As published by Food Industry Executive — March 29, 2022
The public is used to recalls tied to high-moisture foods such as melons, lettuce, and ice cream. But many people were shocked by the 2018 Salmonella outbreak attributed to Sugar Smacks cereal, the 2019 Salmonella outbreak tied to flour, and the 2021 E. Coli outbreak tied to cake mix. The assumption that there is no risk of microbial contamination in low-moisture and low-water activity foods has led to numerous foodborne illness outbreaks and recalls.
So why does the FDA use water activity limits as an acceptable standard to qualify for limited or no microbial testing in shelf-stable foods?
Before diving into this question, it’s important to note that moisture content and water activity are related but different concepts. Moisture content is a measure of how much water something contains. People often think of foods as “dry” or “wet,” but their capacity to support microbial growth doesn’t depend on how much water they contain. Instead, it depends on the energy, or water activity, of that water.
Moisture content and water activity differ from each other because …
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