Before Water Activity was a required test in the State of Oregon for flower, cannabis testing labs instead conducted microbial screenings that determined how many Colony Forming Units (CFU’s) of mold and yeast were in your product at the exact time it was being analyzed. The regulatory bodies found a flaw with this specific type of testing as petrifilms (a method for detecting spores in product) only gave you a snap shot of what is in your product at that exact time. There was no way to know if this same product would allow microbial growth over an extended amount of time, as cannabis flower can sit in dispensaries or storage for a long period of time, leaving an opportunity for mold to grow. This is why Water Activity is instead conducted on all useable marijuana as opposed to mold/yeast screening as this type of testing gives you a measurement of how much moisture is available for microbes to grow.
Water Activity (Aw) is the measurement of unbounded water within cannabis that is available for microbial growth. At MRX Labs, we use a Water Activity meter that determines the dew point temperature of the sample and translates this temperature to Water Activity by dividing the vapor pressure of water in a sample by the vapor pressure of pure water at the sample’s temperature. In essence, water bound to the surface of large molecules or cell structures is unavailable to microbes, while unbounded water can be utilized by microbes to continue growth. The higher the water activity value, the larger the amount of unbounded water available. The state of Oregon has an allowance of less than 0.65 Aw as fungi requires at least 0.70 Aw for growth.
Our water activity meter operates by weighing out a 1 gram sample in a plastic cup and placing it in the meter. After the meter has reach vapor equilibrium, an infrared beam determines the dew point of the sample using tiny mirrors. The entire process can take up to 10 minutes. This method of analysis has an accuracy of +/- 0.003 Aw and is usually the fastest. Please contact us directly for inquiries or other questions pertaining to this type of testing.