Microbial Growth in Packaged Cannabis Products
Occasionally, regulators may come across contaminated products like flower and pre-rolls on the shelves, despite these lots having previously met state standards. Often, this anomaly can be traced back to post-harvest environmental control.
The key metric here is water activity, a measurement that indicates the likelihood of continuous microbial growth, even in a packaged state. For example, let's consider a plant material that passes the 10,000-count-limit test with a count of 7,000. If the water activity is out of spec, this count could double over a few weeks, resulting in non-compliant material. To prevent such microbial growth post-packaging, 11 of 29 states now mandate the testing of water activity, and we foresee other states soon following suit.
In California, the upper water activity limit for flower is established at 0.65. If flower material is not cured to a water activity measure of at least 0.70, it can promote the growth of yeast and mold. With strict water activity limits set for packaged cannabis, the scenario of microbial contamination, such as the recent incidents in Denver, can be prevented.
But how do you maintain a desirable water activity of ≤0.65 post-harvest? It requires dedication, team cooperation, and rigorous standard operating procedures (SOPs). All post-harvest processes should ideally be performed in a controlled environment where the relative humidity (RH) is kept between 55– 65%. Achieving a stable humidity (equilibrium relative humidity, ERH) across all post-harvest processes is crucial.
To accomplish ERH, monitoring and controlling potential humidity effects due to weather, temperature, and personnel traffic in your processing rooms are necessary. Well-implemented practices, solidified in your SOP, ensure you're taking every step to maintain the required water activity, thereby eliminating microbial growth in the packaged products.
bIn the packaging phase, microenvironment control can be achieved using relative humidity control packets like Boveda and Integra brands, which are designed to maintain an internal package humidity of 62%. These packets absorb and release water based on relative humidity, mitigating temperature fluctuations and maintaining a microbiologically stable cannabis product with an extended shelf life and a yeast and mold count compliant with state-mandated tests.