Water Activity Testing

What is water activity testing?

A water activity test checks the amount of unbound water in a food or plant.  Unbound water is water that is not being used by the ingredients in the food or by chemical reactions in the plant itself.  Unbound water can be used by harmful microorganisms to grow and thrive, thus contaminating or destroying the intended product. 

Water activity testing is essential when determining shelf life of products. Overtime, the ingredients or chemical reactions produced in fresh foods will stop using water and thereby “free”-ing it or unbinding it.  Once enough “free” water is available, opportunistic microorganisms, such as yeast, bacteria and molds, will use it to reproduce itself or to produce toxins.

Why is water activity testing important?

This is very important for the cannabis industry as the potential for contamination is severe during the harvesting and trimming processes as this is the time when the most human interaction occurs.  Some microorganisms can survive the drying processes (curing) by going into a “hibernation” state but once there is enough water, microorganisms will continue to grow and may cause harm to patients.

How is water activity measured?

The aW or water activity reading is reported as a decimal amount between 0.0 to 1.0.  The closer to 1.0, the more available water for harmful microorganisms, thereby increasing the probability of having severe contamination on your product.  Most regulations require below 0.65 aW for plants and 0.85 aW for edibles and concentrates.  The amount of available water below 0.6 aW is nearly negligible and therefore harmful microorganisms will have a difficult time growing. 

How do we test for water activity?

We recommend the Rotronic HP23-AW-A for multiple uses in and around the growing, production and testing process.  Use the Rotronic HP23-AW-A for a quick check to see if your plants have finished curing or before sending a batch off to a testing lab.  The HP23-AW-A is a dependable, portable, handheld meter that can quickly read a sample within 5-10 minutes!  Easy calibration, easy use, and easy to set up anywhere makes for easy testing to ensure product safety!