Water Activity and Cannabis

Water activity, relative humidity, moisture content – find out which one does what, and which will make the greatest impact on the quality and consistency of your product.

The drying process for cannabis is essential and delicate. Over drying can destroy trichomes and hurt profits. Under drying can lead to mold, sick customers, and a damaged reputation. With a tight moisture target to hit for an optimal product, understanding the effects of moisture content, relative humidity, and water activity is essential. Read on to learn which moisture process has the most significant impact on quality and consistency. 


Preventing Microbial Growth

Preventing mold and other microbial growth in cannabis is essential to quality assurance. While many molds will not make healthy individuals sick, inhaling molds spores can cause fungal infections in the lungs and be particularly dangerous for immunocompromised consumers – many of whom use cannabis for treatment. 

The key to preventing microbial growth is understanding and managing water activity. Each organism has a critical water activity level where it will not grow. Therefore, maintaining a suitable water activity prevents microbial growth, keeps the product safe, and is essential to government guideline compliance. 

Although it is tempting to use moisture content as a primary moisture measurement, this should be avoided. Moisture content is a less accurate moisture measurement for cannabis because there is no industry standard for what is "dry." With cannabis, the weight loss in the heating and drying process is not only water but also terpenes and flavonoids. 

Moisture content, however, does have its place in moisture measurement. The relationship between water activity and moisture content is shown through a moisture sorption isotherm which indicates that small changes in moisture content cause significant changes in water activity. Using the moisture sorption isotherm will give you a very accurate and specific moisture measurement of how moisture will affect your product. 

It is also important to remember that water activity is temperature-dependent and that, generally, higher temperatures lead to higher water activity. Higher temperatures also lead to increased rates of decarboxylation. With this in mind, it's wise to give yourself a little leeway in the product's water activity level and relative humidity in case it experiences temperature abuse after packaging. 

Figure 1: Maintaining critical water activity levels prevents microbial growth.

Moisture and the Drying Process

Relative humidity and water activity must also be managed during the drying process. Over drying is sometimes done to avoid safety issues or because the RH of the cannabis is unknown. However, over-drying can lead to a loss of quality and profits. Under drying also presents serious issues as it can lead to mold and other microbial growth. Monitoring water activity and relative humidity during the drying process will allow you to hit the sweet spot where microbial growth is prevented and weight and quality are protected.

Figure 2: Monitoring water activity and relative humidity in the drying process will allow you to avoid over- or under-drying your product.

Preventing evaporation

Another aspect of protecting the quality of cannabis is packaging. Packaging that can effectively control the relative humidity of and around the cannabis is vital to preventing evaporation post-harvest and throughout the supply chain until it reaches consumers. 

Boveda produces two-way humidity control pouches for cannabis to ensure the product's maintained ideal equilibrium relative humidity. The correct RH creates a monolayer of water to protect the trichome head so terpenes and cannabinoids don't evaporate, ensuring the quality of the product is protected until a consumer opens and grinds it. Avoiding unwanted evaporation also prevents a loss of water weight that could result in a loss of revenue. 

Figure 3: It is critical to cannabis quality to prevent post-harvest evaporation.

Quality, Reputation, and Profits

Managing moisture in cannabis should be a critical priority in producing cannabis. Managing water activity properly and choosing the correct packaging to maintain the desired RH will ensure a safe, high-quality product. Controlling moisture correctly also protects the product's weight, which is vital to profit revenue. And all of these processes and outcomes lead to protecting your brand and reputation. 

For specific water activity and RH levels recommended for cannabis, please watch the entire webinar above.

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