5. Microwave hydrodistillation without organic solvents

5.1 Steam extraction

Steam distillation is the extraction method used to obtain an essential oil from a plant (with the exception of citrus fruits, for which a mechanical expression process can be used). In most cases, steam is injected at the bottom of a plant feedstock. The water vapour loaded with volatile molecules collected at the top of the charge is then condensed. By decantation, a hydrophobic fraction separates from the aqueous phase: this is the essential oil.

In this process, heat is transferred by condensation of part of the water vapour on the plant feedstock, with the liquid water condensed on the feedstock releasing the latent heat required to evaporate the essential oil.

In the case of "superficial" essential oils contained...