ATP Assays Point Way to Greater Safety

“You either make the instrument more sensitive or the chemistry more sensitive,” Meighan said. Although more sensitive luminometers are available, focusing on the chemistry helps to keep the costs down for the end user. “The enzymology has reached maximum physical and kinetic output. The next stages are to now look to more sensitive luminometers as we at Hygiena are doing….The time will come where the ATP bioluminescence test may be as sensitive as it can be, at the attomole detection level now with only 6 logs to reach Avogadro’s number [single molecule detection].”

Meighan added that the main problem with sensitivity is not output of relative light units (RLUs) but the background noise. “If everything contains ATP, then all chemicals that go into ATP reagents will have intrinsic ATP which creates a signal above which is your measured signal. This is the battle that Hygiena has waged and now has won with backgrounds not measurable.”

Hardware and Software

Charm Sciences (Lawrence, Mass.) manufactures the swab kit and hardware components of their ATP assays and luminometer instrument and also develops the software and firmware. The vertical integration structure allows them to control every aspect of the product. One of the main innovations at Charm has been a wireless option on the luminometer that transmits ATP data in real time during the pre-op sanitation. This eliminates the sometimes lengthy delays involved in hygiene testing in a large plant.

Even with the sophisticated software and hardware environment, sensitivity is important. “It’s important to use a test that gives you confidence in your sanitation program,” said Gerard Ruth, Charm’s vice president. “If you’re using a test that’s insensitive, you have a false sense of security. It’s important to use instruments and tests that will allow for continuous improvement and not be satisfied with a test that fails to detect critical levels of ATP.”

Accuracy is a critical concern with an ATP device. All ATP tests are capable of detecting pure ATP. In nature, however, ATP occurs within a biological matrix, often inside bacterial membranes or behind the cell walls of plants and animals. In order to ensure reliability inside the manufacturing facility, some attention must be paid to the type of testing being done, the kinds of residues likely to be found, and the ability of a particular device to be accurate in detecting ATP within that context.

“Some ATP systems work beautifully with pure ATP and much less reliably in real world situations,” says Ken Davenport, PhD, Global Technical Services Product Specialist for 3M. “The industry is becoming more aware of those situations and becoming more discriminating in … manufacturers for swabs.”

3M also includes a robust software package with its rapid hygiene ATP testing product, Clean-Trace. This software allows the user to create sample testing plans and group testing points together. The sample plans are transferred to the portable luminometer, where data is collected and transferred back onto the system. The system can then track the data and generate reports, graphs, and other types of analysis to help with decision-making in the plant. “It’s more than just an instant pass/fail,” Dr. Davenport said. “It’s being used to really track what’s happening in the plants. You get more value out of your ATP testing dollars using software to understand what’s happening in the cleaning process.”

ATP testing is not a solution for every problem in food quality and food safety, but it can be used to predict and prevent certain kinds of problems. Food residue that remains on a surface after cleaning can become a food source for microorganisms. In addition, off flavors or cross contaminations by allergens can result from failed cleaning processes. In the case of the peanut contamination scandal, a single source of contamination affected dozens of products distributed all over the world. Peanut products are not usually subject to pathogen testing because they have low water content. However, a regular program involving ATP swabbing of equipment and surfaces would surely have revealed the presence of animal feces in the plant. Thus, a predictive approach to hazards using tools that cast a wide net, like ATP testing, could theoretically avert unexpected hazards.