CO2 extracts have gained significant popularity over the past decade across various industries, including food, fragrance, flavor, pharmaceuticals, food supplements, and cosmetics. Despite their widespread use, these extracts remain somewhat enigmatic—even for some retailers. So, if you find CO2 extracts puzzling, you're not alone!
Most of us recall from our school chemistry lessons that matter exists in three physical states: gas, liquid, and solid. These states are easy to grasp. However, when cosmetic chemists mention terms like "supercritical fluids" or "liquid crystals" in relation to CO2 extracts, these concepts may seem abstract and difficult to visualize.
If you’re struggling to understand CO2 extracts, keep reading—we’re here to clarify them for you.
What is an Extract?
CO2 extracts, as the name suggests, involve carbon dioxide gas. However, before diving into how they are made and why they are valuable in formulations, it’s important to first define what an "extract" actually is.
Unfortunately, there is no universally accepted definition for "extract" in cosmetic ingredient terminology, which can lead to confusion. Furthermore, extracts can be obtained through multiple extraction methods.
Common Extraction Techniques
One approach involves soaking plant material in oil for a few hours, days, or weeks before filtering it. To speed up the process, the plant material may be macerated (finely chopped) before infusion.
Alternatively, the extraction process can be enhanced using heat, mechanical agitation, ultrasound, or other energy sources to break down plant cells. While these methods yield extracts, the chemical composition of the final product can vary depending on the technique used.
Another method involves using a solvent that is later removed. This also results in an extract.
Some common volatile solvents for plant extraction include n-hexane, acetone, chloroform, methanol, and ethanol. The solvent is evaporated and re-condensed for reuse, leaving behind the plant extract, which is further refined based on the plant’s properties and intended application.
Hexane and ethanol extractions are widely used in the pharmaceutical, food, and cosmetic industries. While acetone, chloroform, and methanol are rarely used in consumer products, hexane remains a standard extraction solvent in conventional cosmetics and pharmaceuticals. However, organic formulations only permit ethanol extraction as an acceptable method for obtaining active ingredients.
How Does CO2 Extraction Work?
At room temperature, carbon dioxide (CO2) is a gas—famously linked to climate change, prompting industries to reduce their CO2 emissions. However, when controlled, CO2 is quite beneficial: it is colorless, odorless, non-toxic, and classified as Generally Recognized As Safe (GRAS) under FDA regulations. Additionally, it is affordable and readily available.
When compressed under specific conditions, CO2 behaves like a fluid, allowing it to dissolve non-polar substances with low molecular weight.
This process, known as Supercritical Fluid Extraction (SCF), offers several advantages over traditional extraction and pressing methods:
Operates at lower temperatures, preserving heat-sensitive compounds.
Prevents oxidation, maintaining the integrity of oxidation-sensitive components.
Provides greater selectivity and efficiency, resulting in higher yields and extended shelf life.
Is environmentally friendly and produces cleaner extracts.
Yields extracts with finer flavors and aromas compared to conventional methods.
However, SCF extraction also has some drawbacks:
It requires advanced technology and is more expensive than traditional maceration.
The resulting extracts often have intense coloration.
CO2 extracts tend to be more costly.
Components of CO2 Extracts
Supercritical CO2 functions as a lipophilic solvent, dissolving oil-soluble plant compounds such as volatile molecules (sesquiterpenes, monoterpenes, terpenols), triacylglycerides, tocopherols, tocotrienols, phytosterols, carotenoids, and squalene.
Although this list covers many key components, it does not encompass everything found in CO2 extracts. The exact composition depends on the plant material and extraction conditions, meaning CO2 extracts can resemble fixed oils (carrier oils), conventional extracts, or essential oils.
This overlap can create confusion. To complicate matters further, regardless of their chemical composition, all CO2 extracts are labeled simply as "extracts" in the International Nomenclature of Cosmetic Ingredients (INCI). For example, cinnamon CO2 extract is comparable to cinnamon essential oil, raspberry CO2 extract resembles raspberry seed oil, and calendula CO2 extract is similar to a calendula infusion in carrier oil. However, all three share the same generic "extract" designation, making it challenging for formulators to distinguish between different types of CO2-derived ingredients.
Comparing CO₂ Extracts with Traditional Extracts
To better understand the differences, let’s compare some CO₂ extracts with their conventional counterparts.
Cardamom Essential Oil vs. CO₂ Extract
Component | Cardamom Essential Oil | Cardamom CO₂ Extract |
INCI Name | Elettaria cardamomum seed oil | Elettaria cardamomum fruit extract |
Key Compounds | ||
Terpinyl acetate | 40.44% | 50.0% |
1,8-Cineole (Eucalyptol) | 29.90% | 25.40% |
Linalyl acetate | 5.02% | 6.30% |
Sabinene | 4.79% | 2.00% |
Linalool | 3.20% | 3.30% |
Limonene | 2.51% | 1.40% |
Myrcene | 1.96% | 0.41% |
Alpha Terpineol | 1.79% | 2.20% |
Alpha Pinene | 1.61% | 0.68% |
Geraniol | 1.11% | 0.72% |
Neral | 0.35% | 0.44% |
Geranial | 0.47% | 0.32% |
Evening Primrose Pressed Oil vs. CO₂ Extract
Component | Evening Primrose Pressed Oil | Evening Primrose CO₂ Extract |
INCI Name | Oenothera biennis oil | Oenothera biennis seed extract |
Physical Properties | ||
Density (20°C) (g/cm³) | 0.925 | 0.910–0.940 |
Refractive Index (20°C) | 1.4759 | 1.4760–1.4810 |
Saponification Value (mg KOH/g) | 193 | 193 |
Unsaponifiables | 1.7% | 3.5% |
Fatty Acid Composition | ||
Palmitic Acid (C16:0) | 6.3% | 6.1% |
Stearic Acid (C18:0) | 2.2% | 1.9% |
Oleic Acid (C18:1) | 7.2% | 7.1% |
Linoleic Acid (C18:2) | 73.3% | 74.5% |
Gamma Linolenic Acid (C18:3) | 8.9% | 9.7% |
Unsaponifiables | ||
Sterols | 0.96% | 0.94% |
Tocopherols | 770 ppm | 300 ppm |
Since CO₂ extracts can capture volatile compounds, they may contain allergens similar to those in essential oils. If their concentration exceeds regulatory limits, they must be listed on product labels. It's advisable to request an analysis or allergen list from suppliers before purchasing.
Comparing CO₂ Extracts with Macerated Oils
CO₂ extracts generally have higher potency than macerated oils due to differences in the extraction process.
Arnica Macerated Oil vs. Arnica CO₂ Extract
Component | Arnica Macerated Oil in Sunflower Oil | Arnica CO₂ Extract |
INCI Name | Helianthus annuus seed oil, Arnica montana flower | Arnica montana flower extract |
Key Active Compounds | ||
Triterpenediol Esters | 0.02% | 3–7% |
Helenalin Esters | 0.015% | 3.6% |
Sesquiterpene Lactones | 0.018% | 3.5–4.5% |
In macerated oils, plant materials are soaked in a neutral carrier oil and left to infuse for a period ranging from hours to weeks. Mild heat may be applied to improve extraction efficiency, but temperatures usually remain below 40°C. Given this method’s limitations, macerated oils contain significantly lower concentrations of active compounds compared to CO₂ extracts.
Final Thoughts on CO₂ Extracts
CO₂ extracts can resemble pressed oils, macerated extracts, or essential oils, depending on the plant source and extraction parameters. Despite their higher price, they offer superior quality, extended shelf life, and a lower required application dosage than traditional oils and extracts.
However, one major challenge lies in labeling: all CO₂ extracts bear the generic term "extract" in their INCI names. Without detailed information from suppliers, it can be difficult to determine the exact composition of an extract. Additionally, CO₂ extracts containing volatile compounds may carry fragrance allergens, similar to essential oils.
Ultimately, CO₂ extracts are a valuable addition to any formulator’s toolkit, offering a cleaner, more efficient, and higher-quality alternative to conventional extraction methods.
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