Water Activity Testing

According to fda.gov website, “The water activity (Aw) 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. A water activity of 0.80 means the vapor pressure is 80 percent of that of pure water. The water activity increases with temperature. The moisture condition of a product can be measured as the equilibrium relative humidity (ERH) expressed in percentage or as the water activity expressed as a decimal.

Most foods have a water activity above 0.95 and that will provide sufficient moisture to support the growth of bacteria, yeasts, and mold. The amount of available moisture can be reduced to a point which will inhibit the growth of the organisms. If the water activity of food is controlled to 0.85 or less in the finished product, it is not subject to the regulations of 21 CFR Parts 108, 113, and 114.

What types of food can be tested?

– Dried Fruits
– Beef Jerky
– Peanut Butter
– Flours, rice, beans, peas
– Sausages, syrups
– Cookies
– Moist Cakes
– Butter Cream Frosting
– Biscuits, chocolate
– Salami
– Gummy Bear Candy
– Jams and Jellies
and the list goes on!

The Wisconsin Cottage Bill – According to the Wisconsin Cottage Food – Best Practices for Selling Baked Good’s Website, “A non-potentially hazardous baked good is one that can safely remain unrefrigerated and do to support the rapid growth of bacteria that would make people sick when held outside of refrigerated temperature. Lower-risk food means food in a form or state that is not capable of supporting the growth of disease-causing organisms or the production of toxins.

Click on the link for the Wisconsin Cottage Food Form