What ATP Sanitation Systems Cannot Do

“The residual food or beverage itself can be a problem if there is an allergen cross-contamination concern in the facility,” he continues. “But, the bigger concern is usually what could possibly grow in that food or beverage residue between production runs, and subsequently contaminate food products.”

The RLU result returned through the use of an ATP system can be any combination of benign food residues and more potentially harmful bacteria. For example, one day the tester may get a very low reading, say 100 RLU, which is composed of 10 RLU from bacteria and 90 RLU from food residue. The next day the tester may get a higher reading of 250 that is composed entirely of food residue. If plate counts were conducted using the samples from the two days, the first would yield a high plate count, and the second; a low plate count.

Compounding the issue of correlating plate counts to ATP results is the amount of ATP in microbiological organisms varies significantly between organisms. So a plate count of 50 colony forming units (CFUs) may contain enough ATP to register an RLU of 20 for yeast and zero for E. coli.

“We generally see those performing ATP sanitation monitoring run a complementary program for total or aerobic plate counts,” Topper said. “These testing approaches give us a better picture of a production facility’s sanitation level and issues. The specificity of determining what microorganisms may be contaminating the product can provide the information needed to investigate their source. Sanitation is not always the problem. For example, rigorous sanitation cannot undo a raw ingredient that was contaminated with mold when it arrived at the facility from a vendor.”

Some companies have taken the approach of comparing ATP readings before and after a bacterial lysing step. The theory with this approach is that any ATP detected in the “after” reading in excess of the before reading would have to be from a bacterial source. The problem is that, in practice, there are too many variables that render this approach impractical. One of these variables is the potential for significant sampling variability, and another is the amount of time needed to lyse various bacterial cells. The amount of time it takes to lyse a yeast cell varies significantly from that of an E. coli cell. The wall structures are very different.

ATP Testing a Poor Tool in an Allergen Control Program

Another misconception that seems to have been gaining in popularity lately is the idea of using ATP sanitation monitoring systems as part of food allergen control programs. The theory here is that if all or most of the ATP on our surface or in a CIP system has been eliminated, all of the possible allergenic protein has also been eliminated.

“There are at least a couple of reasons why this is a very bad idea. First, allergenic protein can exist on a surface at up to 100 times the level of concern and still be below the detection level of any ATP system,” said Topper. “Secondly, like the rationale on why you can’t determine the level of bacterial ATP from a result from an ATP sanitation monitoring system, you can’t know how much of an ATP result is from an allergenic protein and how much is from something else.

“So, if we set a very low fail limit with our ATP system, we may end up cleaning more than we have to,” he continued. “The cleaning process may remove the allergenic protein more effectively than the other organic matter. If that’s the case, a company could have spent a lot of time, energy and money cleaning beyond what was necessary.”