A bit of pleasure and a bit of bureaucracy. Essential oils have their own rules of quality and everyone who deals with them should know the basic ones.
Essential oils have a special status among plant extracts, most likely due to their fragrant properties, price and the fact that they have always been “royal” plant extracts – only a small amount of essential oil is extracted from very large amount of plant material. Sometimes “only” a hundred kilograms of plant material is enough to get a kilogram of essential oil, and sometimes it is tons. An average of over four tons of rose petals are needed for a kilogram of rose essential oil.
Most essential oils are liquid at room temperature, but there are exceptions. Rose essential oil at temperatures below 20°C becomes a solid due to naturally occurring plant paraffins, and elecampane essential oil (Inula helenium) is a solid and melts only at elevated temperatures. Most essential oils are not very viscous, in any case less viscous than vegetable oils and even water. But some are very viscous, like the essential oils of vetiver and patchouli. Likewise, most essential oils are less dense than water (relative density is less than 1) and therefore float on the surface of water. Only some essential oils like German chamomile and clove are denser than water.
The volatility of essential oils is their fundamental characteristic, that is, the molecules of the essential oil evaporate easily. This allows us to detect them by the sense of smell. But volatility does not mean that essential oils boil at temperatures below 100°C. Most molecules of essential oils boil at temperatures above 150°C.
All essential oils are lipophilic molecules, which means they like “fatty” solvents, not polar solvents like water. Therefore, they are not soluble in water, but dissolve well in vegetable oils and waxes, concentrated ethanol (90 and more percent ethanol), diethyl ether and similar solvents. The molecules of essential oils are mostly low molecular weight and are made up mostly of carbon molecules with 10-15 carbon atoms. High lipophilicity and low molecular weight give them biological characteristics, so they are very easily absorbed through the skin, but also in general through cell membranes, which includes easy absorption in the digestive system and rectum. Their volatility allows for easy inhalation, so for centuries they were the only drugs that could be used that way.
Only extracts obtained by the following methods may be referred to as essential oils:
- steam distillation (most essential oils)
- pressing (citrus peel oil)
- direct heating of plant material without steam distillation (extremely rare, sometimes for cinnamon bark oil)
All other fragrant extracts obtained in a different way are named according to the method of preparation, for example n-hexane and CO2 extracts, and should not be called essential oils. Synthetic mixtures or mixtures of synthetic fragrances with natural essential oils should not be called essential oils, but only fragrances (INCI: fragrance).
All essential oils must be botanically and chemically defined. Botanically defined means that the species, possibly the subspecies, variety and form must be accurately identified, as botanical characteristics are of great importance for the chemical composition of the oil. Chemically defined oil has a precisely defined proportion of individual molecules in the essential oil, usually expressed as a percentage (%), and determined by chemical analysis of gas chromatography. If necessary, the chemical analysis accurately defines the chemotype, the phenomenon when botanically same material can give, depending on the place of growth, essential oils of different composition, as is the case with thyme, rosemary, niauli and many other essential oils.
In addition to these definitions, the essential oil must be properly labelled. Mr.sc. Jasminka Papić from the Croatian Institute of Public Health gave an excellent overview of how essential oil must be labelled according to international guidelines.
First, it is necessary to correctly label the classification as hazardous substances. According to the old regulations (DSD Dangerous Substances Directive 64/548/EEC) and (DPD Dangerous Preparations Directive 1999/45 / EEC), the following labels were used:
Many are unpleasantly surprised when they see the label “irritating” or “harmful” on a bottle of essential oil for massage because they are immediately afraid that the oil will have a negative effect on health. Imagine now that someone is transporting 200 litres of thyme essential oil chemotype thymol. Those 200 litres can really be harmful and irritating if an accident happens.
Furthermore, a well-labeled essential oil should contain the following labels:
- name… Lavender essential oil
- Latin name of the plant from which it was produced… Lavandula angustifolia Miller
- the part of the plant from which the oil was produced…flower
- main components (chemotype)… linalyl acetate, linalool, β-ocimen
- method of production… steam distillation
- cultivation method… traditional cultivation, organic cultivation
- country of origin… France
- allergens among the components… geraniol, limonene, linalool
- toxicological label… or
- other warnings (keep out of reach of children, phototoxic, etc.)
- shelf life… best used by…
- batch identification (batch or lot)
- other standard indications required when labelling items of general use and food
Of course, it would be impossible to always list everything on a small bottle, but most responsible manufacturers accurately state items 1-8, and items 9, 11 and 12. Other items are mostly listed on the corresponding certificates.