Steam distillation: Steam distillation is the earliest refining method. With the change of the times, the equipment used has been obviously improved, but the principle is basically the same: put the aromatic plants into a distillation container, and then introduce high-temperature steam into it (or boil the spices with water). At this time, the essential oil containing aromatic components in plants will diffuse into the steam, forming a boiling substance of oil and water; After that, the boiling substance is cooled, and because oil is insoluble in water, it is separated from water to form the essential oil we need. Distillation is very convenient and does not require the use of chemical solvents, so it is still widely used. Rose, lavender, rosemary, geranium, etc. This method is mostly used. Squeezing method (squeezing method) separates water and essential oil of plants containing aromatic components from raw materials by cutting, crushing, squeezing and other methods to obtain water-oil mixture, and then separates oil and water by centrifugation, filtration and other methods to obtain essential oil. In the past, ordinary families used this traditional way to extract essential oil, which was not only simple and convenient, but also ensured that the natural components of essential oil were not destroyed during the extraction process. Citrus, lemon, bergamot, lime and other plants will taste bad at the high temperature of steam, so steam distillation is not suitable, so this method is often used. The general method of fat absorption (fat cold absorption) is: spread a layer of lukewarm fat (mostly butter or lard) in several flat-bottomed glass basins (or ceramic basins) and sprinkle fresh petals on the fat; The bottom surface of the outside of the basin is also covered with grease; Then these glass basins are stacked layer by layer, so that the petals are pressed between the two layers of fat, and the fat can be absorbed by the fat. In this way, change the petals every one or two days. Until the fat is saturated. Finally, the fat is separated to obtain the essential oil. This method is often used to extract essential oils such as jasmine, rose and neroli. Liposuction is an ancient method for extracting aromatic essential oil in southern France. Because it takes a lot of manpower and time, it is also the most expensive method. Soaking method (warm oil soaking method): this method is similar to fat absorption method, but it is simpler to use liquid oil: plant raw materials (petals or resin, etc.) are added. ) In liquid oil, heating and keeping the temperature at 60 to 70 degrees will release the aromatic components in the raw materials into the liquid oil. Filtering and separating the liquid oil to obtain essential oil. . This method can be used for frankincense, myrrh and sandalwood. Leaching method (dissolution method): liquid solvents such as alcohol and petroleum ether are fully mixed with plant raw materials, and aromatic components, plant wax and pigments in the raw materials will be dissolved and released into the solvent; Then separating the solvent from the liquid mixture to obtain an extract containing aromatic components, vegetable wax, pigment and the like; Finally, the extract is purified to obtain essential oil. This method is often used to extract essential oils from cinnamon, sage, benzoin and other plants. The principle of "supercritical carbon dioxide" extraction method is that the density of carbon dioxide is close to that of liquid at high pressure or low temperature, while retaining some properties of ordinary gas. Solids are called "supercritical fluids", which have strong solubility. When an aromatic plant comes into contact with it, the aromatic components of the plant will dissolve in this liquid. Then the aromatic components can be finally separated by decompression or heating. This is a new method that has appeared in the world in recent years. This method can make the extraction of essential oil at room temperature, without using solvents harmful to human body, and can better protect the natural activity of products. It is an advanced "green separation technology". Traditional separation methods, such as steam distillation, squeezing and leaching, all have some shortcomings in the processing, such as the natural effective components are easy to be destroyed, and organic solvents harmful to human body may remain in the final product. However, the cost of this method is still high and it has not been widely used. References:

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