Plants have accompanied man since the very genesis of our history. Over time, we have learnt to recognise them, cultivate them and use them, even deciphering them and determining their exact compositions. Now we know how to extract their very best, and it is in essential oils that we find the quintessence of the plant kingdom.
A look back on these powerful fragrance essences from aromatic plants …
Thanks to the long process of evolution and the resulting selection, plants have been able to adapt to defend themselves and withstand various environmental conditions. Some have transformed morphologically, while others have evolved their metabolism to develop molecules of interest, involved in various functions such as insect control, reproduction or even communication(1). It is from this last large group of aromatic plants that we today derive essential oils, concentrated extracts of these fragrant volatile metabolites.
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To recover this precious liquid, it must be carefully separated from the plant, with the art of extraction primarily based on the know-how and mastery of the process used(2), which, depending on the plant in question, may be:
Finally, it is sometimes necessary to resort to secondary processes (rectification/fractionation/redistillation) in order to select olfactory notes or to remove certain molecules according to their desired use.
The essential oils obtained in this way can be classified according to various typologies: though they may be associated with the botanical family of the plant from which they are derived or according to their chemical family, perfumers prefer a classification according to their olfactory properties.
It is for this reason that we find the charm and poetry of terminology used in the world of perfumes to describe these families. As a result, we speak of floral (ylang, geranium, rose), hesperidic (lemon, orange and bergamot), woody (vetiver, patchouli, cedar, pine), aniseed (fennel, tarragon, star anise, aniseed), spicy (clove, carrot, parsley) and aromatic (lavender, sage, rosemary) notes, among others.
Essential oils are complex natural mixtures, which may, unfortunately, be modified by the deliberate or accidental addition of substances of lesser value (synthetic or natural) or contaminants.(5).
However, the term "essential oil" may only refer to a pure and natural product: it is the criterion of quality par excellence. To meet these requirements, the regulations impose standards represented by an analytical triptych: organoleptics, physicochemistry and chromatography.
Each essential oil has typical organoleptic, physicochemical and chromatographic characteristics, guided by standards. They are defined by bodies such as AFNOR(6), ISO(7) or the European Pharmacopoeia(8). These characteristics are dependent on the variety of plant used, the means of production, seasonality and the geographical area of cultivation. In addition to the panel of typical molecules, details of oxidation, ageing and contamination are investigated(4) in order to confirm the quality of the essential oil.
To ensure the purity of the essential oil, we must increase our standards and the technicality of our analyses. Chiral chromatography is therefore used to verify the spatial configuration of molecules or to evaluate the amount of stable and unstable carbon and/or hydrogen isotopes. These techniques allow us to validate the product's naturalness, or even to assume its geographical origin.