Water activity can cause expensive problems for food manufacturers including rancidity, vitamin loss, and microbial growth. That’s why it’s important to know the water activity of your products throughout the supply chain and during research & development of new products. The 3 biggest impacts of water on a food product are microbial growth, chemical degradation and physical deterioration including loss of crispness, clumping and caking, and toughness in moist products.

Do you have a means to measure water activity? Here at Nyle Systems, we use the Rotronic Hygrow Palm AW, which is easy to use and costs around $3,300. We use the hand-held meter to measure water activity for samples that we test dry for customers and prospects in our product testing laboratory. Our Rotronic meter has a convenient mobile carrying case, and it has the ability to store data sets into bins to be downloaded and accessed later. With this meter, our engineers can get accurate sample results in less than 10 minutes.

Water activity predicts stability and safety with regard to microbial growth, biochemical and chemical reaction rates, and physical properties. By controlling water activity, you may be able to: maintain the stability of the food; identify the microorganisms that may be potential sources of infection and spoilage; minimize non-enzymatic browning and lipid oxidization reactions; prolong the activity of vitamins and enzymes; and optimize physical properties such as texture and moisture migration.

Water activity, not moisture content, determines the lower limit of “available” water for microbial growth. Since bacteria, molds and yeast require “available” water to support growth, designing a product below a key water activity level provides an effective way to prevent and control growth.

The U.S. Food and Drug Administration has incorporated water activity into safety regulations. For example, 21 CFR 113 states that thermally processed foods are described as being unsusceptible to bacterial growth if water activity is under 0.85 aw. Measuring water activity (aw) can also simplify shelf-life determination, which can help stop product failure, predict and lengthen shelf life, and identify the most cost-effective packaging.