Horticulture

Optimal Storage Conditions for Cannabis Flowers and Extracts

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Written by Sabina Pulone

The therapeutic potential of cannabis is attributed to cannabinoids and terpenoids: acting synergistically and present in different concentrations in each variety, these secondary metabolites are capable of exerting beneficial effects against inflammation, cancer, pain, neurological alterations, gastroenteric diseases, etc. [1]

The phytochemical composition of cannabis is linked to growing conditions and harvest period, but depending on storage conditions, variation in cannabinoid and terpene profiles is evident both in flowers and extracts. Terpenoids and cannabinoids are subject to change over time and may undergo oxidation, decarboxylation, isomerization, photochemical reactions, evaporation, and other degradation reactions. The standardization of therapeutically stable cannabis products is important to guarantee the consistency of medicinal effects on patients, and for this reason it is necessary to evaluate the optimal conditions to preserve the composition of naturally biosynthesized secondary metabolites. [1] The degradation rate of terpenoids has been reported to double for every 10 °C increase in temperature, but stability studies on these fragrant molecules are usually not directly related to cannabis [2].

Researchers are mainly focused on storage-dependent modifications of well-known phytocannabinoids and the degradation pathways of cannabis plants. Cannabinol (CBN) is the most widely used marker for determining cannabis aging: this cannabinoid can derive both from oxidation of Δ9-tetrahydrocannabinol (THC) and decarboxylation of cannabinolic acid (CBNA), which is the oxidation product of tetrahydrocannabinolic acid (THCA).

The recent scientific research of Milay et al. [1] reports data on the effect of grinding, solvent selection, storage time, and temperatures on phytocannabinoids and terpenoids. By analyzing cannabis inflorescences (both intact and ground samples) and cannabis extracts (dissolved in ethanol, dimethylsulfoxide [DMSO], or olive oil) stored in the dark at various temperatures (from 25 °C to -80 °C), Milay et al. [1] defined optimal postharvest storage conditions intended to limit secondary metabolite modification.

The storage temperature of 25 °C appeared as the most unfavourable to preserve phytocannabinoids over time (12 months), and the least modified profile was obtained in olive oil extracts; olive oil was noted for “conserving characteristics.” Decarboxylation was the main degradation route for phytocannabinoids.

Extraction significantly reduced starting terpene concentrations. The average terpenoid concentration (monoterpenes and sesquiterpenes) decreased in all samples and all storage conditions, with higher variations in ground samples and those stored at temperatures lower than -20 °C; the lowest temperature of -80 ºC resulted in the greatest losses. The best condition to maintain original phytocannabinoid and terpenoid composition during long storage periods, in both inflorescences and extracts, was at 4 °C.

These findings are relevant to cannabis manufacturers, growers, and distributors who must supply therapeutically stable cannabis products and limit adverse effects in comparison with the original material. [1]

 

References:

[1] Milay L, et al. Metabolic profiling of cannabis secondary metabolites for evaluation of optimal postharvest storage conditions. Frontiers in Plant Science. 2020. doi: 10.3389/fpls.2020.583605
[Journal Impact Factor = 4.407] [Times cited = 4 (Semantic Scholar)]

 

[2] Turek C, Florian CS. Stability of essential oils: A review. Comprehensive Reviews in Food Science and Food Safety. 2013;12(1):40–53. doi:10.1111/1541-4337.12006 [Journal Impact Factor = 12.811] [Times cited = 473 (Semantic Scholar)]

 

Image: Hemp crop_picture by Sabina Pulone

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Sabina Pulone

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