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What ATP Sanitation Systems Cannot Do
ATP Systems are not Designed for Total Plate Counts or Detecting Food Allergens
by Dan Leblanc
Screwdrivers are designed with the intent to do one thing well: Drive screws, but the designers’ intent doesn’t stop screwdrivers from being used poorly as chisels, pry bars, door knobs, fondue forks, lawn darts, etc., etc. Likewise, ATP (adenosine triphosphate) sanitation monitoring systems are designed to do one thing extremely well: Detect and measure ATP on surfaces and in liquids as a method of determining the relative cleanliness of the surface or liquid. But the designers’ intent doesn’t stop ATP sanitation monitoring systems from being used poorly as methods of determining a food sample’s total microbial plate count, or detecting an unlabeled food allergen before it can contaminate a non-allergenic food.
“I spend a great deal of time working with food safety professionals to help them understand what ATP sanitation monitoring systems can do for their operations, and then assisting them to implement the systems into their facilities,” says Jim Topper of Neogen Corp. (Lansing, Mich.) “Properly utilized, sanitation monitoring systems allow for the almost instantaneous detection and measurement of ATP on food contact surfaces, which provides an objective, actionable tool for monitoring of a facility’s sanitation efforts.
“ATP systems provide immediate feedback on whether a facility’s sanitation efforts have been thorough enough to prevent the accidental contamination of its products with residues from previous production runs, or the microorganisms that they may harbor,” Topper continues. “The potential consequences of shipping contaminated product are well documented. But as obvious as the advantages of using an ATP detection system seem to be, I routinely spend a lot of time with food safety professionals to help them understand what ATP detection systems cannot do well.”
What ATP Sanitation Monitoring Systems Detect
ATP is the energy source in all living cells. Since virtually all of the food and beverages produced were once living, they contain ATP. Microbiological organisms, like bacteria, yeast and mold, also contain ATP. As a mixture of food, beverage, and microbiological material comes into contact with pipes, tanks, and food and beverage production surfaces, it leaves its ATP on whatever it comes into contact with.
In very simple terms, ATP sanitation monitoring systems detect the amount of organic matter that remains on food contact surfaces, in liquids, or on pipes, tanks, etc., after a company has completed its sanitation efforts. The amount of ATP detected, and where this ATP was detected, signals company personnel of possible trouble spots that may need to be resanitized prior to the start of the production cycle. Simply detecting excessive amounts of ATP, however, does little to definitively identify the source of the ATP. ATP sanitation monitoring systems are not designed to differentiate between the various sources of ATP.
“The more ATP that is present on the sampling pad when it interacts with the reagents in the sampling device, the more light that is created, and the higher the reading that the system’s luminometer will return. It’s that simple,” Topper says. “But, to the reagents universally used by such systems, ATP is ATP. Period!”
ATP sanitation monitoring systems are easy and quick gauges of a facility’s cleanliness, which are easily customized for the specific equipment, people, product, and processes used in any food production facility. The systems set an objective, recordable, and traceable standard to help avoid the consequences of substandard sanitation efforts.
ATP Results Do Not Correlate with Microbial Counts
It is a common misconception that the results received from ATP testing systems in relative light units (RLUs) for surface samples, for example, should in some way correlate with a microbial total plate count result for the same samples.
“Some of those I work with would like these ATP systems to be more specific, but they are not. They are strictly about telling us how well we’ve cleaned,” Topper says. “You could have an extremely high RLU reading that, in fact, detected the ATP from very few microbes. Inherent in our cleaning process is the need to minimize the risk of microbial growth and cross-contamination. That’s why we clean.
“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.”
It’s easy to understand why those in the food industry would want allergen and bacterial detection tests to be as easy and quick as ATP monitoring systems. The ease and speed of ATP systems are two of their most valuable features. The ability to find out immediately that sanitation efforts have not reached the performance standard provides the capability to correct that problem—before the problem can become much larger.
Dan LeBlanc is a writer for Neogen Corp. (Lansing, Mich.). Reach him at 800-234-5333, ext. 247 or firstname.lastname@example.org.