ATP Assays Point Way to Greater Safety

Food contamination can be a devastating public relations disaster for a food or beverage manufacturer or restaurant. For example, the Michigan-based Bill Knapp’s restaurant chain never fully recovered from a food contamination scandal in the 1990s. Although the cause of the contamination was identified and eliminated, the chain struggled until it finally closed its doors in 2002. An even bigger scandal in 2008, involving Salmonella contamination of peanut products, led to the discovery of major sanitation issues at Peanut Corporation of America processing plants in Blakely, Ga., and Plainview, Texas. The contamination, which sickened hundreds of people and resulted in eight deaths, highlighted the importance of early detection of potential food safety hazards.

Congress is now preparing legislation (H.R. 875) establishing a new food safety administration (FSA) within the Department of Health and Human Services that will, among other things, demand more preventive measures against food contamination, in line with the best current scientific standards.

One of these tools is the adenosine triphosphate (ATP) assay, which tests for food, bacterial, and biofilm contamination on surfaces or in liquids. Once mainly a headache for third-shift cleaning crews, these tests are gaining greater importance as a tool for food quality control and safety. The ATP assay, usually performed as a surface swab, has emerged as an industry standard for detecting food residue or bacterial contamination on equipment and is one of the few tests that can predict a food safety crisis before it actually hits the news. For this reason, there’s a good chance that ATP assays will figure prominently in regulation and inspections under the new FSA.

Manufacturers of ATP tests have responded to increased interest by improving the tests’ sensitivity, accuracy, and ease of use and by bundling them with hardware and software that can more easily accommodate the workflow in a food processing facility.

A Closer Look

All living organisms use ATP for fuel. Because this universal “battery” is found in every living organism, from human beings to fungi, its presence is a good indication of the presence of biological materials. ATP assay technology couples an enzymatic ATP reaction to an indicator reaction. Most ATP assay systems use bioluminescence from firefly luciferase as a signal, which can then be detected by a portable luminometer. The test is nonspecific: It cannot identify the nature of contamination, only its presence.

ATP swabs can be used on many types of surfaces and equipment in a plant, such as conveyer belts, tanks, filler heads, saw blades, and grinders. Liquids can be tested using pipettes or “honey dipper” style devices for tanks and pipes and other types of equipment for which a four-inch by four-inch surface swab would not tell the whole story. A positive test indicates that cleaning was unsuccessful. This may be the result of the cleaning process, or it could be an early warning sign that equipment is wearing out, for example, and can no longer be effectively cleaned.

In the past, ATP assays have been used as a “quick and dirty” post-cleanup procedure, and sensitivity has not been much of a concern. Many plants are using them in a more quantitative fashion now, for collecting and saving data, for tracking trends over time, or as part of a hazard analysis and critical control points (HACCP) process. Because ATP testing is one of the few predictive diagnostic tools available in food industries, it plays an important role in many HACCP programs.

According to Paul Meighan, director for research and development at Hygiena International Ltd. (Waterford, England), HACCP customers comprise the largest portion of their business. Many of these customers require ATP assays that are as sensitive as possible. Hygiena pushes the boundaries of ATP assay sensitivity and accuracy with its forthcoming ultrasensitive Supersnap product, which will detect as few as a thousand bacteria. In order to increase the assay sensitivity, Hygiena used faster enzymes and optimized assay conditions.