Critical fluids were first discovered by Cagniard de la tourist in 1822 when the gases tested were trifluoromethane, ethane, nitrous oxide, sulfur hexafluoride, and propane. Finally, people choose carbon dioxide to extract volatile components (supercritical CO2 extraction), such as flavoring, making perfume and treatment, etc. This extraction method can also remove caffeine from coffee beans, extract cocoa butter, other types of vegetable oils, etc.
We know that ordinary carbon dioxide comes in two forms: solid dry ice and gas, but in any case, carbon dioxide does not exist as a liquid at normal atmospheric pressure.
If we set the pressure and temperature beyond the supercritical point (Tc and Pc), carbon dioxide becomes supercritical, dividing the two different ranges of gas and fluid solvent, so carbon dioxide becomes a dense liquid, but has gas properties, so when extracting plants, this liquid substance is not viscous and the surface is loose, but it can be thoroughly diffused.
Yes, supercritical carbon dioxide, a fluid-like substance, is like a liquid, with high density and good solubility. The higher the pressure, the better the solubility.
What can carbon dioxide extraction do?
Easily extractable components (up to 300 atmospheres) are lipophilic, have high vapor pressure (volatile) components, and low molecular weight (up to 400 Daltons), including iridoid hydrocarbons, alcohols, ketones, etc. ingredients, it matters.
At higher pressures and temperatures, triglycerides (vegetable and animal fats), wax fats (as in jojoba oil), and other heavier non-polar components can be extracted.
As mentioned above, CO2 can extract non-polar components in most cases. CO2 extraction looks like non-polar solvents, so things with magnetic polarity will reduce the extraction rate, so it is difficult to predict the results.
Such as sugars, glycosides, amino acids, lecithin, and alkaloids, which have magnetic polarity but cannot be extracted, the extraction range is very wide, so the carbon dioxide extraction method is not suitable for extracting all medicinal plants. It depends on the degree of solubility of the ingredients.
More polar substances can adjust the complex like you can add water to the extraction process to extract more polar complexes, most commonly seen from coffee alkaloid caffeine, or extract more from tobacco Nicotine, etc.
The method of carbon dioxide extraction
Using the supercritical CO₂ extraction method, the temperature is generally set at 40-60 degrees Celsius and the atmospheric pressure of 90-500.
For herbal medicine, this supercritical extraction method is important because it can extract aromatic plants, vegetable oils, antioxidants, complexes, and other therapeutic compounds, all of which cannot be extracted by steam distillation.
In addition, one of the main uses of liquid CO₂ extraction is to extract hop complexes that add flavor to beer.
Benefits of CO2 Extraction: CO2 Extraction VS Steam Distillation VS Solvent Extraction
The boiling point of highly volatile aromatic compounds is between 150°C and 200°C. If steam is distilled, it will be separated from other plant components, and they will condense after cooling, but at 100°C, water and oxygen will Change the structure of aromatic plant components, so the results will be different.
Some ingredients can be sensitive to heat, or even not at all. In other cases, various current proteins will break down, producing a so-called “artificial product”, and you can also become “decomposed products” such as hydrogen sulfide, ammonia, acetaldehyde, and others.
The acetic acid linalool is decomposed again, and it will return to the linalool and acetic acid of lavender essential oil. On the other hand, sesquiterpene lactones and leucohormone (above 80°C) are decomposed into sesquiterpene hydrocarbons, the dark blue sesquiterpene hydrocarbons of German chamomile.
That’s why Bulgarian Damascus rose oil is so expensive, and it doesn’t smell like a rose, because some of the ingredients have been changed back in the steam distillation process.
In the same situation, this distillation method is better for volatile components, such as monoterpenes (10 carbon atoms), and diterpenes (20 carbon atoms), the heavier the molecule, the relative, its boiling point and vapor The pressure will be higher, and therefore the heavier the molecules, the easier it will be to stay in the still.
The functional effects of plant essential oils, whether they contain high-quality volatile components or not, as long as the extraction is more complete, the effect will be more effective.
Some people use petrochemicals, such as solvents such as pentane and hexane, to extract flower progenitors. Hexane is a kind of high vapor pressure gasoline, which is highly volatile, flammable, and easy to explode. In the past 50 years, many plants have exploded in the process of hexane extraction, and finally burnt out, and all kinds of organisms are also destroyed. and died.
Hexane drifts into the atmosphere during its manufacture and handling, which inevitably causes serious environmental problems, although the use of state-of-the-art technology to produce equal-sized soybean oil is estimated to release about 88,000 kilograms of hexane per week to the atmosphere.
So in the end, although the final essence extracted with hexane works well, hexane will still remain in the original essence. The current European Union stipulates that in the prepared raw essence, the residual amount must be less than 10 parts per million solvent residual units. In practice this regulation allows only very small residues to be present (0.001% or less).
Carbon dioxide extraction can skip the above problems
Carbon dioxide extraction sets very low temperatures; there is no oxygen and no water. Therefore, there will be no so-called “decomposed products” or “artificial products”, so the extracted products can include the original ingredients of plants.
The hexane solvent extraction method can extract all the heavier and less volatile molecules, which does not seem to have any serious problems, but the residual solvent needs to be paid special attention.
After CO₂ extraction, the essential oil does not need to be further processed; however, the hexane-extracted condensate needs to be further processed to extract the more volatile and high-profile components.
The CO₂ extraction method is non-toxic, non-flammable, does not pose a danger to the environment, does not emit harmful substances, and does not produce toxic by-products.
The supercritical CO₂ extraction method has a unique ability to extract different components according to the needs. With atmospheric pressure of 80-100°C and temperature of 40-60°C, the main aromatic volatile components can be extracted. This is called “extract on demand”, which is roughly similar to the original essence extracted by hexane.
Using supercritical CO₂ extraction, increasing the atmospheric pressure by 200 to 500 can prolong the extraction cycle time and remove heavier lipophilic components such as waxes, triglycerides (vegetable oils), wax fats (such as charge joba oil), carotenoids, etc., these are called “total extracts” (full ingredients), which are somewhat similar to hexane-extracted condensates.
Medicinal uses of carbon dioxide extract
People will want to buy CO₂-extracted essential oils mainly because they can flavor and have perfume functions. In addition, some herbal and aromatherapy medical materials clearly explain the medicinal use of essential oils, and these essential oils can be easily purchased. get.
The CO2-extracted Calendula officinalis “all extracts” (Calendula officinalis) are a highly volatile triterpenoid monopoly, glycols, and esters, of which aspartic glycol monoesters are the most important (about 20% of the total). ), complexes like these are impossible to obtain by steam distillation since these are present in very low concentrations in hydroalcoholic (tinctures) and vegetable oils (infusion oils).
The CO2-extracted essential oil has about 180 times more volatile components than typical soaking oils.
Individual studies have shown that CO₂ extraction has better anti-infective power compared with general hydro alcohol tinctures, so the extract can also reduce infection. It is a powerful anti-infective drug, which can effectively reduce inflammation and relieve pain.
German chamomile is steam-distilled, and its essential oil will be greatly changed. German chamomile can appear dark blue because it contains sesquiterpene hydrocarbons, Marianne, a sesquiterpene lactone, and chromogenic. Matrice can be produced only after steam distillation and decomposition.
German chamomile extracted with CO2 retains the achromatic chamomile, which is an elegant and unique chamomile flavor, so it will look yellow-green.
This same special extract comes from German chamomile with the chemical type bisabolol, which has anti-infective and wound-protecting properties.
When it comes to anti-infective power, one study showed that achromatin has more anti-infective properties than matricide (10 times the former).
Steam distilled ginger essential oil is less active and lacks the pungent phenylpropane component, which means that the volatility is not high.
The ginger essential oil extracted by CO₂ contains 25% to 33% gingerol, gingerol, and ginger one, which is pungent and active ingredients. Therefore, the properties of ginger essential oil extracted by CO₂ are more active than ordinary ginger essential oil. Its composition It is more suitable for travel-related nausea, muscle soreness, cramps, arthritis, and other care products. Both Chinese and Western herbal medicines have roughly mentioned such usage.