By Robert Pardee

Everything decays. In cannabis, this eventuality causes the enzyme THCa (the non-psycoactive tetrahydrocannabinolic acid) to oxidize and chemically transform in a short period of time, rendering lab THCa potency tests moot. As THCa is being poked and prodded by scientists seeking new medical discoveries, even under the ugly umbrella of a Schedule I drug, today’s cannabis farmer must press pause on decay by slowing down oxidation to preserve the valuable cannabinoid.

Oxidized cannabis will lead to mislabeled products on retail shelves, which can pose a significant problem for consumers. For example, imagine someone seeking the neuroprotective antioxidants that high-yielding THC provides, but instead, receives a dose of CBN–the result of oxidized THCa. The consumer will still get high because CBN is psychoactive, but will not receive the THCa efficacy as printed on that label.

Oxidation is the chemical reaction of an atom or compound, losing one or more electrons. This electron loss leads to hydrogen loss. THCa has 30 hydrogen atoms. When it loses four from oxidizing, it becomes CBNa; a psychoactive sedative when activated. That’s all it takes–just four hydrogen atoms!

There are three major contributors to cannabinoid decomposition: oxygen, UV light and heat. Oxygen (O2) is 21 percent of our livable atmosphere. It also poses the biggest threat to the cannabis preservation process. The invisible gas is always present and, unless removed, will cause not only the loss of THCa, but also a reduction in flavor and color after the cure process.

Exposure to oxygen also encourages aerobic bacteria and other complex organisms to thrive. Their interactions in the air and on the surface of the cannabis flower transform once marketable, aromatic terpenes into the rancid smell of wet hay.

Ultraviolet light (UV light) deteriorates cannabinoids through photo-degradation. The exposure of harvested cannabis to either sunlight or artificial light can lead to rapid photo-degradation of trichomes, caused by absorption of photons. When the photon is absorbed, it transfers energy to the electron and causes unstable molecules to eventually oxidize or hydrolyze. Pigments, proteins, and fats found in cannabis become discolored, have an off-flavor, and accelerate the conversion of THCa to CBNa. 

In addition, UV light generated from Light Emitting Diodes (LEDs) can negatively impact enzymes from performing their duty of converting THCa to THC. As many researchers know, THCa is an enzyme found inside the plant and is responsible for the chemical reaction creating the euphoric feelings of THC. Most enzymes are highly sensitive to UV light in all of its ranges, and their important functions can irreversibly drop even after a short exposure to LEDs.

Lastly, a rise in temperature increases the rate of oxidation. Harvested cannabis exposed to temperatures of 70 degrees Fahrenheit will speed up oxidation because molecules are colliding more often. These microscopic collisions increase the opportunity to create oxidized cannabis. Heat, which can be generated by light, also increases moisture loss, resulting in a brittle, overly dry flower.

Solutions 

Poorly stored cannabis greatly diminishes the shelf life of THCa. Although growers may get better at growing superior cannabinoids every harvest, many are not improving their packaging, storing, or transport methods to protect their cannabinoids from oxidation. Here are some simple recommendations to consider that will help keep your terpenes fresh this harvest: 

Trimmed to order

Keep dried, bucked, and cured flower away from the trimmer until the last possible moment. Trimming is violent and destroys trichomes. Trichomes are the sparkly crystals that manufacture the highest concentration of cannabinoids on the plant. By trimming cannabis too soon before it’s sold, a cultivator loses the immediate terpene profile and expedites oxidation of THCa. 

Remove oxygen from your container post-cure

O2 is required in the curing process. Slow down post-cure oxidation by removing air from glass jars or cans via 100-percent vacuum. However, copolymers and biopolymers (plastics) collapse when vacuumed and require a machine to replace the atmosphere with an inert gas, without crushing the valuable trichomes in the process. By displacing the oxygen and replacing it with an inert gas, O2 is removed and the trichome isn’t bruised (nearly 80 percent of perishable commodities in the grocery store are packaged this way–cannabis will be next).

Oxidation will also occur in the freezer. O2 should be removed and replaced with inert gas when packaging “fresh-frozen.”

Store in Low-Permeable Containers 

Permeability is the state, or quality, of a material or membrane that causes it to allow air to pass through it. Glass and tin have low permeable walls that slow down air from naturally coming and going, but may not be economically viable for a larger operation. Plastic, when used in combination with high-barrier films, provides low-permeable transition rates equal to that of glass, slowing down oxidation.

Not all plastics are the same. Ask your plastic salesperson for a Material Safety Data Sheet (MSDS). If they can’t provide one, then don’t use their products. Licensed farms should keep packaging MSDS on the property for compliance.

Plastics that lack high-barrier properties invite air in through microscopic pores at fast rates, speeding up oxidation and should be avoided.

Keep everything in the dark, with temperatures ranging between 50 to 65 degrees Fahrenheit. Photochemical reactions can be minimized by keeping harvested cannabis away from natural and artificial light at all times during post-production, only using it briefly when inspecting, bucking, trimming, or packaging. Keep cannabis stored in the dark and not under LED lights (even less than ten nanometer outputs will cause enzymes to misbehave). If you use a transparent container like glass or plastic, keep it stored in a lightproof container and bring it out only to show the buyer. Dispensaries will reduce oxidation by protecting all their cannabis products from the light, bringing out only samples.

No matter how it’s grown, THCa is a valuable, volatile cannabinoid that has the opportunity to improve a person’s life, and should, at all costs, be protected from oxidizing.  

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