between the oil and the water.
One method used in citrus fruit is the pressing. The oil-bearing skin of the plant is pressed out and the oil emerges.
Volatile oil is extracted from a few types of wood by dry distillation. In this process, the solid is carefully heated, whereby the volatile oil evaporates. This vapour is then condensed.
Other methods are:
Liquid extraction, but strictly speaking this does not result in volatile oil, but in an extract, whereby the parts to be extracted are boiled in water and the oil from the evaporating vapour is collected. This is common with clove oil, for example.
enfleurage, this actually results in a pomade instead of a volatile oil. This method is not or hardly used anymore because of the high costs.