USDA Spurs Food Industry to Use ATP Technology
By Susan English
The food industry is causing a market boom for rapid surface swab technology products that use the enzyme luciferase–produced by fireflies–for detecting the presence of very low levels of contaminants.
Spurred by growing customer awareness and the USDA`s principles of HACCP (Hazard Analysis Critical Control Points), the food industry has been employing a host of diagnostic kits and systems for foodborne pathogen testing since a key element of HACCP is rapid verification of cleaning and sanitation effectiveness.
For those meat and poultry companies that have adopted HACCP, the adenosine triphosphate (ATP) bioluminescence sanitation screen has become an invaluable addition to the battery of tests required to monitor identified critical control points. Unlike traditional swab and aerobic plate techniques, which monitor total viable count (TVC) by taking plate-counts of bacterial colonies after several days` incubation–detecting contamination well after the fact–bioluminescent assays produce real-time results in minutes, allowing for immediate correctability. For the most part, ATP systems are also portable, easy to use, and more cost effective.
ATP bioluminescence technology involves the measurement of light produced by the luciferin-luciferase reaction found in fireflies to detect the presence of ATP, a basic energy compound or metabolite found in all living cells. The reaction of luciferin with the enzyme luciferase in the presence of ATP results in the emission of light. By measuring the intensity of the emitted light with a luminometer, the concentration of ATP in the sample can be determined within minutes and standard calibration curves are used to relate the luminometer readings to the ATP level.
The amount of ATP can provide information on the degree of biological contamination from such diverse sources as bacteria, yeast, mold, plant material, animal material, or some combination of these. High microbial ATP levels indicate that further sanitation is required; ATP from food debris signals the need for rigorous cleaning. ATP, however, cannot indicate the source of contamination, because it counts all materials containing ATP. Traditional plate count methods do not measure food residues, which contain the majority of ATP found in food processing plants. Therefore, a combination of ATP assessment with traditional techniques is recommended for an accurate and thorough assay of type and concentration of contaminants.
According to an industry publication, “The question of whether to conduct environmental monitoring in food processing plants is no longer an issue. Requirements associated with science-based, mandatory HACCP will include standard operating procedures for cleaning and sanitizing. This technology now permits these requirements to be monitored on a real-time basis.” (Scope Magazine, January 1995.) The increased level of hygiene monitoring (HM) throughout industry as a whole, as a result of the broader implementation of HACCP principles and practices both in the U.S. and in Europe, has meant that cosmetics, toiletries, pharmaceutical and biotechnology companies have begun to implement similar HM procedures, increasingly converting to the ATP technology, which detects microorganisms as well as food residues.
According to Dr. Daniel Y.C. Fung, a professor in the Department of Animal Sciences and Industry at Kansas State University (Manhattan, KS), clinical microbiologists initiated rapid methods of detecting pathogens in the mid-1960s because of the need to save lives in hospital environments. But the uptake of the technique was very slow, primarily because of the high capital cost of laboratory-based instrumentation. The development of cheaper instruments suitable for portable, on-site analysis and more cost effective, stable reagents has stimulated recent interest in such applications, particularly in the meat and poultry industries. However, the food service sector, especially restaurants and healthcare institutions, are critical areas where strict monitoring of food preparation practices and the use of rapid, on-site HM systems would be extremely valuable, since most incidents of foodborne illness are associated with mishandling at food service establishments, institutions and caterers.
The ATP Systems
Some commercially available systems are designed to determine the total ATP present and to differentiate between microbial and non-microbial ATP. Systems that measure total ATP are useful in monitoring pre-production cleanliness; those that include procedures for selective detection of microbial ATP have application to in-process monitoring and the analysis of certain raw materials. Kits are available for hygiene monitoring of hard surfaces, including food processing plant and preparation areas; determining the biomass in liquids such as cooling and process water, often used in breweries and wineries; and measuring microbial ATP in raw milk and milk products. Some of the kits resemble a cotton swab dispenser and typically contain: ATP, the luciferin/luciferase enzyme, a microbial extractant, sterile swabs with ATP-free cuvettes and pipette tips, and a luminometer.
Basically, a sterile cotton swab that has been treated with an extractant is used to sample an area of the test item (about 600 cm3). The extractant takes the ATP from microbial cells, wetting the surface of the equipment and allowing free ATP to be taken up into the swab. The swab is then inserted into a clean luminometer cuvette, a buffer is added for dissolving the freeze-dried bioluminescence reagent, and the light output is measured in the counting chamber of the luminometer. Then, the ATP content of the swab is calculated. Some models also include a portable printer, a battery pack and power supply. One model includes a sealed carrying case whose exterior can be disinfected.
ATP Producers
The instrumentation was originally pioneered about 25 years ago by DuPont and others for use in urine analysis in hospitals. However, because of problems with the technology, viable systems were not commercially available until about 15 to 20 years ago, when the Lumac system was developed in Holland. Systems were developed in the U.K., including Biotrace Ltd. (Bridgend, England), BioOrbit, and Celsis International (Cambridge, England). Celsis claims its kits can detect lower levels of ATP than other reagents, allowing the presence of microbes to be determined more rapidly at lower levels of contamination. The company, whose U.S. sales office is in Monmouth Junction, NJ, has also tailored its bioluminescence reagents, making kits available for the food, beverage and dairy industries; hygiene monitoring and end-product testing in the cosmetics and personal care industry; and quality testing in the water industry. It also offers HACCP consultancy and training. Aptly named “The Inspector,” its rapid microbiological testing system features automated injection of luminescent reagent and enables a number of different microbiology tests, including rapid sanitation control checks, rinse water analysis and total bacterial screens. In addition, the system is sensitive enough to be adjusted to accommodate the specific microbial cut-off level for a particular surface or product.
The Bio-Orbit hygiene monitoring system is contained within a carrying case and uses one cuvette and the same volume for all its reagents, reducing the chance for errors associated with changing pipette volumes. The entire test is completed in under two minutes.
One of the most compact systems is the Lightning Swab Device from IDEXX Laboratories, Inc. (Westbrook, ME), the only American-based manufacturer of ATP bioluminescence-based systems. It consists of a swab and a luminometer. The swab is really a self-contained system made up of three components: the wetting agent, the buffer and the luciferin/luciferase. The test procedures are swabbing, then bending one end of the tube to release the buffer, crushing it and squeezing the other end of the tube to release the luciferin/luciferase. Then, the swab tip is inserted into the luminometer and the reading is taken. Lightning results are displayed in “zones” of cleanliness. Photons, the basic unit of light output, are measured by the luminometer and then converted into zones ranging from 0 to 7.5 on a logarithmic base-10 scale as used in the Richter scale. The Lightning has been chosen as an honors recipient of a Food Processing award as having made a significant contribution to the food and beverage processing industry. Presentation of the award will take place at Mega Show in Chicago, IL on November 4-7. n