By: Ryan Pardee

Protecting THCa from Oxidation

Published in Grow Magazine Harvest Issue 2018.

Everything decays. This eventuality causes the enzyme THCa (or THC when activated) 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 1 Drug, today’s cannabis farmer must press pause on decay to slow down oxidation to preserve valuable cannabinoids.

Oxidized cannabis will lead to mislabeled products on retail shelves; which can pose a significant problem for consumers. For example, imagen someone seeking the neuroprotective antioxidants that high-yielding THC provides but, instead, receive 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 4 from oxidizing, it becomes CBNa; a psychoactive sedative when activated. That’s all it takes! 4 hydrogen atoms. 

There are three major contributors to oxidized cannabis: Oxygen, UV-Light and Heat. 

Oxygen (O2) is 21% of our livable atmosphere and greatly contributes to oxidized cannabis. The invisible gas is always present and unless removed, after the cure process, will cause not only the loss in THCa, but also a reduction in flavor and color.

O2 exposure also encourages aerobic bacteria and other complex organisms to live. 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. 

Second is Ultra-Violet Light (UV-Light). UV-Light increases oxidation through photo-degradation. The exposure of harvested cannabis to either sun-light or artificial-light, can lead to rapid photodegradation of the trichome. Photodegradation is the alteration of materials by light 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. The end results are 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 preforming their duty of converting THCa to THC. As many researches know, THCa is an enzyme found inside the plant and is responsible for the chemical reaction creating the euphoria 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 time exposure to LEDs. 

Lastly, the rise in temperature increases the rate of oxidation. Harvested cannabis exposed to temperatures at 70°F 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.  


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

Trim when the order gets in

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 its 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% 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% of perishable commodities in the grocery store are packaged this way- cannabis will be next). 

Also, oxidizing will 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. Plastic, when used in combination with high-barrier films, provide equally low permeable transition rates to glass that slow down oxidation.  

Not all plastics are the same. Ask your plastic salesperson for a Material Safety Data Sheet. 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 through microscopic pores at fast rates, speeding up oxidation, and should be avoided. 

Keep everything in the dark, with temperatures ranging between 50-65 degrees;

Photochemical reactions can be minimized by keeping harvested cannabis away from natural and artificial light at 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 10 nanometer outputs will cause enzymes to misbehave). If you use a transparent container like glass or plastic, keep it stored in a light-proof container and bring it out only to show 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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