Chemistry of Decarboxylation
Explore the science behind stronger edibles
Decarboxylation isn’t just for edibles, it is also a vital process that occurs in all animal life! If you breathe out carbon dioxide, you are decarboxylating inside your body.
“Essentially, all the carbon dioxide evolved in fermentation and respiration is produced by decarboxylation of organic acids.”
~Nobel Prize-winning biochemist Severo Ochoa
When it comes to edibles, decarboxylation (decarbing) unlocks the psychoactive chemicals of the plant that are locked away in a non-psychoactive organic acid. Unfortunately, your body is unable to decarboxylate the acids in fresh bud on its own. Fortunately, decarbing outside your body is a simple process, requiring only a bit of heat to turn the acid in your herb into euphoria-inducing ☕HC.
Who discovered decarboxylation?
Though it is unknown who first discovered decarboxylation, one of the first written mentions of heating herb is in a recipe from the Egyptian Fayyum Medical Book from the 2nd century C.E.. Since it doesn’t specify how much heat to use, it’s unclear if it is referring to decarbing. Another early example that more clearly refers to decarbing and edibles is a traditional Chinese medicine recipe for pain relief from 1070 C.E. which calls for stir-frying seeds then infusing them in alcohol and taking on an empty stomach.
The chemistry of decarbing didn’t get a full scientific description until the 20th century. One of the founders of modern biochemistry, Carl Neuberg, was the first to identify it in 1911 when he found the enzyme responsible for catalyzing the decarboxylation of pyruvic acid. Further research revealed that it is a vital step in the metabolism of sugar between glycolysis and the Krebs cycle which generates energy in mitochondria. But Neuberg never applied this insight to recreational use of herb.
People didn’t really understand exactly what was going on during decarboxylation in herb until its psychoactive chemicals were identified in the 1960’s. In 1964, Δ9-tetrahydrocannabinol l was first isolated. In 1965, its minimally psychoactive precursor organic acid was first discovered, revealing the importance of decarbing edibles . Though the importance of decarbing was then understood, it wasn’t until 1968 that the popularity of edibles and decarbing spread widely in the USA after magic brownies were prominently featured in the cult hit movie I Love You, Alice B. Toklas.
The chemistry of decarboxylation
Decarboxylation converts an acid into a psychoactive form. CO₂ is a byproduct.
Decarboxylation means removing carboxylic acid by removing CO₂ from a compound. In most practical cases, this process is sped up by applying heat, though it can happen spontaneously at room temperature over very long periods of time (i.e. months to years).
For herb, decarboxylation is a two-step process. First, hydrogen bonds break in the precursor compound, forming a beta keto acid. Then the acid rebonds those hydrogens and releases the CO₂, breaking the bond with heat.
Graph A shows how the concentration of acid changes with different temperatures during decarboxylation. Graph B shows the increase of ☕HC during decarboxylation.
Side effects of decarboxylation
~ Ethan B Russo, board-certified neurologist and psychopharmacology researcher
Decarboxylation is a simple process compared to other reactions caused by heating your herb. Because herb contains hundreds of different chemicals, when you apply heat to flowers, buds and trichomes, you’re affecting many of these other compounds as well. Pure decarboxylation only happens if you work with an extract like shatter. If you’re deoxycarbolating plant material, there will be secondary chemical changes caused by the heat.
Side effects using heat to decarboxylate fresh herb include:
- denaturing of terpenes
- evaporation of water and oil
- Maillard reactions
- mass loss
Some of these changes are actually perks. By removing extra water, you will decrease the likelihood of mold growing on your stash and it’ll last longer.
Some of the other changes are less desirable. Heat can damage terpenes which are the naturally-occurring chemicals that generate herbal, citrusy, spicy flavors and may have health benefits. Terpenes can also be desirable because they can affect the quality of your high via the entourage effect. If preserving terpenes is important to you, decarb at the lowest temperature possible or consider trying the no-heat method, but keep in mind it may take months to years to complete the process.
Oxidation during decarboxylation
The psychoactive compounds in herb are volatile and will continue to break down even during the decarboxylation process. This secondary process of oxidation will make your finished product less potent and will increase the amount of chemicals in your herb that have a sedative effect.
Complete decarbing can happen as low as 60°C and at higher than 130°C but will generally result in more oxidation. If herb is exposed to oxygen and light during the decarboxylation process, oxidation speeds up. To avoid oxidation and get the most efficient results, minimize exposure to light and air while decarbing and target the ideal temperature range between 110 and 130° C. For more tips on how to optimize efficiency, check out our advanced decarbing techniques .
After decarbing using heat, you may notice your bud has turned light brown and has new toasty aromas and flavors. This change is the result of heat-induced Maillard reactions which convert the structure of the proteins and sugars in your plant material into new flavorful compounds. The process is the same as the process found when you toast bread.
If you want to reduce these sometimes unwanted flavors, you can combat them by using a water cure. To water cure, simply soak your bud in water in a mason jar, changing the water every day for five days, then strain out your bud and let it dry on drying racks for another couple of days. This will remove most of the sugars that cause Maillard reactions as well as many of the other strong flavor components from terpenes.
Mass loss from decarboxylation
If you were to have a perfect conversion with no loss to oxidation while decarbing, you will still end up losing some mass. That’s because when decarboxylation happens, you lose CO₂ from the acid molecule.
This change will be hard to detect on the scale if you weigh your bud both before and after decarbing because the change will be in milligrams and you will also lose a greater weight of water at the same time.
This change will be noticeable however if you test the amount of organic acid and ☕HC in your bud before and after decarbing. How much mass loss can you expect from this chemical process? If you achieve perfect decarboxylation, you can expect to create an amount of active ingredient that is 88.7% the mass of the precursor organic acid.