1. Water vapor evaporation method
The distillation method is one of the earliest refining methods used, and with the changes of the times, the utensils used have been significantly improved, but the principle is basically the same: the aromatic plants are placed in a distillation container, and then the high-temperature steam is passed into it (or the spices and water are boiled together), and the essential oils containing aromatic components in the plant will diffuse into the water vapor to form an azeotrope of oil and water; The azeotrope is then cooled, and since the oil is insoluble in water, it separates from the water to form the essential oil we need.
Distillation is very convenient and does not require the use of chemical solvents. Roses, lavender, rosemary, geraniums, etc., mostly use this method.
2. Pressing method (extrusion method or cold pressing method)
By cutting, crushing, extruding, etc., the water of the plant and the essential oil containing aromatic components are separated from the raw materials to obtain a mixture of water and oil, and then the oil and water are separated by centrifugation, filtration and other methods to obtain the essential oil.
In the past, this traditional way of extracting essential oils was common in the average household, which was not only simple and convenient, but also guaranteed that the natural composition of the essential oil was not destroyed during the extraction process.
Citrus, lemon, bergamot, lime and other plants will change their flavor in the high temperature of water vapor, and it is not suitable to use steam distillation, so most of them use this method.
3. Liposuction method (fat cold suction method)
The general method is to spread a layer of lukewarm fat (mostly butter or lard) in several flat-bottomed glass pots (or ceramic pots), and spread fresh flower petals on top of the fat; and cover the outer bottom surface of the basin with fat; These glass basins are then stacked on top of each other so that the petals are pressed between two layers of fat, and their oil can be absorbed by the fat. This way, the petals are replaced every day or two. until the fat is saturated. Finally, the fat is separated to obtain the essential oil.
This method is commonly used to extract essential oils such as jasmine, rose, and orange blossom.
Liposuction is an ancient method of extracting aromatic essential oils in southern France, and it is also the most expensive method due to the amount of labor and time involved.
4. Immersion method (oil warm soaking method)
This method is similar to liposuction, but with a simpler use of liquid grease:
When plant materials (petals, resins, etc.) are placed in liquid oil, heated and kept at a temperature of 60 to 70 degrees, the aromatic components in the raw materials are released into the liquid oil. Then the liquid oil is filtered and separated to obtain essential oil.
Frankincense, myrrh, sandalwood, etc. can all be used in this way.
5. Extraction method (dissolution method)
Liquid solvents such as alcohol and petroleum ether are fully mixed with plant raw materials, and the aromatic components in the raw materials, vegetable waxes, pigments, etc. will be dissolved and released into the solvent; The solvent is then separated from the liquid mixture, and an extract containing aromatic components, vegetable waxes, pigments, etc. is obtained; Finally, the extract is purified to obtain the essential oil.
This method is often used to refine essential oils from plants such as cinnamon, sage, benzoin, etc.
6. "Supercritical carbon dioxide" extraction
The principle is: the density of carbon dioxide at high pressure or low temperature is close to that of liquid, while retaining some properties of ordinary gases, which is called "supercritical fluid", which has strong dissolving ability. When the spice plant comes into contact with it, the aromatic components of the plant dissolve in this fluid. Then, by reducing pressure or increasing temperature, the aromatic components can be finally separated.
