Testing for Moisture Content In Cannabis
Moisture content is an important check for quality control in the cannabis industry. This metric is important to know when calculating cannabinoid content and evaluating processing techniques, but it is also a vital measure for product safety for both patients and adult use consumers alike.
What is moisture content in cannabis?
Moisture content is the total amount of water present in a cannabis product - the percentage of water retained compared to the overall weight. Moisture is essential for quality cannabis flower, but it needs to be at the right levels to ensure a quality product and a good consumption experience without inviting contaminants to take hold and thrive.
Why too much moisture is bad for cannabis
It’s often said in the cannabis industry that moisture is the enemy of dried and cured flower. That’s because microbial growth like molds and powdery mildew thrive in wet conditions. Once one of these contaminants takes hold, it is difficult to remediate. This can result in several undesirable outcomes for cannabis product manufacturers, including:
Loss of product. If cannabis flower contains too much moisture and microbial contaminants take hold in the product, the whole batch or harvest can no longer be sold as flower, and in many cases, it has to be destroyed.
A reputation hit. If a patient or customer finds the telltale signs of contamination in a product, including a musty smell or visible signs of microbial contamination, that can land a dispensary or manufacturer in hot water as their brand becomes associated with low quality product.
What is the ideal amount of moisture content in cannabis?
Checking for moisture content doesn’t mean that no amount of water should be present in the flower being tested. In fact, too little moisture will leave the cannabis flower too dry, with trichomes that are dried out, brittle, harsh and less effective, which will lead to cannabinoid and terpene degradation. Cannabis products should typically fall between 6% - 15% moisture content, with optimal levels between 6% - 9%. Some say that levels as high as 12% are still acceptable.
No matter what, though, any moisture content higher than 15% puts the product at risk for microbial contamination, mold, mildew, and fungal growth. Anything too low, and the cannabis flower won’t hold together, can crumble with a slight touch, and starts to lose quality.
What does water activity mean, and what does it have to do with cannabis moisture content?
Some may refer to moisture content as water activity and vice-versa, but they are not the same. Water activity is intended to measure how susceptible a product is to potential contamination, while moisture content is the total amount of water in the cannabis itself. They are closely linked, but technically two different measurements.
Expressed as aW, water activity measures the ratio of water pressure of a manufactured cannabis product, like an edible, against the water vapor pressure of water under the same conditions. The preferred way to measure water activity is with equipment called a chilled mirror dew point hygrometers, but may also be measured by capacitance hygrometers or resistive electrolytic hygrometers.
Water activity is a common tactic used to ensure that food won’t harvest microbial growth, and the cannabis industry applies those same tactics to products made in regulated programs across the U.S. and the world. Water activity is checked in many types of cannabis products, including flower and edibles, to ensure that the product won’t spoil or become a breeding ground for microbes. Typically, a cannabis flower sample has to clock in at 0.65 aW or under to pass.
Water activity plays a role in flower quality. Higher than acceptable levels of water activity can cause phytocannabinoids to degrade, lowering the overall quality and potency of the product.
Evaluating water activity is also important for proper long-term storage. If not dried to a sufficient water activity level, smokable cannabis flower may be at risk for developing mycotoxins. Evaluating water activity ensures a lengthy shelf life of the product, confirming that it will stay fresh through storage, transport, and when it makes its way to a consumer’s home.