Water Activity and FSMA

Learn why water activity is an ideal preventive control under FSMA, working in HARPC risk-based programs to prevent microbial growth.

The Food Safety Modernization Act (FSMA) has shifted the food safety system in the U.S. to preventative measures as opposed to reactionary measures. In other words, instead of focusing on how to react to foodborne illnesses, our focus now is to take the necessary steps to prevent foodborne illnesses. Water activity is an ideal measurement to use to keep food safe. 

A Risk-Based Approach

Under FSMA, all food producers need a food safety system in place to conduct hazard analyses, develop preventive controls, monitor processes, take corrective actions as needed, and verify the program's success. By creating this type of system, food producers can have preventative controls in place that allow them to identify the areas of most significant risk and take corrective actions immediately if breakdowns occur. 

Water Activity and Food Regulations

Although water activity has been a part of food regulations for a long time, it is more relevant and essential than ever before in this preventative space. Water activity has always been a preventive, not reactive, measure, making it a perfect fit in today's food safety programs. 

With this in mind, it's essential to understand that managing water activity is not a kill step. Instead, it is a step that keeps food safe by preventing microbial growth. It is also critical to remember that measuring moisture content does not predict microbial safety, nor does it guarantee that FSMA requirements are met. 

Figure 1. Water activity has long been a part of federal food regulations and has increased significance under FSMA.

The Epitome of Prevention Control

Managing water activity levels in food products is one of the most straightforward and effective ways to keep food safe. This is because water activity is easy to measure and results in an accurate, productive understanding of how critical water activity levels prevent microbial growth. 


Water activity levels can be easily monitored and verified with the proper instrumentation – sometimes in as little as five minutes. Data is simple to gather and easily implemented in food safety programs. 

Critical water activity 

All organisms have a critical water activity level where they can no longer access water to go through their metabolic state. Thus, they enter a stage of dormancy. In the dormancy stage, organisms such as bacteria, mold, and yeast are not actively growing and cannot cause infection or illness. Therefore, by identifying each organism's critical water activity level, you are not killing the organism but can effectively prevent it from growing and stop its ability to cause illness.

Figure 2: Each organism has a critical water activity level where it enters a state of dormancy.

Hurdle Technology and Interactions

Correctly understanding and monitoring water activity also allows you to implement hurdle technology when necessary. Sometimes controlling one factor, or one hurdle, that influences microbial growth is enough to stop the growth and prevent spoilage or contamination. At other times, it takes more than one hurdle to create a synergistic effect that will impede microbial growth. This is called the hurdle effect. Examples of hurdles are temperature, refrigeration, pH levels, redox potential, preservative, competitive organisms, vitamins, nutrients, and water activity. To successfully prevent microbial growth, you need to have enough hurdles or a high enough hurdle, to stop a microorganism from growing.

Understanding the interactions between water activity and pH levels can also be instrumental in hazard and risk analysis for the product, both inside and outside its package.

Figure 3: Understanding interactions and hurdles is essential to risk and hazard analysis.

Water Activity in Food Code and Safety Systems

It's clear that water activity measurements, which have long been a part of food codes and regulations, are also a critical part of food safety systems that include hazard and risk analyses.

Sign up

Case studies, webinars, and articles you'll love.

Receive the latest content on a regular basis!

By submitting this form, I agree with the Addium, Inc. privacy policy statement.