Distillation of essential oil is both art and science. The most commonly used method is steam distillation. In this method, steam is injected into the still at a high pressure. The steam is then separated out to produce essential oil.
It is used for temperature sensitive materials like natural aromatic compounds. This is because some organic compounds tend to decompose at higher temperature and normal distillation does not suit their purpose.
Steam distillation is a physical distillation process and no chemicals are used, which ensures the purity of the essential oil hence produced.
Principle of Steam Distillation
When an amalgamation of two literally unmixable liquids is heated and at the same time agitated to expose the surface of each liquid to vapor phase, each constituent individually applies its own vapor pressure, as a function of temperature in a manner like the other component is invisible.
As a result of this process, the vapor pressure of the entire system increases and the boiling process is initiated as soon as the vapor pressure of those two liquids surpasses the atmospheric pressure.
This principle is used to extract essential oil from plant parts and since, the reaction is physical, no harm is done to the properties and you get 100% pure natural oil.
Process of Steam Distillation
When a high-pressured steam is passed through the plant material, it vaporizes the temperature sensitive compounds and separates the essential oil, which is quite insoluble in boiling water. The distillate that is acquired from the process contains a mixture of vapors and essential oil that go straight to condensing apparatus. The liquid form of essential oil is hence obtained and separated in a Florentine separator.
Steam distillation has many merits and therefore used widely, but fore mostly, It can retain delicate aromas that might not be acquirable in other distillation processes.