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ATP Bioluminescence Moves Mainstream
Fast, simple test has helped keep food manufacturing clean
by Lori Valigra
Editor’s Note: This article on the history and impact of advances in ATP bioluminescence is the third in a new series for Food Quality. In “FoodTech: Tools That Changed the Industry,” we look at various technologies and tools, such as ATP bioluminescence testing, that have played a key role in and had an indelible impact on the food industry.
Adenosine triphosphate—ATP—is an energy molecule stored in all microorganisms and therefore an indicator of life. That fact did not escape the National Aeronautics and Space Administration, which has long been studying the use of ATP bioluminescence, a reaction similar to the naturally occurring glow of a firefly’s tail, as a way to detect the bioburden on a spacecraft or to search for intelligent life on other planets.
But ATP bioluminescence also has very down-to-earth uses in the food industry as a rapid, simple, and reliable test to monitor surface contamination during processing and to detect contaminants in drinking water or beverages. In the case of surface contamination, a pen-like device containing reagents is simply swabbed over an area, then inserted into a handheld reader that displays results within seconds in relative light units (RLU), indicating clean/unclean and, in some cases, marginal results. The cost is only dollars per test. Since ATP methods only give a broad measure of the presence of organic substances—not the specific microorganism containing the molecule—they must still be used in conjunction with microbial culture or other tests.
“Surface ATP bioluminescence testing is the best proactive tool to assure you are manufacturing food on clean equipment,” said Ken Davenport, PhD, global technical services product specialist in the 3M Food Safety Department in St. Paul, Minn. 3M, which acquired another ATP-bioluminescence company called Biotrace International, has a number of ATP-based products, including the Clean-Trace luminometer that reads the swabs and software that analyzes the data.
ATP bioluminescence began to gain traction over culture agar approaches in the late 1980s, its success prompted, like many hygiene methods, by large, public cases of food poisoning. Initially, the technology was primarily used in laboratories, where suitcase-sized luminometers had to be plugged into a direct power source and required sophisticated users. In the early 1990s, battery power allowed smaller devices to be lugged to manufacturing sites, but they still weighed about four pounds. In the past several years, the technology has evolved into rapid-response handheld readers weighing about a pound.
Now the technology is the darling of food manufacturers. “In North America, 80% of food production facilities are using these,” said James Topper, MBA, market development manager-healthcare at Neogen Corp. in Lansing, Mich. He estimates that more than 80% of European food production facilities are using it as well; the numbers are lower in Asia. Neogen, a former Biotrace distributor, came out with its own AccuPoint ATP Sanitation Monitoring System that uses a half-inch-diameter sponge disk that the company says takes a more consistent sample compared to the cotton-swab-shaped pen tip used by competitors.
“It is a validation of cleaning, of whether equipment is clean enough to be used for production,” Topper said. He pointed to the example of a customer on the East Coast using the system in a baking application. “They were getting higher readings in the morning and weren’t able to figure out why,” he said. Discussions with the user revealed that there had been a change in production. The company was producing something in a different room nearby overnight, and the residue was depositing on the production line, cross-contaminating it. “They wouldn’t have known this was occurring unless they tested with our system,” Topper said.
Martin Easter, PhD, general manager in the British office of Hygiena, a company with headquarters in Camarillo, Calif., said ATP is the first rapid method of any kind to be put into a food application. “This is one of the first rapid methods to withstand the test of time.”
According to Dr. Easter, ATP’s widespread adoption resulted from three major advances. First, the instrumentation decreased in size and increased in performance, utility, and price, like the calculator or mobile phone. Second, the chemistry improved from an initial freeze-dried environment, with 25 tests per bottle and a four-day shelf life after it was regenerated, to its current use of a synthetic enzyme that is more robust and temperature tolerant and can last 12 months. And, finally, the liquid is now stable and is built into the pen-like swab in which reagent mixtures can be snapped and squeezed, then put into a luminometer for readings. Hygiena makes both the Ultrasnap or Aquasnap swabs and SystemSURE Plus palm-sized readers.
Importantly, the technology is much easier to use than it was 20 years ago. “My young son, who is eight years old, tested the counter in the house,” Dr. Easter said. “The technology is more affordable and has been deskilled.”
ATP bioluminescence methods involve the interaction between ATP and the enzyme luciferase. ATP transfers its energy to luciferin to form luciferyl adenylate, which is then oxidized by the luciferase in a reaction that emits light. The light reading intensity is directly proportional to the amount of ATP present: The higher the reading, the more ATP there is. The luminometer detects ATP on a swab using one of two systems: a photomultiplier glass vacuum tube that electronically amplifies the light signal or a photodiode using solid-state semiconductor devices.
Dr. Easter and others emphasize that it is important to use more specific tests with ATP to assure sterile surfaces. “The inside of a tomato is sterile and doesn’t contain bacteria, yet there is a huge amount of ATP,” Dr. Easter explained. “So you can have a huge amount of ATP and no bacteria.” Likewise, it is possible to have bacteria and still get a pass from an ATP system. The test is an indicator of surface hygiene and the potential risk of contamination, but it is not an absolute measure of surface contamination. Bacteria can be present but not show up on the test.
“ATP is not a linear correlation between an RLU and bacteria, so we don’t measure bacteria. We are measuring soil and adenosine triphosphate levels,” said Virginia Deibel, PhD, CEO of TRAC Microbiology Inc. in Monona, Wis., a testing, research, auditing, and consulting company. “You need to set a food safety program in conjunction with ATP. It is one tool in the toolbox.” The United States Department of Agriculture (USDA) and the Food and Drug Administration (FDA) do not require ATP testing because it is so broad, but Dr. Deibel said the FDA likes to see ATP testing during pre-operation inspections after sanitation. “ATP’s greatest strength is it allows the sanitation group to improve their work right away.”
Longer Shelf Lives
One of the first applications of ATP bioluminescence, according to Dr. Easter, was to long-life sterile products like milk. “So instead of milk lasting two to three weeks in the fridge, it could last 12 months in an ambient stable market,” he said. Longer shelf life is a recent trend in a broad array of liquid products, including soup broths that are boxed rather than canned. This makes ATP bioluminescence an important tool in finished product testing, which Celsis in Chicago does exclusively with its CellScan Innovate system for the dairy and beverage markets.
A major trend driving systems like CellScan is consolidation in the dairy industry over the last decade or so. “Now big companies distribute to wider areas, and, therefore, need to increase the shelf life,” explained Scott Scdoris, beverage segment manager at Celsis. The packaging is also different, including cartons containing ultra-heat-treated products that are expected to be sterile. Such products could last up to a year, compared to days or a week with refrigerated products. The Celsis ATP system uses a 96-well microplate to test for contamination. It takes about 24 minutes for the entire test.
The company has a second product that uses the adenylate kinase (AK) enzyme to amplify any ATP that is present. It provides results in 18 to 24 hours and is used to test tea products and some sport drinks. Scdoris said Celsis had the first commercial application for finished product testing using ATP. It absorbed Lumac, a pioneering company in the field. Now, he said, Celsis can test any type of food product that can be put into a liquid phase.
Data for Managers
Celsis and its competitors—both in surface testing and in final product testing—also include software in their products that, in many cases, can be linked to databases to help production managers make decisions and even save money. Celsis says a rapid test system in the dairy industry could save $500,000 over five years.
The Celsis system, for example, has an integrated database that can give sample identification information, identify the product’s production line, and run queries or reports. “This is becoming a big thing in production, with the USDA and FDA taking a much more aggressive stance, requiring manufacturers to be able to access information from individual lots,” Scdoris said.
Meikel Brewster, vice president of sales at Charm Sciences Inc. in Lawrence, Mass., which markets the NovaLUM sanitation control system and PocketSwab Plus, takes it a step further than Scdoris. She points to auditing entities such as the Global Food Safety Initiative as drivers of the technology’s adoption. “With ATP we saw a need—that these auditing entities were looking for sanitation verification,” she said.
As evidence, she pointed to a recent news release from Wal-Mart Stores Inc., which referenced its food safety program achieving “prevention-based certification” against one of the Global Food Safety Initiative’s internationally recognized standards.
“At Wal-Mart and Sam’s Club, our commitment to providing our customers with safe, quality foods is unparalleled,” vice president for Food Safety Frank Yiannas said in the April announcement. “As part of our continuous improvement efforts, we go further than many U.S. retailers in requiring leading-edge food safety standards throughout the entire food production chain.”
Pressure for such testing is also coming from outside companies, said Brewster. “Many food manufacturers are being impacted by their customer requests for audits to be performed. … These audits contain a section for pre-operational inspection. ATP can be used for sanitation pre-operational inspection as well as traditional microbiological testing.” She added that food manufacturing plants are increasing microbiological surveillance on non-food contact/environmental sites. While ATP swabs typically have only been used on food product contact surfaces, she pointed to a trend for customers to use the company’s PocketSwab Plus as a tool in environmental areas.
Looking ahead, companies are moving to improve software features for tracking results and spotting trends. This will tell managers more about what is going on with their production lines so that they can make the critical decisions needed to maintain cleanliness standards and get products out on time. In end product testing, Charm will be releasing a new version of its EPIC microplate luminescence system that can incubate in 36 hours instead of 48 hours.
Other improvements include making surface ATP more sensitive, as well as adding chemistry that could be used with the test to identify some bacteria, although not yet in real time. Hygiena, for example, planned to launch its Microsnap product in May. It is a rapid coliform and Escherichia coli test that can detect any of these organisms in less than seven hours. The chemistry uses a substrate that gives specificity to the organism. “We looked at where else we can take the technology using the chemistry,” said Dr. Easter. “We changed the way we use the chemistry so nonspecific becomes specific and we can detect bacteria. The difference is in the reagent.” The process, he said, is proprietary.
Companies also are looking to new markets, including using ATP in food inspection, fast food restaurants, and health services such as hospitals. ■