Not All Terpenes Are Created Equal

There continues to be a proliferation of overdried cannabis in legal markets caused by factors ranging from poor drying and curing environments and/or practices to purposeful rapid overdrying to minimize bacterial or fungal contamination risk.

When adding these practices to an already flooded market with a slow retail turnover rate, the result is a backlog where freshly harvested cannabis sits in warehouses while older and older harvests get shipped out. And as dried cannabis ages, it inevitably diminishes in quality as terpenes degrade and evaporate.

As a rule of thumb, I consider dried raw cannabis buds to be a perishable item with a shelf life of approximately one year if stored in a cool, dark environment. This can be extended if the sealed containers are stored in a sub-zero freezer until ready for delivery to the point of sale. I have certainly seen incredible cannabis that was over a year old, but it had been properly stored and cared for.

Terpene Frenzy

With the increase of older and/or overdried cannabis, there has been a steady rise in both non-cannabis-derived and cannabis-derived terpenes in multiple forms being produced and distributed to cannabis and hemp growers.

The proliferation of terpene additives is accompanied by gizmos and gadgets designed to facilitate their application to terpene-devoid cannabis buds. These applicators range from plastic sprayers to pressurized chambers designed to deeply infuse the terpenes into the plant material.

It is fairly well-known (and often mentioned on packaging and in marketing materials) that many vape products utilize added terpenes. But their usage is spreading beyond concentrates. I asked one of the largest steam-distilled, cannabis-derived terpene producers who its largest customer was: It was one of the largest greenhouse growers in the state, who infused the terpenes into the cannabis destined for its pre-rolled joints.

Despite the efforts, I am of the opinion that you can't fix broken, and terpene-devoid cannabis is broken. Why would someone overdry and evaporate existing terpenes, to in turn reapply alternative terpenes? Sounds like a pointless exercise, as terpenes are compounds that work together with a multitude of cannabinoids. It’s this combination that is responsible for the entourage/synergistic effects with the human endocannabinoid system.

Not All Terpenes Are Created Equal

Terpenes are natural aromatic compounds that are responsible for both the aroma and flavor characteristics in cannabis, other plants, animals, beers, and everything in between. As of 2017, more than 560 unique chemical constituents have been identified in cannabis, with more than 100 unique cannabinoids and more than 150 individual terpenes noted.

So, where are terpenes available for use on cannabis sourced from today?

1. Food-grade terpenes: Typically derived from plants and fruits through steam distillation or hydro-distillation. Steam-distilled cannabis-derived terpenes are available for sale but will often lack the vibrancy of the oils collected that were not subjected to heat.
2. CO₂-extracted fractionalized terpenes: CO₂-derived cannabis terpenes pale in comparison to other extraction methods. CO₂ extractors often utilize dried cannabis as their input material, which has minimal terpene content to start with.
3. Thin-film distilled cannabis-derived terpenes: This process utilizes heat, which degrades and converts terpenes.
4. Rosin sauce: Rosin is melted, and cannabinoids and terpenes are separated under vacuum. These terpenes are utilized in rosin vape cartridges.
5. Cannabis-derived hydrocarbon extract: This process yields a sauce separating THCA from the remaining cannabinoids and terpenes. These terpenes are also predominantly utilized in vape carts and sometimes added to flavorless distillates for use in vape carts.

Each of these terpene types contains essential oils to varying degrees.

The term essential oil is a contraction of the original “quintessential oil” derived from the Aristotelian concept that matter is composed of four elements, specifically air, fire, water, and earth. The fifth element, or quintessence, was considered to be the “spirit” or “life force.” Distillation and evaporation were thought to be the processes of removing the spirit or life force from the plant. This is also reflected in modern language when we use the term “spirits” to describe alcoholic beverages.

This analogy may be more fact than metaphor, as headspace measurement technology makes it possible to detect the volatile components of the plant's “aura.”

Aromatic Complexities

Fresh bud oil is comprised mainly of monoterpenes (92%) with 7% sesquiterpenes and approximately 1% other chemical classes such as simple ketones, esters, and thiols. Not unexpectedly, drying the plant material resulted in an overall reduction in the percentage of the oil recovered. Most of the loss appears to take place during the first week of drying. Drying results in a significantly greater loss of monoterpenes than of sesquiterpenes.

As of yet, it has been nearly impossible to recreate the aromatic potential of the more than 150 known cannabis terpenes using just a few food-grade terpenes. They are predominantly sold as single terpene compositions—pinene, limonene, linalool, etc.

The steam distillation process alone destroys and converts the original terpene composition from the original plant material, meaning these single terpene compositions are not even a true representation of their source. The most aromatic extractions occur at or below ambient temperatures, which prevents thermal degradation.

Even cannabis-derived terpenes have their limitations. CO₂ extraction utilizes dried plant material, where a percentage of terpenes is already lost during drying. Another portion is then lost during CO₂ recovery.

The resulting extract from steam or hydro-distillation is compromised by heat, and a percentage of water-soluble terpenes is lost to the water.

Thin-film distillation also leverages heat, compromising the resulting extract. Additionally, the initial extraction process might isolate only a fraction of the terpenes present in the fresh bud.

Priority Check

Rather than reinfusing a lesser quality essential oil/terpene, which will ultimately result in poor-quality final products, perhaps the efforts could be better spent properly drying and curing the buds with emphasis on terpene preservation and retention. This includes better protocols and infrastructure for long-term storage, as it is likely to take years for stored inventories to normalize.

This way, we might see more cannabis products with well-preserved souls and auras, which would be a refreshing change of pace.