Throughout history, essential oils have been used for a variety of health care purposes. The Egyptians were the first to use aromatic essential oils. They used essential oils in a wide range of fields, from medicine, beauty, beauty, cooking, to religious ceremonies. Frankincense, sandalwood, myrrh, and cinnamon were all considered the most valuable goods in desert caravans and were sometimes even traded for gold.
Here, we’ll take a look at some essential oils extraction methods, and a few important processes and analyses for botanical and herbal essential oils extractions.
Essential oils, extracts, and absolutes
Essential oils are concentrated volatile oils — meaning they It evaporates quickly when exposed to air — derived from plant material. Most essential oils are lighter than water, with a few exceptions like cinnamon and bitter almond. This weight difference facilitates their separation after extraction.
Essential oil refers to the general term for volatile aroma-containing substances obtained by processing and extraction from spice plants or aroma-secreting animals. Generally, essential oils are volatile aromatic substances extracted from flowers, leaves, roots, seeds, fruits, bark, resin, wood heart, and other parts of plants. Essential oils are divided into diluted (essential oil blends) and undiluted (single essential oils) such as clove essential oil.
Essential oils are highly volatile and evaporate quickly once exposed to air, so essential oils must be stored in dark, airtight bottles.
A large volume of plant material is needed to produce essential oils, and their makeup can be complex, with hundreds of volatile components as It is mainly composed of terpenes, alcohols, phenols, aldehydes, esters, ketones, and other compounds.
Besides essential oils, extracts and absolutes are also products of extraction. Absolutes are the result of a more complex process using chemical solvents and evaporating or distilling to remove the solvent.
Extracts, on the other hand, are made up of phytochemicals left in a solvent (water, glycerin, and alcohol are common). Tinctures, which use alcohol as a solvent, are common extracts. Vanilla extract is a common example.
The different products have different uses, and many considerations go into selecting the most appropriate processing methods.
How to extract?
Influenced by the Greeks and Romans, the Persians learned the use of herbs from the Chinese and Indians and began to study how to improve the process of extracting essential oils. Essential oil extracts have been used throughout the dark ages of Europe for their protective and aromatic properties.
The production process is an important factor in improving the overall yield and quality of essential oils. The traditional method of essential oil extraction is the process of liquid/solid separation, which means adding the liquid to the solid feedstock and then separating the solids out of the solution. The traditional techniques for the processing of essential oils are of great importance and are still used in many parts of the world.
Water distillation, water, and steam distillation, steam distillation, reflux distillation, maceration, and liposuction are the most traditional and commonly used methods.
- When the distillation method has low oil yield, the impregnation method is suitable;
- Distillation is suitable for almond flour, rose petals, and rose petals;
- Solvent extraction is suitable for expensive, brittle, and thermally unstable substances such as jasmine, tuberose, and hyacinth;
- Hydrodistillation is the most popular method for extracting citronella oil from plant sources.
Over time, extraction methods have become more sophisticated, from soaking or fermenting plants in water to supercritical CO2 fluid extraction and beyond.
A while ago, in order to drink lemonade, I only needed to use half a lemon. I didn’t want to use the juicer. I squeezed the lemon juice directly with my hand. When I squeezed it with my hand, the essential oil from the lemon peel came to me at the same time as the lemon juice flowed down. After spraying, I immediately remembered the cold pressing method in the aromatherapy book. This is a purely manual cold pressing method. I also thought of this fresh lemon, there are so many essential oils!
The cold pressing method, as its name implies, is to press directly on the peel to squeeze out the essential oil in the peel.
Usually, the peel of citrus genus Rutaceae, such as sweet orange, lemon, grapefruit, tangerine, bergamot, etc., are rich in essential oils, and commercial mass-produced peel essential oils are usually produced at the same time. A lot of juice, so the citrus peels essential oil extracted by cold pressing is cheaper than other essential oils.
Let’s see how cold-pressed peel essential oil is made! A bunch of oranges jumped around on the machine lively, it turned out to be peeling, so interesting!
Distillation extraction is the most commonly heard method, and it is easy to find information in major books.
Today, I want to talk a little bit about the distillation method. If you want to distill and extract essential oils, you need a lot of experience and inheritance. Simple distillation equipment may only be able to distill pure dew. The extracted oil of each plant rate is also different. How much plant material is needed to distill a 10 ml bottle of essential oil? These skills require an accumulation of experience. If you can find seniors who are willing to teach and learn, I believe that you can take the road to failure less.
Distillation has a long history. The technology was originally used to distill high-concentration alcohol wine and later extended to the extraction method of plants. Now it is a common method of essential oil extraction on the market.
Distillation can be subdivided into water distillation, and steam distillation.
After crushing the plant material, it is boiled with water. In the closed distillation cylinder, the aromatic substances in the plant evaporate along with the water vapor and flow into the cooling tank with the pipeline. After cooling, it is reduced to liquid and flows into the collecting barrel.
This distillation method is more suitable for plants that will not be broken when boiled with water (it can be imagined as boiling soup to boil the essence of plants), such as woody and rhizome plants.
As the name implies, it uses hot water vapor to steam the plant material on the water (think of steamed buns with an electric pot). The volatile components in the plant will be taken away by the water vapor and flow into the pipeline through the pipeline The cooling tank, after cooling, is reduced to liquid and flows into the collection barrel.
This distillation method is suitable for more fragile herbs such as mint and leaf extracts.
After the liquid from the above two distillation methods flows into the collection barrel, the essential oil will float on the water due to its low density, and the lower layer will be pure dew. These two products have now become the products often used in aromatherapy.
Essential oils and hydrosols are distilled by the distillation method because, after heating extraction, the smell of essential oils and hydrosols is sometimes different from the original plants. For example, German chamomile flowers smell like sweet apples and chrysanthemums. After distillation, The essential oil that turns into blue smells like a thick herb with a touch of moist air so doesn’t be too surprised to smell the essential oil that is different from the original plant!
This is an ancient and traditional extraction method, which is complicated and labor-intensive. At present, only Grasse, the perfume capital of France, uses this technology to produce perfumes and balms.
- Prepare a long glass wooden frame (grease suction frame) and coat it with a layer of grease (usually solid, non-contaminated animal or vegetable oil)
- Arrange the fresh flowers one by one on the grease
- When the oil has absorbed the aroma of the flowers, replace it with a new batch of flowers, if repeated, until the oil has absorbed the aroma of the flowers (this oil is called “Pomade”)
- Then, the essential oil in the balsam is extracted with alcohol, and the alcohol is evaporated by low-pressure distillation to obtain “enfleurage absolute”
- This method reminds me of the current soaking oil, and the concept is also a bit similar. Soak the plant in vegetable oil, soak it directly, or heat it at low temperature for extraction, and use the oil to dissolve the essence of the plant, because it has recently entered the pit of handmade soap. , and also started soaking herbal vegetable oil by myself, very fun too!
Because of its high price, liposuction was gradually replaced by the solvent extraction method to be introduced next.
In the past, it was very popular to use 95% alcohol to soak the grapefruit peel (other citrus peels can also be used), and the alcohol solution after soaking was used as a dishwashing liquid. I have also tried it 😆, and now that I have learned aromatherapy, I don’t think it is so troublesome, also peeled and soaked, adding lemon essential oil is a time-saving and labor-saving method!
Later, after studying aromatherapy, I learned that the alcohol solution obtained in this way is called “tincture”. Maintenance and drinking; traditionally, sorghum wine is also used to soak traditional Chinese medicine, also known as “medicine wine”, and it is also a kind of tincture.
Solvent extraction is a gentle and meticulous extraction method because it has a relatively low degree of damage to essential oils. It is usually used on aromatic plants that cannot be distilled, such as:
- Unheatable Plant, ex Moroccan Rose
- Plants with low oil content, ex Chiba roses
- Contains resinous plant, ex benzoin
- The essential oils obtained by solvent extraction have a strong aroma, and even non-volatile substances (such as vegetable waxes and vegetable pigments) are also extracted with the essential oils.
- Place aromatic plants in airtight containers with organic solvents (such as ether, hexane, toluene, formaldehyde, acetaldehyde, alcohol, etc.)
- The solvent dissolves plant matter including essential oils, plant waxes, resins, plant pigments
- Then place the aromatic solvent in a vacuum steamer to evaporate the solvent to obtain a waxy “concrete”
- Use alcohol to extract the essential oil components in the condensed body, remove the wax, and then volatilize the alcohol to get the “absolute”
The aroma of the original essence is very close to the aroma of the original plant, but no matter how the solvent is evaporated, there will still be a little organic solvent left in the original essence. Please pay attention to low-dose use, as it may cause skin irritation.
Carbon dioxide extraction
At medium temperature and high pressure, carbon dioxide will reach a critical point, appear in the state of liquid and gaseous supercritical fluid, and become a medium with high solubility, so it can extract plant essential oils and other components.
Put the plants in a closed high-pressure reaction tank
Carbon dioxide supercritical fluid passes through plants, bringing out the aromatic molecules and essence of plants
Reduce the pressure, let the carbon dioxide change back to a gas, and get pure CO2 essential oil
This extraction method has several advantages:
- The aromatic molecules are complete, not damaged by high temperature, and it is easy to obtain the complete components of the plant
- Short extraction time and high oil extraction
- Carbon dioxide does not easily react chemically with the aromatic molecules of essential oils
- The smell of essential oils is close to the original plant smell
- CO2 extract is usually darker in color and stronger in smell.