The essential oils of life
Plant wisdom have accumulated by people interacting with them initially as food sources but by eating plants their effectiveness as healing agents became obvious. Such wisdom allows plants to be harvested for their oils at their peak of production! Essential oils in plants have been under investigation for millenia!
The powerfully scented jasmine flowers can be used to extract the essential jasmine oil on the day the flowers open. Some plants are best harvested in the morning, some in the evening! It is only in recent years that we have begun to understand why plants produce their oils according to specific natural cycles.
Aromatic plants produce fragrant scented chemicals in special secretory cells, These are generally near to the surface of flowers and leaves. If you walk past these plants, brushing against them, this fragrance is released into the air.
In other plant species, touching them isn’t even necessary. They have mechanisms to release the chemicals into the air around them and the molecules which carry the aroma diffuse about through the air or are carried on the breeze. In other plants, the aromatic oils are produced within their transport system (akin to our circulation) or in root cells.
Collecting the Oils.
The essential oils are chemical molecules that carry the aroma. They can be extracted from plant material by a process called DISTILLATION. You may have even met this process in school chemistry lessons!
Distillation involves mixing chopped or ground up plant material with distilled (pure) water in a flask. If you heat this mixture, the heat will firstly cause the cells of the plant to burst, releasing any oils present into the mixture. However, oil and water don’t mix! The oils float to the top of the flask. The next part of the process depends on the boiling point of each oil compared to the boiling point of water.
Water boils at 100C. Some oils which are made from tiny molecules, boil at very low temperatures, below 100C. These oils are described as ‘very volatile’. If the mixture in the flask is heated up slowly, these very volatile oil molecule will escape from the flask and can be captured in a long water cooled tube called a condenser. The volatile oil turns back into a liquid in this tube and can be captured as it drips out of the end of the tube.
However in most cases, the volatile oils evaporate from the liquid and get mixed with the steam from the water. The steam condenses back to water as it passes through the water filled tube. This means that you are collecting a mixture of water and the essential oil. It is relatively easy to separate the oil that floats on the top of the water from the water itself.
The water itself, called the hydrosol, retains many of the therapeutic properties of the plant oil, making it an extremely valuable by-product for use in skin care or for facial mists and toners. In certain situations, floral water may be preferable to pure essential oil, such as when treating a sensitive individual or a child, or when a more diluted treatment is required.
Another method of extracting essential oils is by coldpressing. It is used to obtain citrus fruit oils such as grapefruit, lemon, lime, mandarin, orange, and tangerine oils. In this process, fruit rolls over a trough covered with spiky projections that penetrate the peel. This pops the cells containing the essential oil.
The whole fruit is pressed to squeeze the juice from the pulp and to release the essential oil from the pouches. The essential oil rises to the surface of the juice. It is then separated from the juice by centrifugation – whizzing the juice around in a centrifuge (a bit like a super fast mixer) at very high speeds.
Other methods such as Enfleurage, Solvent and Carbon Dioxide extraction are used to extract the oils where very delicate plant material is used. This method is also used where the oils are present in very low concentration or oils that would be broken down by heat.
You might think that each plant produces heaps of oil. You walk through a rose garden and the heady intensity of the rose perfume remains with you all day. One jasmine plants perfumes not just your garden but a large area around it!
However you need to remember that capturing those scent molecules is not that easy. It takes many millions of rose petals just to produce sufficient rose oil to fill one small 15ml bottle. The rarity or difficulty in extracting the oils is obviously reflected in its price.