Terpenes are natural compounds found in numerous plants, giving them their characteristic aromas and flavors. In nature, these compounds play important roles for plants, such as attracting pollinators, repelling predators, and contributing to plant defense mechanisms. Beyond their ecological functions, terpenes are valued across various industries. They are widely used as fragrances and flavors in consumer products, including perfumes, cosmetics, cleaning agents, and food and drink items. Some terpenes are also explored for potential pharmacological effects and are components in traditional medicines like aromatherapy. Their widespread utility makes effective extraction a significant area of focus.
Key Principles of Terpene Extraction
Terpene extraction involves separating these aromatic compounds from the rest of the plant material. This process aims to isolate terpenes while preserving their delicate structures and aromatic profiles, as they are sensitive to heat. Extraction methods can be categorized into two main approaches: solvent-based and solventless techniques.
Solvent-based methods use a liquid solvent to dissolve terpenes from plant material. The solvent is then removed, leaving a concentrated extract. Solventless methods use physical processes like heat or pressure to separate terpenes without chemicals. These approaches differ in principles and extract characteristics.
Common Terpene Extraction Techniques
Steam Distillation
Steam distillation is a traditional method for extracting volatile compounds like terpenes from plant material. This technique involves passing steam through the plant, which causes the volatile terpenes to vaporize. The vaporized mixture of steam and terpenes is then cooled in a condenser, turning back into liquid form. The resulting liquid, an oil and water mixture, separates due to differences in density, allowing the less dense terpene-rich oil to be collected.
This method uses a steam generator, an extraction vessel, a condenser, and an oil/water separator. It produces organic, solvent-free products and is simple and inexpensive to scale. However, high temperatures can degrade heat-sensitive terpenes, leading to lower yield and altered profiles.
Solvent Extraction
Solvent extraction uses a liquid solvent to dissolve and separate terpenes from plant material. Common solvents include ethanol, butane, and propane, each interacting with plant compounds differently. The plant material is submerged in the solvent, allowing the terpenes to dissolve into the liquid.
Ethanol is used to dissolve terpenes and other compounds. While efficient and safe, ethanol can also extract unwanted substances like chlorophyll, which may require additional refinement. To mitigate chlorophyll extraction, some processes use cold ethanol, reducing the solubility of these undesirable components.
Butane and propane extraction use these gases under pressure as liquid solvents. This method efficiently extracts terpenes and produces potent profiles, often at low temperatures to preserve compounds. However, hydrocarbons are flammable, requiring specialized equipment and safety protocols. Closed-loop systems recover and reuse the solvent, improving efficiency.
CO2 Extraction (Supercritical Fluid Extraction)
CO2 extraction uses carbon dioxide in a supercritical state, exhibiting properties of both a gas and a liquid. This state is achieved by applying temperature and pressure to CO2. The supercritical CO2 acts as a solvent, passing through the plant material to dissolve terpenes and other compounds.
After extraction, the pressure is reduced, causing the CO2 to revert to a gaseous state and separate from the extracted compounds, which are then collected. This method is tunable, allowing operators to adjust pressure and temperature to selectively extract specific compounds and preserve delicate terpenes. This allows versatility in creating different types of extracts, from terpene-rich oils to more isolated compounds. CO2 extraction is considered clean and safe as CO2 is non-flammable and leaves no residual solvent.
However, the equipment involves a high initial investment, and the process can be time-consuming. Managing fluctuating temperatures and pressures for optimal results adds to operational challenges.
Mechanical Separation (e.g., Rosin Press)
Mechanical separation methods physically extract terpenes without chemical solvents. The rosin press is a prominent example, using heat and pressure to squeeze terpene-rich resin directly from plant material. This involves placing plant material, like hash rosin, between heated plates and applying force.
Heat and pressure cause terpenes and other oils to liquefy and separate from the solid plant matter for collection. This technique is popular for producing solventless concentrates known for their purity and rich flavor. Mechanical separation produces solventless extracts, often considered purer, and preserves a more complete terpene profile with minimal chemical alteration. However, this method can be less efficient in yield than solvent-based techniques and requires careful temperature control to avoid degradation. Overheating degrades volatile terpenes, compromising aromatic quality.
Optimizing Terpene Extraction Outcomes
Optimizing terpene extraction involves careful attention to factors beyond the chosen method, influencing the final product’s quality. The quality of raw plant material is a key factor, as genetics, growing conditions, harvesting time, and proper drying and storage affect the terpene profile and concentration. Properly prepared biomass, like well-cured and ground material, contributes to better yields and purer results.
Achieving purity is important, ensuring the extract is free from contaminants like residual solvents, waxes, or chlorophyll. While higher yields are desirable commercially, a balance must be struck with quality. Aggressive parameters can degrade delicate terpenes, sacrificing integrity for quantity. Preserving the full terpene profile means prioritizing lower temperatures and gentler processes to prevent thermal degradation.
Post-extraction handling and storage are important for maintaining terpene integrity. Terpenes are volatile and sensitive to heat, light, and oxygen, so proper storage in cool, dark, and sealed containers helps prevent degradation and preserve aroma. Safety is paramount in any extraction environment. This includes proper ventilation, handling flammable solvents with strict protocols, using personal protective equipment, and adhering to facility design standards to mitigate risks from high pressures or hazardous chemicals.