Application of Supercritical CO₂ Technology in Essential Oil Extraction
Along with social development, essential oils have become an important source of raw materials. With their practical uses, essential oils have long been regarded as “nature’s treasures” due to their rich composition of bioactive compounds applicable in human life. Today, scientists have developed essential oils into widely used raw materials for therapy, healthcare, food and beverage flavoring, as well as in the global production of perfumes and cosmetics.
To separate essential oils from aqueous mixtures, various extraction methods have been employed, among which supercritical CO₂ extraction technology produces natural, solvent-free, and environmentally friendly essential oils.
Advantages of the Technology
Matter exists in three basic states: solid, liquid, and gas. Under specific conditions, when a gas is compressed to its critical pressure (Pc), it condenses into a liquid. If the temperature is then increased to its critical temperature (Tc), the liquid cannot revert to a gaseous state but instead enters a unique phase known as the supercritical state.
Due to its low critical parameters, availability, low cost, non-corrosiveness to equipment, and its ability to evaporate completely under ambient pressure without leaving solvent residues, carbon dioxide (CO₂) is commonly used as the solvent in supercritical fluid extraction (SFE).
When CO₂ is brought above its critical temperature and pressure (Tc = 31°C, Pc = 73.8 bar), it becomes supercritical CO₂, exhibiting intermediate properties between gases and liquids. In this state, it shows excellent solubility for target compounds.
According to Dr. Mai Thanh Chi from the Institute of Chemical Technology, Vietnam Academy of Science and Technology, during the extraction process, once the pressure is reduced below the critical point, CO₂ reverts to a gaseous state and escapes, leaving behind pure, natural essential oils as the final product.
Historical and Technical Overview
Historically, humans have extracted essential oils for daily use through various methods such as classical steam distillation, solvent extraction with volatile organic solvents, and techniques assisted by microwave or ultrasound.
However, compared with traditional techniques, supercritical CO₂ extraction offers several outstanding advantages:
• Produces high-purity products of superior quality.
• Retains the natural aroma and composition of essential oils.
• Preserves bioactive compounds.
• Eliminates solvent residues.
• Allows separation of components at high concentration levels.
• Is environmentally friendly and non-polluting.
Applications in Essential Oil Extraction
Due to its ability to produce safe and natural products, supercritical CO₂ extraction is now widely applied in isolating natural compounds across various industries. This technology is used to extract bioactive substances from herbal materials for use in pharmaceuticals, health supplements, cosmetics, and biotechnology.
In the perfume industry, it enables the extraction of rare and delicate essential oils for producing high-end fragrances as well as flavor compounds for the food and beverage sectors.
Globally, supercritical CO₂ technology has been industrially applied in several areas:
• Extraction of cosmetic-grade essential oils from hops and herbs (New Zealand, Poland).
• Decaffeination of coffee and tea (Germany, Italy).
• Extraction of spice and herbal essential oils (India).
• Removal of pesticides from rice (Taiwan).
• Extraction of sesame oil (Korea).
In Vietnam, supercritical CO₂ extraction has been successfully applied for the production of agarwood oil, chamomile oil, gac oil, pepper oil, cinnamon oil, and others.
Conclusion
The application of supercritical CO₂ extraction technology in essential oil production is an emerging trend that ensures consumer safety and environmental sustainability. With its technological advantages, it represents a promising and innovative approach for industries involved in the production and processing of natural herbal products.
