Other methods of extraction

There are more methods of extraction. See below

Percolation or Hydrodiffusion

This method consists of sending high pressure water steam onto a plant material from top to bottom. It is more rapid, give a better quality aromatic material, but the major inconvenient is that some non volatile molecules are also carried out by simple gravity. Such aromatic extracts are called “Percolation essences”

Extraction with supercritical CO2

This is a recent and expensive method, consisting of sending a stream of high pressure CO2 in order to let burst the essence collecting organs and to carry out the aromatic volatile molecules.
This process would respect thoroughly the integrity of the original essence. There are almost no biochemical changes of aromatic molecules: this can be seen when a CO2 extract of german chamomile is obtained. This extract is almost colourless whereas an essential of german chamomile has a dark blue colour caused by the biochemical transformation of azulene into chamazulene.
CO2 extracts are rather waxy and uneasy to dissolve. They are only available for about 20 aromatic plants.

The enfleurage

The “Enfleurage” method is restricted to flowers containing very tiny concentrations of essences (jasmine, rosa centifolia, mimosa, ..). The flowers are put in contact with absorbing fats which become gradually saturated in essences. Afterwards rough aromatic extracts are isolated by centrifugation; they are use as such (the extract is called “concrete”) or are further purified by using absolute alcohol. The obtained alcoholic extract is called “absolute”.

Process of “Depletion”

Here the aromatic essences are extracted by chemical volatile solvents (benzene, hexane, toluene…). The obtained solutions are called “concretes of flowers and leaves” and become “absolutes” after their purification (literally “depletion” or “exhaustion”) with absolute alcohol.
This type of essence generally contains 2 to 3% residual solvents and may not be used for therapeutic purposes because of this chemical “pollution” of toxic solvents.