WHAT ARE ESSENTIAL OILS?
Essential oils are a concentrated hydrophobic liquid containing volatile chemical compounds from plant material including grasses, leaves, flowers, needles, twigs, peels of fruit, seeds, bark, and roots.
For example, rose essential oil comes from the flowers, basil oil from the leaves, lime from the rind, anise from the seeds, sandalwood from the wood, frankincense essential oil from the resin of its tree, and so on.
What Methods are Used for Extraction of Essential Oils?
There are two prevalent methods that are used widely for extraction of essential oils, first is distillation and other one is expression method. Besides, there are absolutes (a form of essential oils) which are generally extracted using Solvent Extraction.
Method 1: Distillation Method for Essential Oil Extraction
Distillation of essential oil is ancient practice which has been there for centuries. Hundreds of years ago people used distillation method for extraction of essential oils. Today, the same method is followed for extraction of essential oils. However, with technological advancement, old traditional set up has been replaced by new and advanced machinery.
Distillation is the most common and widely used process for extraction of essential oils.
How Does the Distillation Process work?
In distillation process plant materials are placed in a large container known as “still” and pressurized steam is injected through an inlet through the plant material.
When the temperature increases due to steam, the vaporized plant compounds travel to the condensation flask or the Condenser. There are 2 separate pipes in place allow hot water to come out and for cold water to enter the Condenser. This makes the vapor cool back into liquid form.
It is important to understand that steam needs to be hot enough to allow the release of the essential oil at the same time it must not damage the plant material.
The liquid by-product drops from the condenser and collects inside a receptacle underneath it, which is generally referred as “Separator”.
Steam distillation of plant materials generally yields two products: a relatively high purity essential oil and an aqueous condensate called a hydrosol.
The essential oil, being lighter than the water, will float to the top and can then be separated from the water. The water by-product of distillation process is called hydrosols or floral water.
Types of Distillation Methods to Produce Essential Oil
The types of distillation include:
In water distillation, the plant material comes into direct contact with the water. This method is prevalent for distillation of flowers (rose and Champaca), as direct steam may cause these flowers to clump together which makes it difficult for steam to pass through.
Water and Steam
Water and Steam method of distillation is generally used with herb and leaf material. In water and steam distillation, the steam can be generated either in a satellite boiler or within the still, although separated from the plant material. During process, the water remains below the plant material, which has been placed on a grate while the steam is introduced from outside the main still (indirect steam).
Steam distillation is the most popular one to extract essential oils. In this process, steam is injected into the still on slightly higher pressures and temperatures than the other methods of distillation.
Percolation or Hydro-diffusion
Diffusion of essential oils and hot water through plant membranes is known as hydrodiffusion.
Percolation or Hydro-diffusion is a relatively new method of distillation and is very similar to steam distillation. The only difference is that the steam comes in through the top rather than the bottom, and there is a shorter distillation time. Essential oils that are extracted from wood or hard material are produced using this method of distillation.