PRODUCT SAFETY and quality is the bottom line.  Spoilage and poor quality hurt or destroy sales. You set quality standards and stay within them.  But where do you set the standard, and how much of a safety margin do you need? Too many manufacturers measure moisture content and use a by-guess-and-by-golly standard.  For example, a pet food manufacturer we know was producing to 8% moisture content.  Why? Because at that level, he had never had spoilage problems or shelf life concerns.  He had a safe product. But he discovered that he was drying up profit.  Then he used water activity measurements to get a more accurate food quality picture.  The water activity of his product was 0.50 aw.  A little additional information revealed that he needed only to stay below 0.65 aw to produce a quality shelf stable product that was below the mold growth limit.

Without knowing his exact costs, we can still infer the profit margin represented by a difference in 0.50 aw and 0.65 aw.  If he produced 20,000 pounds of product per hour, operating sixteen hours a day five days a week, and sold the product for forty cents a pound, raising the target aw level would allow him to produce an additional 1,877,314 pounds of product per year and would generate an additional $750,925 in revenue.  Even better, much of that would be profit since this change would reduce utility costs while keeping man hours, raw material costs, and wear and tear on equipment the same.

Just a tricky little story problem?  Not at all.  Many manufacturers have decreased costs and increased profits using water activity.  Moisture content measurements just can’t give you the safety and quality information you need.  Knowing water content reveals nothing about the total food quality picture.  Good operating decisions can only be made using good information.  Usually, water activity is one of the best pieces of information you can have in setting and maintaining food quality standards. 

The food industry, together with the FDA and USDA is adopting a system to improve safety and reduce the incidence of food-borne illness. The Hazard Analysis Critical Control Point program (HACCP) involves setting critical control points that measure food quality throughout production.  Rather than “check-and-chuck” at the end, these critical control points detect problems all along the production line.  Water activity is a critical control point in many processes.  It defines critical limits for microbial and chemical parameters which must be controlled to prevent food safety hazards. 

Even when safety isn’t an issue, water activity is an important measure of quality.  You can set critical control points to avoid loss of crispness in dry products, caking and clumping of powders, tough and chewy textures in moist products and shortened shelf life.  Water activity is a powerful number.  Measure and manage it, and you gain control over the quality of your product.  You can produce a consistently high-quality product and meet expectations without having to throw away mistakes—and you won’t need a huge safety margin that wastes potential profit.