Extraction and Yield
Methods of Extraction
Extraction and yield ….. Traditional methods of extraction include cold expression, distillation, enfleurage, extraction by solvents, and oil infusion. Distillation is the most common method.
This method uses cold pressure and is commonly used for citrus fruits. The oil is contained in the outer layer of the fruit peel and is removed by scrubbing. Using a centrifuge, the oil is then separated from the pulp.
Historians don’t agree on the origin of this process. The famous Arab alchemist, physician, and philosopher, Avicenna, is given credit by most. However, the Egyptians were probably aware of the primitive methods of distillation. Zozime, third century A.D. chemist wrote about many designs of still adorning the wall of a temple in Memphis.
This process uses a still, a distilling apparatus, consisting of a vessel in which a liquid is heated and vaporized and a cooling device or coil for condensing the vapor.
• 1. Heat source• 2. Still pot• 3. Still head• 4. Thermometer/Boiling point temperature• 5. Condenser• 6. Cooling water in• 7. Cooling water out• 8. Distillate/receiving flask• 9. Vacuum/gas inlet• 10. Still receiver• 11. Heat control• 12. Stirrer speed control• 13. Stirrer/heat plate• 14. Heating (Oil/sand) bath• 15. Stirrer bar/anti-bumping granules• 16. Cooling bath
Plants are contained in a vat or large cylindrical tank. Steam is directed through the plants from the bottom of the tank and evaporates the oils. The tank is covered with a special lid which collects the steam and directs it to the coils (usually refrigerated with running water) where the steam is condensed. The mixture of condensed water and oil separates naturally by decantation (pouring off a liquid without disturbing its sediment) in a Florentine vase.
Copper Still - France
Enfleurage and Oil Infusion
These two methods don’t allow for separation from the vegetable oil, but is well suited to creams, ointments, liniments, massage oils, and bath oils. In enfleurage a layer of fresh flowers is placed on an oil soaked cloth or a thin layer of lard. Every day the flowers are replaced by fresh ones until the correct concentration is achieved.
Oil infusion is perhaps the oldest method of extracting essential oils. Plants are soaked in a glass jar of vegetable oil exposing them to the sun for one to two weeks. The plants are strained out and more is added to the scented oil.
This method of extraction produces a product that can’t be used in aromatherapy because of the traces of solvent left behind. It’s a modern technique used to obtain a greater yield or for oils that can’t be obtained by any other method. Carnation, honeysuckle and jasmine are examples of oils that can only be extracted by this method. The plants are immersed in a solvent such as acetone. The separation is accomplished chemically by distillation under special temperatures that condense the oil but not the solvent.
Different plants give a wide range of yield of oil. This difference in yield leads to great differences in price. An oil that takes a great amount of plant will be on the expensive side while an oil that takes less plant will be less expensive. For example, to make one kilogram (kg) of lavender oil it takes 150 kg of lavender and to get the same amount of rose oil it takes 3,000 kg of rose. If you find oils in retail that don’t have a wide variation in price this is a warning that they aren’t pure essential oils but imitations.
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