Very recent thoughts on storage from my dispensary:
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"THCA and THC Marijuana contains a group of compounds called cannabinoids. These cannabinoids are formed by the plant in their acidic form, e.g. THCA. THCA has historically been described as not being bioavailable, meaning that you can't absorb it in its acidic form. Exposure to room temperatures over time will cause acidic cannabinoids to slowly decarboxylate to a pH neutral form, e.g. THC. Exposure to higher heat can immediately decarboxylate THCA into THC. The thinking is that smoking, vaporizing or cooking cannabis provides enough heat to decarboxylate the THCA into an active form. Which appears to be true, except... Dr. Arno Hazekamp, a very bright young scientist from Holland, studied cannabis tea with a liquid chromatography machine. Cannabis tea is interesting because the hot water really shouldn't be an efficient method for decarboxylating THCA to THC, unless you boiled the raw cannabis for a couple of hours. And Hazekamp proved that, yet he also found that despite the high levels of THCA in cannabis tea, it appears to be pretty good at delivering an strong medicinal effect. This effect noted by Hazekamp is causing some reevaluation of the bioavailability and effects of THCA. The other thing that Hazekamp found was that the THC(A) in cannabis tea precipitates onto the walls of the container unless you add an emulsifier. The best emulsifier he found was nondairy creamer. It might be disgusting, but it works much better than milk or cream to keep the THC(A) in solution.
Where exactly is the THC(A) in marijuana? Almost exclusively in heads of the trichome hairs. The trichome heads are pretty fragile, so it's typical for them to rupture during trimming, storage or handling. Trichomes are often harvested from the plant as kif or extracted using cold water or solvents. Using liquid chromatography, you can gauge how well the trichomes have been treated by the examining the ratio of THCA to THC to CBN... The more THCA, the better its been handled and stored.
Should I freeze my cannabis to store it? Sure, with a few caveats... First, residual water in raw cannabis will freeze, expand, and rupture the cell walls of the cannabis. It will also make the trichomes and their glandular heads brittle. So, you want to handle frozen cannabis very carefully. Only pull out what you're going to use. Don't freeze, thaw, then refreeze. Only freeze well-cured cannabis (9% water weight, which means pretty crisp yet still very aromatic) cannabis."
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The following was added a bit later and may be a bit of concern for those that dry their herb before using them in their vapes.......
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"When dried flowers start to lose additional moisture, it can lead to deterioration of cannabinoid content, but it's still only about 7% a month. Not great, but not terrible.
When dried cannabis loses too much residual water content, the rate at which its essential oils begin to evaporate appears to accelerate. If you're using a Foodsaver, you should be stabilizing the rate of water loss. The key for your setup will be minimizing exposure to heat and light. I would divide up your stash into smaller portions and bag these portions with the Foodsaver. We've found that dried cannabis can lose a lot of water very quickly when its package is opened in a dry room, so minimize this by reducing your "portion" size. The only warning is to make certain that you're not pulling so much oxygen out with your Foodsaver that you inadvertently provide anaerobic bacteria with a chance to gain a foothold. Moist bud and low oxygen is a recipe for disaster."