CARO’s Water Activity Method for Cannabis Testing

Posted on March 22, 2022

Spoiler alert: this post is NOT about water skiing.

In the scientific world, water activity (aw) is an indicator of the shelf life or stability of a food product.  Water activity finds relevance to cannabis producers as it provides a metric for the likelihood of bacteria growth in your cannabis infused edible products.  The water activity procedure is based on a Health Canada method that CARO has used for years with various non-cannabis food products and is transferable to many variations of cannabis products.

Scientifically speaking, the water activity of a food is the ratio between the vapor pressure of the food itself (when in a completely undisturbed balance with the surrounding air media), and the vapor pressure of distilled water under identical conditions.  In more simple terms, it is the fraction of the water in the product that is not bound to your product, and therefore available to microorganisms to use as they please (and there is nothing they like more than growing!)  Water activity is reported on a scale of 0 to 1.0 – the lower the water activity ratio, the less hospitable your product is for microbial growth.  The table below, borrowed from the Government of Manitoba’s Website, provides a snapshot of the water activity ratios that allow for the growth of some of the more common food-related microorganisms:

So How Does it Work?

Here is a quick break down of CARO’s water activity method in cannabis-based products:

 1. Detecting water activity is actually much simpler than some of CARO’s other methods. To begin, the analyst will calibrate and verify the instrument following proper QA/QC protocols.

2. Secondly, the analysist will ‘prepare’ the sample by spreading it onto a small water activity dish.

3. Lastly, the analysist will insert the sample dish into the detecting instrument.

4. Wait a few minutes for the sample to get a stable reading (this is done in duplicate per sample).

water activity diagram

How the Method is Validated

CARO’s water activity method is validated through a precision and accuracy study. For cannabis specifically, the analyst performs 10 replicates of a matrix or sample.  They will also further verify infused matrices by performing replicates with baked goods, gummies, and chocolates, to make sure the presence of THC/CBD doesn’t cause any issues with getting a water activity reading (we would call these issues “matrix interferences”).

CARO is always researching new methods and applying the most appropriate methods to help you reach your testing objectives.  Our capabilities across a variety of cannabis matrices will provide you with the information you need about your product, so you can be confident that your product is safe as you move into the next steps of production. If you have questions about where to start and what testing to consider for your unique matrix you can go to our client resources page (scroll down to find the Cannabis resources), or reach out to us directly through [email protected].


Richmond, British Columbia

#110 – 4011 Viking Way
#250 – 4011 Viking Way (Corporate Office)
Richmond, BC, V6V 2K9, Canada
Phone: (604) 279-1499 Fax: (604) 279-1599
Email: [email protected]
Monday to Friday 8 am to 5 pm.
Saturday 9 am to 4 pm.
After Hours Emergency: 1 (888) 311-8849


Edmonton, Alberta

17225 109 Ave NW
Edmonton, AB, T5S 1H7, Canada
Phone: (780) 489-9100
Email: [email protected]
Monday to Friday 8 am to 5 pm.
After Hours Emergency: 1 (888) 311-8849


Burnaby, British Columbia

#108 – 4475 Wayburne Drive
Burnaby, BC V5G 4X4, Canada
Phone: (604) 279-1499
Email: [email protected]
Monday to Friday 9am to 8pm.
Saturday 11:30am to 8pm.
After Hours Emergency: 1 (888) 311-8849

    Contact Us

    Yes, I would like to receive exclusive emails from CARO.No, I would not like to receive exclusive emails from CARO.


    Kelowna, British Columbia

    #101 – 3677 Highway 97N
    Kelowna, BC, V1X 5C3, Canada
    Phone: (250) 765-9646
    Toll Free: 1 (888) 311-8846 Fax: (250) 765-3893
    Email: [email protected]
    Monday to Friday 8 am to 5 pm.
    Saturday 9 am to 4 pm.
    After Hours Emergency: 1 (888) 311-8849


    Whitehorse, Yukon (Depot)

    BOX 10 33 Levich Drive


    Whitehorse, YT, Y1A0A8, Canada
    Contact Us for Supplies and Deliveries
    Toll Free: 1 (888) 311-8846
    Email: [email protected]
    Monday to Friday 9 am to 5 pm
    This is a depot with our supplies only. Ship samples to the lab.


    Victoria, B.C. (Depot)

    #3-576 Hillside Avenue


    Victoria, V8T 1Y9, BC, Canada
    Contact Us for Supplies and Deliveries
    Toll Free: 1 (888) 311-8846
    Email: [email protected]
    Monday to Friday 7:30 am to 5 pm
    This is a depot with our supplies and flat-rate next day shipping