Water activity in cannabis drying standards and regulations
Each state sets its own regulations and testing requirements for dried cannabis, which can frequently change. Some states require water activity testing. Some do not. What doesn’t change from state to state are the water activity microbial growth limits. Whether or not specific states require water activity or mold testing, the quality of the dried cannabis product depends on the crop being consistently dried to a safe level.
To find out whether your state requires you to report water activity readings, how they can be taken and verified, and how they should be reported, consult your state marijuana board.
There are standards that relate either directly or indirectly to the testing of dried cannabis. These standards have been established by standards bodies, public or private organizations that have to establish, publish, and coordinate voluntary standards, guidelines that help clarify and control processes of importance to the public. As the cannabis industry develops, voluntary standards will help guide the development of regulations and can help give processors, wholesalers, manufacturers, dispensaries, retailers, and ultimately consumers the ability to compare and have confidence in the quality and safety of cannabis products. Using these standards is also a way for processors to differentiate their product in the marketplace.
Some of the most valuable of the standards are:
- ASTM D8196: Determination of Water Activity in Cannabis Flower, and
- ASTM D8197: Standard Specification for Maintaining Acceptable Water Activity Range (0.55 to 0.65) for Dry Cannabis Flower
The ASTM standards are the first to establish specific recommendations and ranges for measuring moisture in dried cannabis flower. ASTM D8196 lays out standard measurement procedures and guidelines. ASTM D8197 establishes the recommended range to address safety and quality issues.
USP Method 1112
The United States Pharmacopeia (USP) is an independent, not-for-profit, non-governmental body that sets quality, purity, strength, and identity standards for medicines, food ingredients, and dietary supplements. Many USP standards are enforceable by the FDA. Method <1112> provides “guidance in the influence of water activity as it pertains to product formulation susceptibility to microbial contamination.” The chapter includes a water activity limits microbial growth table, strategies for microbiological testing based on water activity, and methods for measuring water activity. USP <1112> is often used to justify reducing the amount of microbial limits testing needed for products with lower water activities.
This standard is issued by the Association of Official Analytical Chemists. Though it pertains officially to the determination of water activity in “canned vegetables,” section B on instruments and systems discusses acceptable methods for the determination of water activity and specifies acceptable sensors.
Compendium of Microbiology Water Activity Method Chapter 68
This chapter in the Compendium of Microbiology defines water activity, gives a brief review of measurement methods, discusses calibration and sample preparation, and includes a detailed table on microbial growth limits.
ISO 18787:2017: Determination of water activity
This standard is issued by the International Standards Organization. It “gives basic principles and requirements for physical methods of determining the water activity of products intended for human consumption and the feeding of animals.”
Health Canada Compendium of Analytical Methods MFLP-66: Laboratory Procedure for the Determination of Water Activity Using the AQUALAB
Method for measuring water activity in food and food ingredients to determine compliance with the requirements of Sections 4 and 7 of Canada’s Food and Drugs Act.