Resolve popular concepts in the field of aromatic plant extraction

With the continuous spread of the concept of aromatherapy, more and more people are beginning to understand essential oil products, and the concept of naturalness is also deeply rooted in the hearts of the people. It is not difficult to find that with the rise of the Internet, various kinds of information have sprung up into consumers’ cognitive systems, and various concepts have continued to innovate. Then small extraction devices have also entered the lives of ordinary people, and the Internet of Things has become more and more developed. From small studios to large factories, hydrosols and essential oils are produced. The quality of the products varies from good to bad. Various disputes seem to occur every day. This article clarifies common controversial concepts and phenomena for your reference.

Primary concepts in the field of aromatic plant extraction

Essential oil

Plant roots, stems, leaves, branches, stems, flowers, fruits, seeds, as well as secreted oils and sap are separated by physical methods such as distillation or squeezing to prepare oily substances with characteristic aromas.


It is secreted by specialized secretory cells in the plant. These secretory cells may be present in leaves, bark or other parts. The essence of plants can be directly stored in secretory cells, or transported to storage vesicles or storage tubes for storage. In short, essence is the unprocessed aromatic substance that exists in the plant.


The aromatic substance obtained by the solvent extraction method is called the condensate (extract). The condensed body contains essential oils, fats and waxes, which are treated with absolute ethanol to obtain the original essence (absolute oil/absolute oil). When the steam distillation method destroys plant ingredients, this method is chosen to extract plant essences, such as jasmine.


The picked flowers come into contact with the fatty substances, and the flowers are replaced after 24 hours to absorb the fat whose fragrance components have reached the saturation level. This fatty substance is balsam, and the jasmine balm we often say is balsam.

Some oils in aromatherapy are not extracted by distillation, but are extracted by liposuction or solvent extraction. The final substance extracted by this method is called the original essence, absolute oil or absolute oil.

Using liposuction, a substance called “balsam” can be obtained, which is a mixture of lipids and essential oils.

Using the solvent extraction method, a layer of mixed balsam body is obtained, including lipids, waxes, essential oils and other plant substances. After treatment with anhydrous alcohol, the original essence can be extracted from the balsam or balsam body ( Net oil/absolute oil).

The difference between essential oil and essence

Essential oil and essence are not the same concept. The influence of temperature, air and steam in the distillation process changes the chemical composition of the essence. The chemical composition of the final essential oil is already different from that of the aromatic plant, such as German chamomile.

Selection Basis of Aromatic Plant Extraction Method

Heat sensitivity of key ingredients

Whether the high-temperature contact of aromatic plants and water vapor destroys the key aromatic substances is an important basis for selecting distillation methods.

Citrus peel

The composition of citrus oil is easily destroyed in the distillation process, and most of it is obtained by pressing, except for lime and bitter orange fruit extraction.


When steam distillation, the ingredients are easily destroyed. Generally, it is prepared by solvent extraction or cold absorption. In recent years, with the improvement of technology, there are some market-produced supercritically extracted lily flower essential oils. The smell is very close to that of fresh flowers. breath.


Both steam distillation and volatile solvents can obtain high-quality rose extracts, and the distillation method is less costly and easy to operate, so this method has been used to extract rose essential oil, and the solvent extraction method can be made into rose extract (rose extract). Absolute oil), the aroma extraction is relatively complete, closer to the aroma of the rose itself; the cold suction method can also produce rose balsam (rose flower ointment), and there are also supercritically extracted rose essential oils, but they are not commercially produced.

Volatility of aromatic substances

Aromatic plants such as musk, vanilla, black couma, and benzoin cannot be distilled out of their aroma components by distillation.

Cistus candidum can only extract a very small amount of essential oil by steam distillation, while solvent extraction method not only has a high yield, but also can extract valuable aroma components from it.

Comprehensive conditions of origin

The world’s large-scale planting of aromatic plants is concentrated in developing countries. Due to technology and equipment constraints, most of them are extracted by traditional distillation and exported to developed countries in the form of raw oil for finishing.

In my country, with the improvement of environmental protection requirements, traditional heating methods such as coal or burning straw have been gradually replaced by electricity and gas heating methods. At the same time, as labor costs increase, processing companies are developing in the direction of finishing, and the planting area is gradually shrinking. Supercritical and subcritical extraction methods have moved from the laboratory to industrial production, and are increasingly used in the high value-added fragrance industry.

The main extraction methods of rose essential oil


The main volatile aroma components of rose are citronellol, nerol, and geraniol (about 40% or more). They are volatile and hard to dissolve in water. They can be extracted by steam distillation. The factory chooses the method of pre-treating roses according to the equipment and processing capacity. The equipment is larger, and the flowers are distilled in the full blooming period. If it is too late to process the same day, most of the factories will use the salting method to extend the shelf life, and the salting can also increase the oil. At the same time, some factories concentrate the salted Damascus roses and distill them after the picking season.

Rose wax, the waxy component on the petals of Damascus rose, will enter the essential oil with steam during distillation, and will quickly condense into crystals in the bottle at low temperatures (16-22°C). This phenomenon does not appear in the solvent-extracted Damascus rose essence, because the rose wax is washed off by the solvent during solvent extraction, and it does not appear in the essence of French perfume rose or other rose varieties. in. The property of crystallization at low temperature cannot be used as the only criterion for testing the authenticity of the essential oil of Dama leather rose. For example, Huohuoba oil also crystallizes at low temperature.

It is generally believed that extraction by distillation can only obtain volatile aromatic substances that are insoluble in water, with the exception of phenethyl alcohol, which often appears in rose essential oil prepared by reflux distillation, and also gives rose essential oil a fragrance closer to flowers.

Special processing technology: reflux distillation method

The rose essential oil prepared by reflux distillation contains phenethyl alcohol, which is a colorless, rose-scented, and water-soluble component. Otto Rose is not a rose variety name, but a special processing technique of a specific variety (Damascus rose). In the production process of Otto Rose, when the rose petals are distilled, a large amount of phenylethyl alcohol will be dissolved in distilled water. In the process of repeated distillation, the first distilled water will be collected and returned to the distiller for re-distillation, and the separated Phenyl alcohol will be collected again and returned to the original distiller, so Otto rose essential oil contains water-soluble aromatic substances-phenyl alcohol.

Otto Rose

Otto Rose is a mixture of Decanted oil (first program) and recovered oil (second program) essential oils.

1. Distill the Damascus rose in water, collect the distilled water and oil, and separate the first process essential oil (Decanted oil).

2. Pour the water distilled out for the first time back to the distiller for re-steaming. After oil-water separation, the recovered oil produced by the second process is obtained.

3. Finally, the Decanted oli produced in the first process and the recovered oil produced in the second process are mixed together, and then subjected to a special maturation technology (fermentation) to finally make Otto rose essential oil.


Organic solvent method

Production principle: Similar to the principle of compatibility, the volatile aromatic substances in the rose are brought out by the volatility of organic solvents.

Material handling: flowers are generally used.

Extract properties: yellow-green waxy solid (extract), red-brown absolute.

Sensory evaluation: close to the smell of flowers, the top fragrance remains intact.

Advantages and disadvantages: simple operation, low cost, and fragrance close to flowers. However, a large amount of volatile solvents (environmental pressure) are used, and there are pigments and solvent residues.


Supercritical-CO2 extraction method

Production principle: The use of carbon dioxide gas has a dissolving ability similar to that of liquids in a supercritical state, while maintaining the special physical properties of the gas to separate and extract substances.

Material handling: dried flowers are generally used.

Extract properties: reddish brown viscous liquid.

Sensory evaluation: the top incense is well preserved and the aroma is complete.

Advantages and disadvantages: low extraction temperature, no solvent residue, high extraction rate, short extraction time. However, it can only be carried out under an ultra-high pressure above 25MPa. The extremely high pressure limits the effective volume of the equipment, and the equipment cost and start-up cost are high, and the production capacity cannot keep up with the actual demand.


Subcritical extraction

Production principle: Taking subcritical fluid or a mixed solution of subcritical fluid as solvent, and solute in the system successively through the processes of leaching, evaporation and desolvation, compression, condensation and recovery, extracting one of the target components from natural products Kind of new technology.

Material handling: fresh petals.

The extract is rotten: reddish brown viscous liquid.

Sensory evaluation: the top incense is well preserved and the aroma is complete.

Advantages and disadvantages: non-toxic, harmless, environmentally friendly, non-polluting, retaining the active ingredients of the extract without destroying or oxidizing, large production capacity, industrial large-scale production, energy saving, low operating cost, and easy to separate from the product.


Purification by molecular distillation

Production principle: The production principle of molecular distillation purification method is to use different kinds of liquid molecules to complete the separation by using the different straight-line distances after being heated from the liquid surface.

Molecular distillation: Also called short-path distillation, it is a method of high-efficiency separation and purification.

Main function: Molecular distillation purification method is mainly used to purify the initial extract (crude oil) obtained by solvent extraction, supercritical extraction, subcritical extraction and other methods.

Advantages and disadvantages: low temperature and very short residence time (about ten seconds). The separation process will cause very little thermal damage to materials. It is especially suitable for effective and non-destructive separation of high boiling point and heat sensitive substances, but the equipment is expensive.