Making the right choice

by Martin Easter, Hygiena International

Martin Easter of Hygiena International explains what to look for in an ATP hygiene monitoring system.

“The most important features [of ATP system] are repeatability, sensitivity and accuracy, as well as robustness, low capital cost and maintenance costs.”
-Martin Easter, Hygiena International

How do you choose the right ATP test system that delivers both performance and value for money?

John from Norfolk writes: I need a rapid test to verify the hygienic status of my food processing equipment and facility. I understand that there are several suppliers who make various claims about their product and other suppliers. Where can I get an unbiased opinion and what should I look for in an ATP hygiene monitoring system?

Martin Easter replies: Adenosine Triphosphate (ATP) bioluminescence is a technique that has been used as a monitor of the hygienic status in food production facilities since 1980. The application of ATP hygiene monitoring is intended as a direct, objective test of cleaning to verify the removal of product residues. This biological test has exquisite sensitivity but has a natural variability. Accordingly, the hygiene monitoring application is not intended to be used as a precise determination of ATP content. The results from ATP surface hygiene monitoring are different to those of microbial enumeration methods and give additional information that the microbial test cannot provide. ATP tests are not intended to replace microbial tests but there is concurrent direct correlation between the results of the two methods because cleaning simultaneously removes both organic residues and microbes.

The components of ATP systems include instrument, its detector, and the reagents that are finely balanced. These determine the background noise and performance characteristics of the system. The most important features are repeatability, sensitivity and accuracy, as well as robustness, low capital cost and maintenance costs. Modern solid-state systems can deliver great performance but also great value because they are low cost, low voltage, and stable.

The largest ever laboratory study of commercially available ATP hygiene monitoring systems was conducted by a leading independent food safety and quality laboratory. The comprehensive study generated over 5000 results and it determined linearity, repeatability, and sensitivity of six systems from leading suppliers when tested against ATP, microbes and a variety of foodstuffs over a wide dilution range.

Statistical analysis was applied to the results, which are summarised in the Table below. Neogen and Charm ceased to become linear below a set RLU threshold where only zero RLU values were displayed by the instrument. These systems also showed the highest amount of variation with CV of 86 and 123 percent compared to the average for the technology of 26 percent.

The limit of detection of Kikkoman, Neogen and Charm systems was 10 fmols ATP, which is not sufficient to meet typical industry Pass levels of five to 10 fmols ATP.

BioControl and Charm have high RLU outputs per unit of ATP but this high RLU does not impart greater sensitivity or better performance to the system.

3M CleanTrace and Charm systems were the least accurate in that they detected only 50 percent of the sample.

The most precise, accurate and repeatable systems was the Hygiena SystemSURE Plus with either Ultrasnap or Supersnap swabs with CV of nine percent and sensitivities of one and 0.17 fmols ATP respectively.

Dr. Martin Easter is an expert in rapid microbiological testing. Working in the fields of food safety and quality management he has managed several government funded research programmes. As General Manager for Hygiena International he directs all business development activities to bring the market new and convenient test methods.