The Science of Chill: How Temperature Affects the Ethanol Extraction Process

Ethanol extraction is a versatile process that involves using ethanol as a solvent to separate desired compounds from plant material. It’s widely used within the cannabis industry due to its ability to dissolve many compounds, including essential oils, cannabinoids, and terpenes, and produce high-purity extracts. It’s also highly scalable, making it ideal for larger operations, and is generally safer to handle and less flammable than other solvents.

Although ethanol extraction is a commonly used method, it’s important to note that this doesn’t mean it’s easier to execute. Compared to other extraction methods like CO2 and hydrocarbon, ethanol extraction requires extreme control as temperature can impact the final extract’s quality, efficiency, and nature. The process typically spans from sub-zero temperatures to about 173 degrees Fahrenheit. However, using cooler temperatures (sometimes known as chilled ethanol extraction) is more common as it helps preserve volatile compounds like terpenes and minimize the extraction of undesirable waxes and chlorophyll.

In this article, we’ll discuss how temperature impacts various factors in the ethanol extraction process, including solubility, extraction rate, compound selectivity, ethanol evaporation, viscosity and density, and thermal degradation.

Solubility

emperature can significantly influence the ability of the compound to dissolve in ethanol. The basic principle in chemistry is that solubility generally increases with temperature due to the increased kinetic energy that molecules have at higher temperatures, which helps overcome the forces keeping the compound in its solid or original form.

So, raising the temperature can increase the rate at which compounds dissolve in ethanol, leading to a more efficient extraction process. It’s also important to note that different compounds have varying solubility profiles. Adjusting the temperature makes it possible to target specific compounds more selectively.

For example, cannabinoids are relatively stable and become more soluble in ethanol at higher temperatures. In contrast, terpenes are extremely volatile and can be lost at higher temperatures due to evaporation or degradation. Higher temperatures will also result in the extraction of chlorophyll and fats, which impact the end product’s flavor, color, and purity. Lastly, higher temperatures increase the solubility of non-polar compounds like neutral cannabinoids (THC and CBD).

Using cold ethanol (often at sub-zero temperatures) is generally common because it reduces the solubility of unwanted components, which require additional purification steps.

Extraction Rate

The extraction rate is influenced by several factors, one of the most significant being temperature. At higher temperatures, the kinetic energy of the molecules in ethanol and the plant material increases, leading to more frequent and forceful collisions between solvent molecules and the compounds that will be extracted, which increases the extraction rate.

Although higher temperatures will result in faster extraction, it’s important to consider the potential risks of using too high a temperature during extraction. These risks include:

• Degradation: Some compounds, especially terpenes, are sensitive to heat and can degrade at higher temperatures, which impacts the potency and profile of the final extract.
• Ethanol Evaporation: Ethanol has a low boiling point (approximately 173 degrees Fahrenheit). At temperatures near or exceeding this boiling point, ethanol can evaporate and pose unnecessary danger and risks.
• Extracting Unwanted Compounds: As mentioned earlier, chlorophyll and waxes are not desirable in end products, but higher temperatures often mean that these compounds will be extracted, which means you will need to perform additional purification steps.

Compound Selectivity

As mentioned in the previous section, different compounds have unique solubility profiles that determine how easily they dissolve in ethanol at different temperatures. By experimenting, you can determine which temperatures best extract certain compounds.

Temperature also impacts vapor pressure and volatility of compounds. If extracting volatile compounds like terpenes, lower temperatures can prevent evaporation and loss during extraction. Comparatively, higher temperatures may result in the loss of terpenes but the extraction of more stable compounds.

Let’s break down some of the most common compounds:

• Cannabinoids: The optimal temperature range for extracting neutral cannabinoids like THC and CBD typically falls between -4 degrees and 86 degrees Fahrenheit. Many cannabis companies will use sub-zero temperatures to minimize the extraction of waxes and fats.
• Terpenes: A lower temperature range is preferred, ideally below 68 degrees Fahrenheit, because terpenes are extremely volatile and sensitive to heat.
• Flavonoids: Flavonoids are stable compounds with a similar temperature range as cannabinoids.
• Fats, Waxes, & Chlorophyll: Higher temperatures increase the solubility of these compounds, so if you want to avoid extracting them, perform the extraction process in a sub-zero temperature range.
• Acidic Cannabinoids (THCA, CBDA): The extraction temperature should be kept low (under 86 degrees Fahrenheit) to prevent decarboxylation.

Ethanol Evaporation

As we’ve already established, ethanol has a low boiling point and will evaporate significantly once temperatures are near or exceed its boiling point. Ethanol evaporation can impact the concentration and composition of an extract, so it’s important to reduce solvent evaporation during the extraction process. Evaporation is also a safety concern as ethanal releases flammable vapors.

To minimize evaporation, conduct the extraction process below boiling point (173 degrees Fahrenheit) and consider using a closed system and/or a solvent recovery system to reduce ethanol loss.

Changes in Ethanol’s Viscosity & Density

When temperatures increase, ethanol becomes more fluid/less viscous and can efficiently extract certain compounds faster and more uniformly, which can be ideal for large-scale operations. Ethanol’s density will also decrease as the temperature increases. The lower density affects the solubility of certain compounds and post-extraction separation efficiency.

In addition to finding the optimal temperature, it’s important to invest in the right equipment to accommodate potential changes in ethanol’s viscosity and density.

Thermal Degradation

Thermal degradation is always a concern during ethanol extraction, particularly when dealing with heat-sensitive compounds like myrcene, limonene, linalool, beta-caryophyllene, terpinolene, THCA, CBDA, and CBCA. When exposed to high temperatures, terpenes can lose their aromatic qualities, while cannabinoids may undergo decarboxylation.

Identifying the optimal temperature range that is high enough to ensure efficient extraction but low enough to prevent significant degradation is critical. For many compounds, this involves maintaining temperatures well below their boiling point and sometimes using refrigerated or cryogenic ethanol extraction processes.

Choosing the Optimal Temperature

There is no standard “optimal” temperature for the ethanol extraction process, as the temperature you use will vary depending on the type of end product you’re making and your desired extraction rate and efficiency goals.

Generally, using a sub-zero temperature range or “chilled ethanol” process is common because it results in higher-quality end products that require fewer post-extraction purification steps, but it will slow down the extraction rate.

Some cannabis companies that want higher extractions may conduct ethanol extraction at higher temperatures while using controlled heating systems, solvent recovery systems, and various post-extraction processing methods, like distillation, to ensure better purity in the end product.

So, determine your operational goals and go from there. Here’s a table that breaks down some of the most common goals:

Goal	Temperature Requirements
Preserving Volatile Compounds	Lower temperatures are needed.
Maximizing Yield/Better Efficiency	The higher the temperature, the higher the extraction rate.
Avoiding Fats, Waxes, & Chlorophyll	Lower temperatures, particularly sub-zero temperatures, will prevent the extraction of these compounds.
Higher Purity	Lower temperatures are required.

Again, if you’re targeting specific compounds, the best method is to experiment until you find the right temperature range for those unique compounds.

Learn More From MACH Technologies

Finding the right temperature for your extracts is just one step of the process—you also need to invest in the right equipment.

That’s where MACH Technologies can help.

We’re a specialized equipment manufacturer that engineers fully automated cannabis extraction equipment. Our line of ethanol extraction equipment includes MDT ethanol chilling systems, stand-alone extraction units, particle filtration systems, the ASR automated solvent recovery system, the DS decarboxylation reactor system, and the wiped film distillation system. We also manufacture the EES, a fully automated and integrated ethanol extraction solution that includes cryogenic ethanol extraction equipment, an automated solvent recovery system, and an automated decarboxylation system.

Our solutions are manufactured in-house in Michigan and comprehensively tested for safety. Our equipment also features ASME-certified pressure vessels and UL-approved electronics to ensure safety, quality, and compliance.

Please contact us today to learn more about our solutions. Our experts can not only help you find the right equipment but also provide implementation assistance, including installation and training, and long-term technical support.