Steam distillation of essential oils – Episode n°2: Precious raw materials, each with its own specific processing characteristics

Rose, iris, bergamot, vetiver, ylang ylang, agarwood…: each natural material is unique. And, each one has its own particularities when it comes to obtaining its precious essences.

When talking about essential oils, it is the steam distillation process that comes to mind. This process, which consists of using steam as a vehicle to draw out the volatile essences contained in natural materials, has many variations depending on the type of material to be processed. Sometimes, the essential oil does not need steam, as is the case for many citrus fruits, including bergamot. The essence of the citrus bergamia fruit is obtained by cold expression of the fruit peels. These contain vesicles rich in essential oil, released by simple mechanical action.

As for the emblematic Damask rose, its elegant perfume is the image of its delicate flower: it needs to be bathed in a boiling water bath to release its essences to the water vapors created during the process. Iris, on the other hand, requires a more energetic treatment: its rhizome, from which the highly appreciated iris butter is extracted, is generally crushed directly in the still during the distillation process, which is also carried out in a water bath. A small nuance here: the aromatic butter, obtained after condensation of the vapors and separation in the Florentine flask, solidifies at room temperature. It therefore requires a well-controlled “hot flow” in order to avoid abandoning part of it in the piping.

Other plants, such as ylang ylang, also have specific processing requirements. We collect different fractions of essential oil depending on the pressure at which the still will operate. During the distillation process, a pressure gradient is applied in increments (from atmospheric pressure to 1.5 bar) in order to successively extract the essential oil of ylang extra, then the essential oil of ylang 1st, then 2nd and so on – each with its own distinct aromatic profile.

With 190 years of experience in the design of steam distillation units, Nature & Technologies offers the most complete range of stills for the production of essential oils from all kinds of plants: leaves, flowers, twigs, roots, seeds, chips, bark, powders, rhizomes, etc.