The facts about essential oils Part 3 of 5
Expression is the physical process of squeezing the oil out of the plant material. For essential oils it is only used for the Citrus Oils where the oil is held in small sacs on the surface of the outer peel. Other oils produced by expression such as nut and vegetable oils are known as fixed oils as they are not volatile. These fixed oils such as sweet almond, grape seed, peach kernel, olive and peanut oils etc. are basically odorless and used as carrier oils, massage oils and for use in food.The term essential oils is extended to Citrus oils even though they aren’t distilled because their constituents are mainly volatile, in fact, so volatile that they are regarded as Flammable (Hazardous Materials). Can I say it again? Do NOT use these on your face!
The original process for the production of Citrus essential oils was to cut the fruits into 2 halves, the fruit being scooped out and the hollow peels soaked in warm water. The thick inner pith absorbs water therefore swelling it plus making it resistant to cracking. The peels were then pressed against a small sponge one by one turning them inside out as they are pressed. The thickened and swollen piths thus apply pressure on the oil sacs rupturing them. The oil leaks or squirts out of the ruptured cells and is absorbed onto the sponge. The sponge is then squeezed out into a collecting bucket.
This method is labor intensive and although not widely used it is apparently still used for the finest Sicilian Lemon Oil. Modern mechanical methods have been designed to reproduce sponge pressing but maybe the oil produced is not quite as good as the purist demands.
Ecuelle a piquer method
The second method was to place the whole fruits into an inverted bell shaped container, lined with rows of spikes. As the fruits were turned in the container the spikes rasped the oil sacs in the outer peel of the fruits releasing the oil. The oil trickled down the inside walls of the container and collected in the bottom. Periodically the bottom was opened to allow the oil and peel debris to flow out. There are larger versions of this process designed for commercial production.
By-product of Juices
A third method comes under citrus fruit juice production rather than essential oil production. This is where the whole fruit is processed to produce the fruit and the oil is an unwanted by product that is separated and collected for sale. In terms of quantity this is by far the most important source of cheap oils such as Brazilian Sweet Orange Oil.
It’s important to know where your oils are coming from and how they were produced. It begs the question, does all-natural always mean safe? When it comes to essential oils, it depends on how you use them. They are not safe enough for us to use in our products, so we leave them out.