Supplementary Solventless Terpene Extraction with a Freeze Dryer

Terpene extraction is an optional step you can take to make full use of the hydrosol you capture from your freeze dryer during the hash freeze drying process and use every last “part of the buffalo” in terms of your cannabis flowers. 

“Hydrosol” is a water-based product made from the water or steam distillation of plant matter, and with a couple of extra—relatively simple—steps involving cold temperatures and time, you can separate the essential oils (the oils that contain the terpenes) from the water captured by your freeze dryer and use them to add value to your operation.

Once you’ve separated the terpenes from your freeze dryer drain water, there are two ways you can use them to add value. (1) You can add the recaptured terpenes to your rosin carts to reduce the viscosity of the rosin or (2) you can sell the terpenes as-is for a premium. The result for you as a grower or processor is added value and better margin capture with minimal additional effort.

The Freeze Dryer Terpene Extraction Process Step by Step

To capture a decent amount of terpenes from your freeze dryer, collect the freeze drying drain water after drying a terpene-rich substance like live bubble hash rather than whole cannabis flower, as the terpene content is likely to be more concentrated in hash. It’s important to keep in mind, however, that you’ll generally get a similar range of terpenes no matter which starting material you choose—those that tend to become volatile and sublimate in the freeze drying process.

What You'll Need 

• A small vial
• A 1000 mL volumetric flask with a glass stopper
• A large mason jar
• 25µm rosin bags
• A small rubber band
• A large airtight jar
• A 10 mL glass pipette
• A food-grade funnel

Method

1. Once the Dry cycle has finished on your freeze dryer, select Defrost.
2. Place the large mason jar under the drain hose.
3. Open the drain valve.
4. Allow the Defrost cycle to fill the mason jar.
5. Pour the contents of the mason jar into the flask, making sure to fill into the neck of the flask.
6. Put the glass stopper on the flask.
7. Place the flask in the fridge for a few hours.
8. Remove the flask from the fridge when separation is visible. You should see a small amount of clear liquid floating on top of the white hydrosol. This contains the small amount of aromatic oils (terpenes) that were removed from your concentrate or flowers in the freeze dryer.
9. Remove the glass stopper from the flask and grab the pipette.
10. Use the pipette to pull off the top layer of clear liquid. It's ok if you suck up a small amount of the white hydrosol as well. 
11. Let the hydrosol sink to the bottom and push it out of the pipette until only clear liquid remains.
12. Deposit the clear liquid into the airtight jar.
13. Place the airtight jar in the freezer for a few hours.
14. After a few hours, the water will freeze and the terpenes will float. You should see a layer of ice at the bottom of the jar.
15. Pour the floating liquid into the 25-micron bag to filter out any remaining hydrosol, using the rubber band to secure the 25-micron bag to the pipette.
16. Deposit your terpenes into a small vial.
17. You now have solventless terpenes!

Extracting terpenes from the freeze dryer might seem like a bit of a long process, but you'll soon get the hang of it. We've produced a video explaining how to capture solventless terpenes from your freeze dryer that shows each step being performed.

Why Terpenes Are Separated for Use in Cannabis Extracts

There are three primary motivations for terpene separation and their addition to either solvent-based or solventless extracts:

1. Terpenes are often added to solvent-based extracts at the end of the hydrocarbon extraction and purging process, as some of the terpenes are removed when the residual solvents are collected and the extract is purged under a vacuum. 
2. Cannabis-derived terpenes (or terpenes extracted from other plants) are typically added to vape carts made with distillates, as distillates have no measurable terpene content.
3. In solventless extraction, terpenes can be added to rosin to achieve the desired viscosity and flavor for cartridges. We have another video that covers the process of adding terpenes from the freeze dryer to rosin for carts.

Can You Isolate Specific Terpenes?

There is a popular theory that individual terpenes can be separated by heating terp oil to specific temperatures, or that you can isolate a specific flavor by heating a vape pen to a certain temperature. In reality, cannabis terpenes become volatile and vaporize at a range of temperatures, depending on the amount of time at which the oil is held at a certain temperature. 

Using this chart from Fragrantica.com, we can see that citrus and herbal terpenes (which are more volatile) represent the "top notes'' in any oil, with floral, spicy, and fruity fragrances in the middle (''heart notes"), and nutty, woody flavors as the "base notes." When you vape cannabis oil—either solvent-based or solventless—the most volatile terpenes (the top notes) will vaporize more quickly and the base notes will vaporize more slowly. At higher temperatures, the entire blend will vaporize more quickly and you'll notice the base notes sooner than you would at lower temperatures.

In the supplementary freeze dryer terpene recapture process, we keep the entire mixture cold to prevent any of the terpenes that came through in the drain water from vaporizing or degrading during separation. After you’ve separated the terpenes, the oil should be kept in the fridge or freezer. If you later mix the terpenes with decarbed rosin to make carts, you won’t heat the mixture any higher than 140 °F (although that's a topic for another day).

The Essence of Cannabis at Your Fingertips

As you can see, capturing and isolating additional terpenes from the hash freeze drying process is easy if you use a freeze dryer as part of your workflow. With cold temperatures and time, the oils will naturally rise to the top of the hydrosol for collection and filtering.

Once you've separated the terpenes, be sure to keep them in an airtight container in the freezer to prevent terpene degradation. You will then have an aromatic oil that you can add to rosin carts or sell to solvent extraction facilities and consumers. Bon appetit!