When first shift arrives for the days’ production at the typical food manufacturing plant, line operators and managers see a gleaming, shiny line ready for the day’s work. If third-shift sanitation crews have done their job well, the plant environment—floors, walls, celings, etc.—and processing machinery will appear clean and sanitary at first glance. However, looks can be deceiving. Microorganisms, biofilms and chemical residues can survive the sanitation process if cleaning and sanitizing procedures have not been adequately followed. While the plant and equipment may appear to be clean and free of gross soils, how do we know that sanitation has been effective in removing potentially harmful microorganisms and other food contaminants that are not readily visible on plant surfaces?
Even with the most effective sanitation standard operating procedures (SSOPs) and highly dedicated sanitation crews who follow these protocols to the letter, it is important to institute a comprehensive environmental hygiene monitoring and testing program that verifies that the processing plant is as clean as it looks. The fact is that the sanitation department has only as much time as the operations and production departments give them to complete its job. No one makes money if the lines aren’t running but if the sanitation crew has to rush cleaning activities, those lines are probably not going to be as clean as they look and may not in fact be fit for production. Environmental hygiene monitoring and verification testing is not only important to ensure that cleaning activities were effective, but provides valuable data to the operations and production departments for use in establishing cleaning schedules and a departmental budget that facilitates adequate cleaning and maximizes production time.
Ultimately, the investment made to strengthen the sanitation program pales in comparison to the costs associated with ineffective sanitation to the company—production line shutdowns, product recalls, damage to the brand and potential litigation. Verifying that your sanitation program is effective is essential to ensuring that the investment you’ve made is sound and that the foods you manufacture are the safest possible. To get the most out of the environmental hygiene monitoring program, processors will want to conduct pre-operational monitoring, determine the locations, frequency and methods of sampling, and identify the appropriate screening and testing technologies for verification of sanitation efficacy.
Strategic Sampling is Key
Developing an effective environmental sampling and testing approach for a food processing plant involves conducting pre-operational monitoring to collect data that will provide a database for good decision making, Conducting a pre-op sanitation audit helps to identify hotspots in the plant, the appropriate cleaning and sanitizing agents and methods, and the frequency and type of sampling and testing to be used to monitor and verify efficacy. Importantly, pre-operational environmental sampling allows the company to identify specific microbial counts that can be used to establish a cycle for sanitation periods that maximize production and provide an environment and equipment that will produce safe and wholesome food.
This audit is especially important if the facility is manufacturing ready-to-eat (RTE) meat, seafood, juice or other products that are determined to be high risk since the resulting data will provide the basis for developing effective corrective actions and indicate more frequent sampling and verification of environmental surfaces than is needed on a low-risk product processing line.
The next step is to develop a strategic environmental sampling strategy. Food processors conduct environmental sampling either as part of routine surveillance of sanitation program effectiveness or as part of an investigation into an unusual circumstance, such as high microbial count readings in an atypical area of the plant. Typically, the routine surveillance focuses on areas identified as hotspots during the pre-operational monitoring audits. The quality of your sampling strategy—what, where, when, how much—will directly impact the validity of your environmental monitoring program and the interpretation of results.
What to sample depends on the layout of your facility, the product being manufactured and the type of processing line on which product is run. You need to know whether a product is considered a low-level risk for microbial contamination (i.e., baked goods) or high risk (i.e., RTE meat or soft cheeses, etc.). Products containing allergens such as peanuts or milk that are manufactured on the same equipment as non-allergen containing product will also pose additional risk and may require a specific sampling protocol. The sampling strategy will be different if the process itself involves one or more kill steps versus a minimal processing operation in which there is no cooking or other microbial intervention in play.
The processor also needs to know the intended use and even the target consumer group who will use the product to select the right sampling technique and frequency. Is the product going to be remanufactured? For example, raw cookie dough sent to a customer who bakes it for use in cheesecakes is a lesser risk than dough sent to an ice cream processor who uses it as an ice cream inclusion. The latter scenario is a higher risk proposition since the raw dough is put into into ice cream that has already been pasteurized. Higher risk products will require more frequent or intense sampling programs to ensure sanitary operating requirements, which are frequently required by customers.
The locations that you choose to sample are critical, and as a general rule, it is important to look for trouble. Actively searching out the sorts of environments that microorganisms prefer gives you a better opportunity to find hotspots before they find you and before they can establish a niche that could take up more of your valuable resources to eliminate them. If you find positives for microbial or other contamination, you will be able to concentrate cleaning and sanitizing efforts to eliminate them or experiment with other mechanical cleaning measures or sanitizing agents to remove them.
In the processing facility, consider the location of production lines and traffic patterns when deciding where to routinely sample. For example, what is the relation of the garbage dock and loading dock in relation to the production line? Does it involve heavy traffic patterns that could allow undesirable organisms to migrate to production areas? If so, those areas should be routinely sampled. The movement of support equipment is often a big culprit in the transfer of food contaminants from non-production to production areas. Production support equipment such as floor scrubbers, forklifts, pallet jacks and wheeled trash bins should be sampled and screened to ensure that they are clean and sanitary as they move throughout the facility.
Even production support equipment that doesn’t move, such as compactors, can be a potential hotspot for environmental monitoring and sampling. For instance, compactors often retain food waste and moisture in and around their frames and entrances to freezers typically have some condensation, which provide a growth environment for microorganisms. While these areas are not normally considered a risk, they are support equipment to which many other moveable support equipment interact and thus could transfer the microorganisms. Employees’ boots and shoe soles are other items that should be sampled occasionally to ensure that bootwashers or sanitary dips are being used to prevent migration of bacteria.
On production line equipment surfaces, samples may be taken from two areas. Food contact surfaces, if they are swabbed, should be sampled after the cleaning and sanitation processes have been completed and prior to starting up the line. If your program includes monitoring of food contact surfaces, you must ensure that you follow your sampling by thoroughly re-cleaning and re-sanitizing the areas. If you don’t, the implication for production is that you may have inoculated your product with your line.
The second area in which to concentrate sampling is areas of production where microorganisms or other contaminant-like allergens could migrate from non-contact areas to food contact areas. This includes floors, framework, insides of guards, hand tools, and other places on or within equipment that support the production line. Cleaning processes are concentrated on product-contact surfaces and equipment especially when the sanitation teams are rushed by production schedules, but if you neglect the supporting areas, equipment and components where cleaning processes are less concentrated, contaminants will gain a foothold and can migrate to product contact areas.
Environmental hygiene monitoring should also include air sampling. Many experts note that airborne contamination is strongly suspected as the cause of some pathogenic contamination. Microorganisms exist in the air as passengers, within condensation droplets and as isolated organisms. Other airborne contaminants include water, gases, viruses, yeasts and molds, pollen and chemicals. Air sampling devices are available from several technology suppliers, including units that utilize media strips or plates that capture such contaminants in a given volume of air. Some specialized plates can be used in passive air sampling procedures; i.e., without the sampling device. These sampling methods are easy to teach personnel to use and simple to operate.
As with other types of environmental sampling, effective air sampling requires you to consider the climate in which the plant is located and the frequency at which samples should be taken. If the facility is located in the desert Southwest, for example, you would expect to see less yeast and mold in the air than in South Carolina during hurricane season, when the climate is warm and humid. External air that is pumped into and circulated throughout the plant will have varying amounts of naturally occurring yeast and molds. It is important for you to establish what this level is each time you take air samples to establish whether your results are normal or if you have an issue that has elevated the populations. The frequency of sampling plant air and air handling systems will be dependent on the effectiveness of the air filters, the amount and quality of air that the system handles and whether there are problems detected within your established filter changing schedules.
Beyond the routine hotspots, it is very important to perform environmental and air sampling when you see something unusual happening in an area, particularly if you’ve never seen a specific contaminant in that area before. By investigating atypical environmental samples, you will be able to ascertain whether it is a fluke or not; and if not, find the root cause and correct the problem. The following is a good example: At one plant, the environmental air sampling revealed increased levels of airborne yeast beyond normal levels, and normal was few or none. As yeast levels ramped up, quality assurance personnel investigated and began sampling more locations until air sampler readings narrowed it down to a specific area of in the facility. Upon looking at the air handling systems in that location of the plant, the investigators discovered a large mass containing yeast and mold in an air duct.
What had occurred? In an effort to create utility savings the maintenance and engineering departments had made modifications to the air systems. The original system supplied 100% fresh air from outside the building. In warm months, it was expensive to cool, and in the winter it was more expensive to heat. Their solution was to change the duct work and circulation systems to mix air from inside the facility with make-up air from outside the facility. However, the new system had introduced a lot more moisture into the air ducts in the form of steam generated during sanitation activities. This retained moisture in the air handling systems, which in turn created a very nice, warm place for yeast and mold to grow. The plant solved the problem by installing a switch for 100% make-up air circulation during sanitation cycles. The result was a dry air system free of yeast and mold, and significant utility savings.
Rapid Tests for Verification
Some of the most useful developments in the area of environmental hygiene monitoring tests have been made in the area of rapid methods used to sample equipment surfaces to monitor the efficiency of sanitation procedures in the plant. The advantages of such rapid methods over conventional swabbing followed by standard aerobic plate count techniques are numerous, including the near “real time” results provided, increased sensitivity and good reproduceability. Many of these rapid methods also offer processing plants reduced time, labor, training and associated costs, and improved accuracy.
Today, the rapid methods used for sampling equipment surfaces are based on a variety of test formats and techniques that have been proven successful in monitoring for sanitation efficiency. The type of method selected should be based on considerations such as the type of food or beverage being processed and an operation’s individual sanitation system requirements. Some of the most commonly used rapid methods for environmental screening and monitoring of microbial contaminants on surfaces include:
ATP Bioluminescence. Bioluminescent methods in the form of luminometers and ATP swabs/ sponges, considered a “real-time” procedure because results are acquired in one to two minutes, are effective for use as tools to monitor the efficacy of sanitation. ATP bioluminescence technology reports results in relative light units (RLUs), which indicate the general level of organic residue or soil on a given surface. In general, ATP bioluminescence technology requires little to no time and labor for preparation, is easy to operate, and requires little training to use. There are a number of companies with ATP test systems for hygiene monitoring on the market that offer very rapid indicator readings in hand-held formats.
ATP is used following cleaning and sanitizing and prior to start-up to ensure that these activities were effective in removing soils from the equipment or facility surfaces. The application also allows efficacy of sanitation to be used as a critical control point in HACCP because results can be obtained quickly and easily. If a positive reading is revealed, the line can be recleaned before production begins. As a screening test, ATP provides instant gratification—it tells you if cleaning practices were effective in removing soils so the sanitation crew can take immediate corrective action to remove remaining residues, which left unchecked can form biofilms, especially on tanks, sanitary piping, pumps , hoppers, extruders, heat exchangers, and homogenizers from which they are difficult to remove once established.
However, ATP results do not tell you whether the surface is microbiologically acceptable, according to your in-house and regulatory standards. In other words, it does not tell you how many or what kind of microorganisms or chemical contaminants are present on the surface—only that there is organic matter present on the surface in which microorganisms can grow. And because most hygiene monitoring devices measure total ATP, which includes both microbial and the ATP present in the sample or food residue, ATP levels may vary depending on the composition of the microbial populations and their metabolic activity. Also, sanitizer residues on food contact surfaces or certain food components may interfere with the ATP reaction.
ATP is a support tool for your environmental testing program, and as such, you still want to periodically swab surfaces and conduct full microbiological analysis for specific organisms to confirm sanitary conditions.
There are also several swab alternatives to ATP that are available in the form of contact paddles, dip slides, sponges and contact plates that can provide near-immediate results to assess surface cleanliness which rapidly measure contamination on equipment, surfaces and in liquids on-site.
Surface Contact Plates. With surface contact plates, there is no time or labor required if the plates are pre-prepared. These provide fairly accurate results, although results should still be considered estimates since some microbial contaminants do not adhere to agar. These plates are easy to use, requiring little or no training unless the plates must be manually prepared, and are extremely consistent when purchased prepared.
Paddle Method. The paddle method is an innovative improvement on the conventional swab. The small paddle, containing bacteriological growth medium on both sides, is rubbed onto the surface, incubated for the appropriate time and temperature, and the colonies are enumerated. There is no time or labor required for preparation with this method, and it offers extremely consistent media preparation. The paddle also is easy to use, with no user training required.
Petrifilm Contact Method. 3M Petrifilm is very effective when used to verify sanitation at critical control points involving equipment and other environmental testing. Essentially, the Petrifilm plate can be used as a direct contact or swab contact method to detect microbial contaminants. It can also be used as an air sampling tool, increasing its versatility for use in a food plant environmental hygiene monitoring testing program.
Protein or Carbohydrate Analysis. With these test strip methods, the target surface is sampled and then the sample is exposed to chemicals to achieve detection of environmental surface contaminants in minutes. If proteins or carbohydrates are present, a color change occurs on the test strip. The color development is in relation to the concentration of protein or carbohydrate on the surface.
If ATP or a swab technique indicates that there are residual contaminants on surfaces post-cleaning and sanitizing, you may want to use a rapid microbiology test kit to identify what type of bacteria you are dealing with. These kits can be used in the production area and take only a few minutes to result. The rapidity and sensitivity of immunoassay-based test kits and systems have come a long way in the past few years due to developments in enzyme immunoassay, immunoprecipitation, lateral flow and immunomagnetic separation techniques.
The enzyme immunoassay (EIA) and the enzyme-linked immunosorbent assay (ELISA) are the most commonly used techniques for rapid detection of pathogen and toxins. ELISAs have been designed for the detection of specific pathogens, toxins and enterotoxins, antibiotics, drug and pesticide residues, and some are designed to detect specific organisms such as Salmonella enteriditis or Listeria monocytogenes from food or environmental samples. There are many types of immunoassay from which to choose, as well. The convenience of the portable, self-contained dipstick-style sampling systems have proved beneficial to plant operations; these devices have gone a long way toward the HACCP ideal of on-line or at-line monitoring.
The availability of advanced selective chromogenic differential plating media is another option for detecting specific pathogens in environmental samples. These easy-to-use plates can differentiate Listeria monocytogenes, for example, from other, non-pathogenic species of Listeria in as little as 24 hours. The good news is that the high specificity and sensitivity of these plating media enable the processor to quickly identify whether corrective action is warranted and/or determine the best measures to take against a particular pathogen, if detected.
If the plant has an in-house laboratory, the company might consider using an automated rapid instrument for specific detection of bacteria and toxins, such as Salmonella, Listeria, Staphylococcus aureus and E. coli O157:H7, as well as total aerobic counts. Many of these devices, based on optical or impedance techniques, are computerized, multitasking, multi-user systems that allow electronic data recording and handling. The environmental sample is typically transferred directly from the sampling device into an automated benchtop instrument. Results are typically simple to interpret (pass/fail mode) and these systems can analyze many times as many samples as conventional methods. They are extremely accurate, there is much less error than plate counting, and minimal training is required. Automated systems are designed to allow the analyst to test for multiple pathogens and spoilage organisms at the same time, and can be used to detect target microorganisms in a few hours.
Again, these rapid test kits and automated microbiology systems can assist the plant in determining whether there is likely Staphyloccocus aureus, Listeria monocytogenes or any number of pathogenic bacteria present if a problem is indicated by ATP or initial swab screening. If that quick screen indicates that there is a problem, then classical microbiological methods must be performed by the in-plant laboratory or by a third-party testing laboratory for confirmation.
Environmental hygiene monitoring should also include allergen testing, especially if you have shared equipment used for allergen and non-allergen containing items. Several allergen test kits are available and can be used in the same way as other environmental hygiene tests to obtain a rapid indication about whether allergenic residues are present on tested surfaces. First, it is important to validate the effectiveness of your cleaning practices (SSOPs), which can be done by sending production start-up samples to a third-party laboratory, such as FARRP at the University of Nebraska, to obtain analytical results on allergen residues. Having production start-up samples tested for the specific allergens you are concerned about will validate whether your SSOPs effectively removed allergenic residues from your equipment. Once sanitation practices have been independently validated, the processor can select test kits to specifically look for allergen-containing residues on a routine basis. Many of the available test kits can detect allergens down to a threshold that is less than what would force a recall.
Verifying the efficacy of cleaning and sanitizing efforts is an essential part of the food company’s environmental hygiene monitoring program. It is not enough to see that processing plant floors and walls look clean and that food-contact equipment shimmers prior to the day’s run. An effective environmental sampling and testing program is the only way to know that you’ve cleaned and sanitized the plant environment, equipment and product-contact surfaces to a microbiological and allergen-free level.
While there are places and surfaces in the plant that should always be monitored for cleanliness, such as high-risk drain areas and drain components, it is a good idea to periodically check out-of-the-ordinary places for trouble. If sanitation personnel and QC technicians concentrate solely on routine areas, you cannot be sure if there is contamination in areas or on surfaces where you didn’t expect it.
Brian Campbell is Director of Research and Development with Frozen Specialties, Inc. His 20 years of experience in R&D, food safety and quality assurance includes frozen foods, meats, bakery, dairy and low acid canning at such companies as Sara Lee, Land O’Lakes, Del Monte and Pillsbury.
Campbell is also a world-class and internationally recognized cribbage and ice fishing champion. He has promised to take Julie ice fishing in his home state of Minnesota. Watch for next spring’s article follow-up with instructions for the safe handling of fresh-caught fish!