The chemotype of an EO is defined by the level of the molecule most present in the EO
For example, thymol thyme EO contains 50% thymol, which defines its chemotype. A molecule is generally taken into account within an EO only if it exceeds 10%. All EOs for which the percentage of molecules is not mentioned are only present in trace amounts.
The chemotype used in aromatherapy makes it possible to identify within the same species chemical variations of secondary metabolites which are due to environmental factors (altitude, sunshine, temperature, humidity, etc.). Thus the essence produced by two plants of the same species, despite their very similar genotype and morphology, may exhibit large variations in chemical composition. It is therefore a very important concept in aromatherapy.
We can extract an essence from any organ as soon as it has the structures to produce it. Thus many EO come from flowers, leaves, seeds, fruits, rhizomes, etc. The same plant from the same biotope (living environment characterized by a certain number of characteristics such as temperature, humidity, etc.) can synthesize essences with very different compositions and odors depending on the producing organ. considered. The best known example is that of the bitter orange tree from which we can extract 3 distinct EO. The leaves will give the EO of petit grain bigarade , the flowers will give the EO of neroli , while the peel of the fruit gives the essence of bitter orange peel.
The plant that will give the vegetable raw material can be cultivated or harvested in the wild. The conditions of cultivation, harvesting, drying, storage, etc. determine the quality of the plant and therefore that of the essence produced. If the plant is obtained by cultivation, it must at least be ecological and therefore do without chemicals (pesticides, weedkillers, etc.) likely to pollute the soil. The plant will also have to grow in its natural biotope or a very neighboring biotope.
There are different methods of extracting the essence produced by aromatic plants. Among these methods, the European pharmacopoeia retains only three to obtain a product which could be called essential oil: training with water vapor , dry distillation for the stems and bark in an appropriate device, or by a adapted mechanical process without heating for citrus trees.
Other techniques : There are other methods of extracting essences, however the product obtained cannot be defined as an essential oil.
Unlike vegetable oils, EOs are volatile, which allows them to be extracted with water vapor. With rare exceptions (cinnamon bark, cloves), their density is lower than that of water. They are immiscible in an aqueous medium but soluble in the usual organic solvents. HE are also active on polarized light and this property is used to control their quality. The rotatory power of an EO also makes it possible to highlight a pure and natural oil. Finally, their refractive index “ n ” is high. Of more or less pronounced colors, the whole spectrum is represented: from the blood red of certain savory, to the blue of Chamomilla recutita, passing through the pale green of Citrus bergamia. We can even observe the ultraviolet of mandarin under UV lamp.
EOs are complex substances, they can contain :
However, the composition may vary greatly depending on the plant producing the essence, its geographical origin, the climate, the altitude, the method of extraction, the know-how of the operator, etc.