1. Definition

According to Naves, none of these definitions of essential oils is clear or precise. This author defines essential oils as mixtures of various products from a plant species, these mixtures passing with a certain proportion of water during distillation in a stream of steam [238] .

This definition can be extended to essential oils obtained by cold expression of the rind or zest of Citrus fruits, because of the intervention of water in the mechanical processes to entrain the product released from the oleiferous alveoli.