2. Production techniques

There are three general methods for obtaining essential oils:

• steam distillation of fresh or dried plants and hydrodistillation with the addition of water to the plant or to a natural gum-resin;

• cold expression of the pericarp or zest of Citrus fruit;

• pyrogenation of the bark or wood of certain plants (birch bark, cade wood).

In the case of steam distillation and hydrodistillation, these methods have long been based on primitive or traditional industrial equipment (fixed or portable stills heated over an open fire, industrial plants with steam generators). Over the last quarter century, however, technological improvements have been made: overpressure distillation, turbodistillation, hydrodiffusion, continuous distillation and microwave-assisted...