The case for supercritical CO2
There are a number of methods for extracting botanicals. They include:
- Tinctures (usually alcohol extraction)
- Steam distillation
- Expeller pressing (sometimes called ‘cold pressing’)
- Chemical solvent extraction
- Supercritical CO2 Extraction
Our process brings the type of performance that each of these technologies offers in delivering various components of a botanical for use in consumer products. Each brings a level of effectiveness and cost to delivering the desired components that can be compared and evaluated. It should be noted that proceeding down the left axis, compounds are higher in molecular weight, and hence more difficult to extract. Different methodologies operate in different ranges. For example, tinctures deliver compounds from top notes through waxes, but do not extract some steam non-volatiles or the highest molecular weight compounds. Similarly, expeller press technology picks up some of the steam non-volatiles (not all) and some of the sterols, but is ineffective in delivering long chain alcohols and other high molecular weight compounds. From this graphic, it can be seen that chemical solvent extraction technology using strong solvents and supercritical CO2 technology using high pressures offer the most comprehensive extraction of a botanical. But even with these, there are trade-offs and areas of strengths and weakness that should be considered.
Supercritical CO2 Extraction
A relatively recent entry into the botanical extraction technology portfolio, supercritical CO2 extraction – often conducted under very high pressure – is becoming more widespread in use because of a number of important benefits that it offers. This is particularly the case in the production of high value/high efficacy nutraceuticals.
When carbon dioxide gas (CO2) is compressed above 73 bar at a temperature above 31° C (87.8° Fahrenheit) it transforms into a dense gas known as Supercritical CO2. Supercritical CO2 has an extremely high solvating capacity — the power to extract the constituents of botanicals. Because its solvating capacity is a function of its density, by changing its density (with pressure) we are able to select the quality, quantity and specific principles of the targeted extract.
Supercritical CO2 is biologically compatible, and generally regarded as safe (GRAS) by the FDA. It is non-flammable environmentally sound.
As Table 1 shows, extremely high extraction efficiencies are possible with this technology. The process is flexible and allows for fractionation of the product and the delivery of very specific compounds out of the raw material.
From a production standpoint, it is an environmentally friendly process and offers both worker safety and no disposal issues. Defatted cake resulting from the supercritical CO2 process is totally viable and can be marketed or used for further processing in a wide range of human/food applications. In fact, in many instances, the defatted cake is the primary product with the oil secondary. An interesting example of this is seen with chia seed extraction. After processing with supercritical CO2, the extract cake contains virtually no fat or oil. The resultant powder is approximately 50% protein and 50% carbohydrates that exist essentially as fiber. This type of product is considered ideal for a number of food applications.
From a product quality standpoint, it offers gentle treatment of high value raw materials at temperature levels substantially below those used in expeller press and some chemical solvent extraction operations, in the absence of oxygen. This reduces the degradation of labile compounds, chemical change of components and the oxidation potential. In addition, the nature of the supercritical CO2 process offers virtual sterilization of the finish product and biomass. Both of these end products are untouched by chemical solvents and stay as ‘natural’ as they were before extraction. Supercritical extraction using CO2 provides another big advantage in that it offers the ability to fractionate the extracted components very selectively. Pressure is the main tool used to tailor the resulting fractionated products for product quality and efficient manufacturing purposes. This also addresses the issue of pesticide/insecticide residues discussed earlier and at the same time handles concerns about microorganisms that might be present in expeller pressed materials. Another important product quality issue is the complete absence of chemical residues.
From a consumer standpoint, supercritical CO2 extracted products hit on a number of important trends. They can be marketed as all-natural and organic products. They are devoid of impurities and residues which can resonate with the safety concerns of consumers. Finally, they offer some of the highest efficacy profiles of any extracted products on the market. Supercritical CO2 delivers the high molecular weight compounds such as sterols, carotenoids and long chain alcohols that health studies point out as critical and that consumers want.