Terpenes are a group of naturally occurring volatile compounds that are produced by animals and plants alike. While terpenes may be a topic you may be unfamiliar with–surprise!–they are all around you. These compounds are the relaxing aroma of lavender, the breath of fresh air from a pine forest, and the smell of freshly cut grass; moreover, they are what make certain plants have a distinctive smell. In chemistry, most terpenes are classified as aromatics because of their ring-like structure. As it hints, aromatics give off an “aroma” that is easily picked up by one’s senses.
Brief Overview of Characteristics
Terpenes are composed of structures called isoprenes, which have a molecular formula of (C5H8). The simplest class of terpene, monoterpenes, consists of two of these isoprene structures bonded together. An example of this would be the citrus-scented limonene, which consists of two of the isoprene structures combined together. Add another isoprene unit and you will have a sesquiterpene; another isoprene and it’s a diterpene- growing in molecular weight with every isoprene unit added. In other words, terpenes are classified by the number of isoprene units and will distinguish the physical characteristics of the compound (e.g boiling point, color, and smell). Simpler terpenes will have a higher tendency to evaporate due to its lower boiling point given that they have fewer bonds; therefore, less energy is required to change the compound into its gaseous phase. Monoterpenes (e.g limonene, myrcene) evaporate first and will be the high-notes given off your flower. More complex terpenes will linger the longest and will be your base-notes, often being your muskier terpenes; however, they exist in smaller quantities.
Use in Hemp
Look at your flower and you will see a crystalline-frost covering the surface of your leaves and buds. Run your fingers over these crystals and you'll notice it's a fairly sticky substance and smells very much what you’d expect your strain to smell like. These structures are the trichomes of the plant that serve as the secretory glands responsible for the production of a resin containing cannabinoids and terpenes alike. These nano-sized structures consist of a stalk supporting a mushroom-bulbous head, which contains the valued resin. The yield of trichomes is highly-dependent on the plant’s environmental factors such as nutrient-uptake, water-uptake, temperature, humidity, airflow, and light-spectrum. Improving such environmental conditions would increase the production of trichomes, thus increasing the yield of valuable terpenes and cannabinoids.
In nature, flowering hemp begins to produce trichomes to serve as a defense mechanism aimed at deterring invading pests and animals. The bitter taste of the terpenes which the trichomes produce make the plant unpalatable to organisms seeking to make a meal out of the plant. It’s not only large predators that terpenes deter; the aromatic resin holds strong antibacterial qualities that protect the hemp's foliage from harmful bacteria and fungi. On the flip side, the terpenes also aid in attracting friendly-pollinators that ecologically aid in the increase of the plant’s population size.
The Important Function of Terpenes
Over 100 terpene compounds have been identified and known to be produced in the trichomes of the plant. However, not all terpenes are produced equally in hemp and the aroma-profile is highly dependent on the strain of the flower. Durban Poison, a Sativa deriving from African ancestry, emits a fruity and herbal aroma-profile. Terpinolene, Myrcene, and Ocimene are the most common terpenes found within Durban Poison; those responsible for giving the strain its off-the-bat sweet, fruity, earthy aroma. Dozens of other terpenes are present within the strain, but often their quantities are too minuscule to be deemed significant in its aromatic-profile. However, the presence of even the most minor terpenes contributes a part in building a novel scent, even if alone they impose the most subtle aroma.
In addition to producing the strain’s scent, research has shown that terpenes may take part in inducing the “entourage effect”- the collective medicinal properties created by cannabinoids and terpenes performing in a synergistic (combined) relationship. Whether it's smoked or vaped, the inhaled hemp compounds enter the bloodstream where it interacts with the endocannabinoid system (ECS). This cell signaling system, with the aid of receptors and enzymes, regulates your body's homeostasis- the body's ability to maintain a relatively constant and healthy environment. Cannabinoids may regulate overshooting brain neurons that could be affecting mood, sleep, and pain to name a few. In addition, cannabinoids may aid in introducing supporting immune cells to fend-off harmful bacteria across the body. Terpenes, with their own medicinal qualities (e.g anti-inflammatory, distressing, appetite-inducing, alertness), simultaneously bind to the cell receptor with cannabinoids. Therefore, cannabinoids and terpenes may impose their medicinal qualities jointly and create an entourage effect that is uniquely determined by strain’s concoction of these two classes of compounds. There is much research still yet needed to properly understand the individual medicinal effects of cannabinoids and terpenes alike; until then, we cannot understand the collective “entourage effect” hemp may provide.
Terpenes in The Industry
The terpenes are valued for two reasons; these compounds provide an aromatic profile in your bud and research shows that terpenes may aid in increasing the medicinal benefits of consuming hemp. In the industry, hemp has expanded into a wide range of consumable products in the forms of various concentrates (e.g distillate, wax, budder, sauce, shatter). Depending on the concentrate, the terpene content of the product may vary significantly than what would have been found before extraction. Exposure to heat, even at room temperature, in conjunction with atmospheric gas may lead to a rapid loss/oxidation of terpene content.
Activities like curing, extraction, solvent reclamation, and filtration can all progress the loss of terpenes; therefore, it’s advised to minimize the amount of processing if one wishes to retain a greater concentration of terpenes in the end-product. Long exposure to heat in short-path distillation, for example, renders an oil almost desolate of terpenes and the identity of its strain is no longer recognizable. Terpenes are volatile compounds that on average evaporate at temperatures <150C/302F (under vacuum); therefore, the fraction of terpenes is boiled off almost completely before cannabinoids are distilled (>150C/302F).
“So I collected my terpenes in my ‘heads’ (first fraction in distillation), can I add it back?” More than likely the answer is no. Not only have your terpenes been degraded into an undesired compound, but that collection flask could be contaminated with impurities such as a residual solvent. If you want to produce a product with a terpene profile, whether it’s to enhance your shatter or rejuvenate your distillate, it may be beneficial to introduce an external source of extracted terpenes.
Further Use of Terpenes
Typically these terpenes are extracted using steam distillation, suspending a basket of plant material over boiling water and allowing for the compounds to be carried over via steam into a collection flask. However, the heat will lead to some loss of these highly-volatile terpenes. This can be an issue if you’re seeking to retain the true integrity and medicinal value of a strain. Some hemp-derived terpenes exist within the plant in small concentrations and losing even the smallest amount could be significant. In addition, consistency in the profile of the terpenes may vary if the genetics of the strain were not standardized in processing.
Given two plants from two different growers, their profiles may vary since many “true” strains have been lost after generations of cross-breeding and there are little moderators tracking genetics. From a cost-effective standpoint, hemp-derived terpenes are generally more costly due to the price of the plant material. Often, processors incorporate botanical-derived terpenes if the cost is a limiting factor.
Limonene from hemp will be the same limonene found in cheaper material such as citrus fruit; both terpenes will have the same therapeutic effects. Theoretically, one could analyze the terpene content of a particular strain and mimic that in a blend. The tricky part would be hitting those minor terpenes that exist in very small quantities in the original strain. With the hundreds of terpenes found in hemp, many unknown, this can turn into a tedious process. There are pros and cons to whether you choose to incorporate hemp-derived terpenes or botanical.
Whether it's being able to analytically mark terpenes in strains, increase accuracy in extraction, or being able to preserve a higher terpene content in concentrates; the field of hemp is ever growing in a time of legality. With the limited amount of technology we have at hand, it may be difficult to reach that perfect ratio of terpenes and your strain profile may not be perfect. Maybe you’re not aiming at mimicking a strain? Have fun and make your own in-house blend! Trial and error are embedded in this novel and exciting field.
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