Process for the expression of essential oils
Expression consists in mechanically breaking the "essence pockets" in the fresh zest of citrus fruits to extract the essences.
This method is the simplest but it is only possible with citrus fruits (orange, lemon, bergamot). The product obtained is called "essence" and not "essential oil".
Other extraction methods :
Other extraction methods exist, which we will detail below.
- Percolation or hydrodiffusion : this method consists in sending steam downwards. It is faster and gives a higher quality of aromatic substances, but charges the essential oils with non-volatile substances. We then speak of "percolation essence".
- Supercritical CO2 extraction : ultra-modern and highly expensive, this method consists in passing a current of CO2 at high pressure which bursts the essence pockets and brings out the aromatic substances.
- Enfleurage : enfleurage is normally reserved for flowers containing very low concentrations of essences (jasmine, mimosa etc.). The flowers are put into contact with absorbent fats that gradually become saturated with essence. The ointments thereby obtained are used as they are or exhausted by absolute alcohol. We thereby obtain alcoholic flower extracts referred to as "absolute".
- Exhaustion procedure : the extraction of the essences can take place using volatile solvents (benzene). We obtain concretes of flowers and leaves which become absolute by alcohol exhaustion and then "concrete essences" after evaporation. Concretes generally contain 2 to 3% residual solvents. These essences are therefore only suitable for olfactory therapy.