Terpenes & Drying: Separating Fact from Fiction, Not Terps from Flower.

1Terpenes, otherwise known affectionately in the cannabis culture lexicon as “terps,” are the aromatic compounds found in all plants that give the plant its unique flavor and smell profile. From the limonene in lemons to the linalool in lavender, terpenes are how we identify a plant by its aroma. Cannabis phenotypes and strains have some of the most unique terpene profile combinations of any plant family on the planet. Terpenes are found in the trichomes of flowers. They can be broken down into two categories or types: monoterpenes (i.e., Myrcene, Pinene, Limonene, etc.) and sesquiterpenes  (i.e., Caryophyllene, Humulene, Germacrene, etc.). 2There is strong scientific evidence that (in general) terpenes may have a direct physiological effect on the body due to their small molecular size passing through the blood-brain barrier.

For this reason, the loss of terpenes during the growing, drying, and curing process is a massive area of interest to cultivators, dispensary owners, and scientific researchers alike. What research is out there regarding terpene degradation in the drying process? How can the drying and curing process be optimized and automated without destroying these valuable cannabis derivatives? Are there automated methods (freeze-drying, convective closed-loop systems, etc.) that are better than others at preserving the terpene content of cannabis flowers?

3In general, under typical “low and slow” conditions that have been standard in the industry for decades, there is an almost 75% loss of overall flower weight during the first three days of drying. With it, a good portion of terpene content as well. Terpene loss begins to plateau over the remaining 4-7 drying time average until the flower reaches the ideal 10%-14% moisture level that most cultivators want their flower to get to for the product to be suitable as a smokable flower for dispensary shelves.

Not all terpenes, though, are affected the same during the drying process. Monoterpenes and sesquiterpenes behave inversely during the drying process. 4One study showed that as drying & curing time increased, monoterpenes would lose overall content while sesquiterpenes would increase in content. After one week of drying at room temperature (68F-72F), monoterpenes decreased by almost 55%, while sesquiterpenes nearly doubled during that same period. This equated to a net overall terpene loss of roughly 31% (mono and sesquiterpenes net balance) after one week of drying under standard room temp and standard 55%-65% relative humidity. After one week of drying and one month of curing/storage, that turned into a 44.8% net loss. After one week of drying and three months of curing/storage, terpene net loss was almost 55.2%, with a significant conversion from monoterpenes to sesquiterpenes. The general conclusion from the study is that there is a point of intersection between monoterpene degradation and sesquiterpene enhancement during the drying process, where both are maximized, and overall terpene loss is further mitigated. The question then is, if cannabis flower loses that much terpene content during the standard “low and slow” process that the industry knows and loves – how can any of the automated drying & curing methods currently on the market perform better? Is all the hype about freeze-drying warranted, or are the more traditional convective automated methods (which mimic the industry standard)?

An academic study at Dalhousie University in Halifax set out to determine just that by examining how varying drying temperatures and relative humidity points would affect terpene content and overall quality during the drying process. This compared fresh cannabis flower against freeze-drying as well as against standard convective drying at varying temperature settings. 5The study found that total terpene content readings between 20C-30C (68F-86F) were greater (0.34 %/weight – 0.38 %/weight) than freeze-drying, which produced consistent total terpene levels around 0.30% by weight. This study’s conclusion perhaps highlights why the industry is so adamant about sticking to the standard “low and slow” drying methods.

For this reason, we here at Cann Drying Systems are not attempting to “reinvent the wheel” but rather automate that “wheel” to help bring process efficiency to this crucial part of the post-harvest process. Our closed-loop convective systems are also designed to capture the vapor coming off your crop in our closed-loop chamber by condensing that vapor back into terpene-rich water that can then be separated. This allows our customers to get back a large portion of those (otherwise lost) valuable terpenes that will be lost, whether they are hang drying in an old school dry room or using a more modern automated system.

You may be wondering at this point – exactly how much of these lost terpenes are Cann’s systems able to recapture? We are conducting several academic and commercial studies with our customers to determine precisely how much. We look forward to sharing this information with you in a future case study white paper that will be published in 2022.


1 https://www.merriam-webster.com/dictionary/terpene
2 Cho KS, Lim YR, Lee K, Lee J, Lee JH, Lee IS. Terpenes from Forests and Human Health. Toxicol Res. 2017;33(2):97-106. doi:10.5487/TR.2017.33.2.097
3 https://savetheterps.org/terps/
4 Ross, S.A., & Elsohly, M.A. (1996). The volatile oil composition of fresh and air-dried buds of Cannabis sativa. Journal of natural products, 59 1, 49-51
5 Challa, S. K. R. (2020, March). DRYING KINETICS AND THE EFFECTS OF DRYING METHODS ON QUALITY (CBD, TERPENES AND COLOR) OF HEMP (Cannabis sativa L.) BUDS. Https://Dalspace.Library.Dal.ca/Bitstream/Handle/10222/80480/Challa-Saikiran-MSc-Agri-March-2020.Pdf?Sequence=1&isAllowed=y. Retrieved September 11, 2021, from https://dalspace.library.dal.ca/bitstream/handle/10222/80480/Challa-Saikiran-MSc-Agri-March-2020.pdf?sequence=1&isAllowed=y