Explore More Food Safety

The old axiom, “you can’t test quality into a product,” has often been attributed to W. Edwards Deming, noted statistician, professor and quality management expert. Deming emphasizes that quality must always be built into the process from the very beginning, rather than relying on testing to ensure quality.

Food safety, probably the most important aspect of food quality, works in the same way. You can use testing to know whether you have a food safety problem, but the best way to prevent a food safety catastrophe is by following good manufacturing practices (GMPs) and practicing HACCP and Preventive Controls (PCs) as required by governing agencies. Of course, this means conducting pathogen tests early and often so problems can be spotted before contaminated food gets out the door, potentially killing consumers and your business.

Boar’s Head, one of the most respected names in RTE lunch meats and cheeses, learned the hard way just how expensive a recall can be, ditching millions of pounds of liverwurst last year due to a Listeria monocytogenes (Lm) contamination — and closing a facility. The USDA’s FSIS provided a review of the Lm outbreak and causes for it, which are often the result of harborage in equipment or in building drains and supporting members.

But Boar’s Head wasn’t the only outbreak in 2024. According to a press release from Bill Marler, noted food safety attorney, the last quarter of 2024 was fraught with too many foodborne illness outbreaks. Some of these include:

• SunFed cucumber Salmonella outbreak
• Yu Shang Food Listeria outbreak
• Grimmway carrots E. coli outbreak
• Wolverine Packing E. coli outbreak
• Andre’s Catering E. coli outbreak
• McDonald’s E. coli outbreak
• Milo’s Poultry Farms egg Salmonella outbreak
• Boar’s Head Listeria outbreak — which involved millions of pounds — more than 7 million in an updated July 26, 2024 FSIS announcement — of deli meats and especially liverwurst.

Develop a Testing Strategy

“Savvy food processors have routine and robust food safety practices and testing programs to ensure the early detection of contaminants,” says Dr. Lorna De Leoz, Agilent Technologies global food segment director. “They understand that the cost of not testing is not worth the risk of losing hundreds of thousands of dollars due to endangering public safety, recalls, litigations and plant closures. In the case of the recent listeria outbreak at an American brand that specializes in premium deli meats, cheeses and other related products, the company had to close their manufacturing plant in Virginia, where the outbreak started. Product recalls is one thing, but companies could tarnish their reputation and shift consumer behavior away from their products — consumers could lose trust in the company or even the whole food category.”

Processors need to have an ongoing risk assessment program, says Jeremy Adler, technical service leader at Ecolab. “A risk assessment should guide decision-making concerning what to test for (and how to test for it). In accordance with Hazard Analysis and Critical Control Points (HACCP), this risk assessment should evaluate the entire production process, identify hazards that are inherent in your processes and products, and then develop targeted strategies for addressing those specific risks. Different products will produce different types of risk profiles. But something that unites all these various risk profiles is an emphasis on environmental monitoring for contamination that may arise as a result of specific contexts and processes.”

To further support early detection efforts, cleaning and sanitation teams can test for indicator organisms, which are generally non-pathogenic organisms that give a fuller sense of just how clean a system is, Adler says. For example, testing for all aerobic bacteria (i.e., all bacteria that survive under oxygen) can highlight trends that may indicate the first symptoms of a larger cleaning and sanitation issue.

Food processors decide which bacteria to test for based on a combination of risk assessment, regulatory requirements and the specific pathogens commonly associated with their products, De Leoz says. They analyze historical contamination data and consider the type of product and its processing conditions to identify likely pathogens. Compliance with regulations set by agencies like the U.S. FDA also guides their testing protocols. For example, processors often test for E. coli/STEC in raw meat products due to its severe health risks. In contrast, Listeria monocytogenes is tested in ready-to-eat products because it can grow at refrigeration temperatures. Salmonella is often tested in products like poultry, eggs and meat because it can cause outbreaks. By testing for multiple germs, processors can ensure their products are safe and reduce the risk of contamination in the supply chain. 

Set up an Environmental Monitoring Program

A robust environmental monitoring program (EMP) is essential in food manufacturing, says Tim Lombardo, senior director, EAS Consulting Group, a Certified Group Company. “Depending on the type of food produced, EMP tends to focus on pathogens such as Listeria and Salmonella, but other microorganisms may also be considered. The purpose of an EMP is to verify the effectiveness of other food safety programs, such as good manufacturing practices, sanitation, maintenance and traffic control. A positive pathogen finding in environmental sampling typically indicates a failure in one of these four programs. One of the goals of implementing an effective and robust EMP is to discover and address problematic areas far away from the product zone (i.e., floors and drains), well before the contamination reaches food processing surfaces.”

Determining the microorganisms of concern is based on the raw materials/ingredients, the type of food being manufactured, as well as the process, packaging and storage conditions, Lombardo adds. This determination is an integral part of the HACCP or Preventive Controls (PC) food safety plan development, referred to as the hazard analysis. This step is required of all USDA and FDA regulated food manufacturers. To assist in the hazard analysis, there are several guidance documents published by both USDA and FDA. There are also publications such as those provided by the International Commission of Microbiological Specifications for Foods and others. If, as a result of the hazard analysis, a pathogen or pathogens are reasonably likely to occur, they must then be included in the plan, mitigation strategies implemented to remove or reduce to a safe level and verification testing conducted.

Food processors’ testing programs benefit from a strong focus on EMPs, says Patrice Chablain, Hygiena chief scientific officer. This involves routine testing for indicator organisms, which can highlight potential contamination risks before pathogens proliferate. For example, Hygiena’s ATP testing solutions like UltraSnap with EnSURE Touch allow processors to assess cleanliness quickly and take corrective action immediately.

Processors should decide on target bacteria based on risk assessments, product profiles and historical data, Chablain adds. For instance, meat processors testing for E. coli/STEC may also test for Listeria monocytogenes and Salmonella, as these pathogens often thrive in similar processing environments. Prioritizing multiple targets ensures comprehensive coverage.

Testing Methods: Microbial is the “Gold Standard” but Requires a Day or Two

Shipping food products before confirming test results is risky as it can lead to public health dangers, costly recalls, legal issues, fines and damage to the brand’s reputation, says Agilent’s De Leoz. Food processors can use PCR and ELISA tests while waiting for microbial culture results. PCR is very sensitive and can detect low levels of bacterial DNA, making it suitable for processed foods. ELISA detects specific proteins and antigens quickly, helping with early decisions. Rapid detection kits, like lateral flow devices and colorimetric tests, are cost-effective and provide quick preliminary results. These kits are simple to use and give quick results. Although not as detailed as traditional microbial tests, these kits can still find specific germs or contaminants, allowing quick action. The cost savings and fast results make these kits valuable for food safety testing.

Rapid indicator testing, such as ATP testing, offers processors immediate insights into contamination risks, says Hygiena’s Chablain. For example:

• Use ATP testing to confirm cleanliness after sanitation.
• Employ rapid pathogen detection tools, like Hygiena’s InSite L. mono, for specific testing.
• Confirm positives with PCR tests such as the BAX System or foodproof, ensuring specificity and sensitivity.

These methods enable processors to release product confidently if rapid and ATP tests show no contamination, reducing reliance on lengthy culture reports.

EAS Consulting’s Lombardo takes a conservative — but safe — approach to test and hold. “Food processors must have a test-and-hold, or positive hold, approach for pathogenic testing. That is, when testing food or a food contact surface for a pathogen such as Listeria, Salmonella, and E. coli, the product is held pending shipment until the test results verify negative recovery. Indeed, not only should the product tested be held but the entire production on that line should also be held pending these test results, even though it may not have been sampled and tested. The reasoning being, if there is a positive recovery, there is not enough evidence at that time to determine whether the food processing equipment was the cause of the positive.”

While a positive hold should be required for all pathogen testing, the same is not necessarily true for indicator organisms like Enterobacteriaceae or spoilage organisms like yeast and mold, Lombardo adds. While a positive hold is still recommended for these microorganisms, they do not hold the same food safety implication as food pathogens.

“In-house rapid testing, while promising, does not provide the same accuracy and reliability as standard testing and should not be used in replacement of culture-based testing,” Lombardo says.

Dealing with Listeria monocytogenes is Especially Challenging

Lm has been known to close facilities because it can be so difficult to remove once it’s established a foothold. Preventing Listeria contamination hinges on rigorous cleaning to eliminate biofilm and thorough environmental testing, says Hygiena’s Chablain. Processors can use tools like Hygiena’s InSite L. mono, which combines swabbing with a built-in enrichment step for detecting Listeria monocytogenes and other species.

Key strategies include:

• Conducting routine ATP testing to validate cleaning efficacy
• Using environmental swabbing to detect harborage sites
• Mapping results to identify and address contamination hotspots

While identifying contamination sources is complex, processors must prioritize systematic cleaning and testing. Hygiena’s solutions provide actionable insights, ensuring facilities can stay operational while mitigating risks.

Closing a facility is certainly a last resort measure, Lombardo says. It is important to understand that once a pathogen has been found in product, there is likely a significant harborage point or several points. These harborage points are typically in hard-to-reach and hard-to-clean areas, often within food processing equipment or on its framework/supports in hidden places. Once a harborage point has been found, the contamination can be removed. Most of the time, this involves an engineering change in the equipment or its design. Changes to cleaning and maintenance procedures and schedules will also be needed to ensure the contamination does not return. Consultants and chemical suppliers can assist with both the investigation, identification of the harborage point as well as corrective and preventive measures.

Preventing Listeria contamination requires a proactive approach that combines rigorous sanitation protocols, regular testing and processing equipment — like pumps and valves —designed to minimize contamination risks, says Calle Danielsson, principal application engineer, Unibloc Hygienic Technologies. “An effective way to stay ahead of Listeria is through environmental swab testing, which helps processors verify their cleaning efforts and identify any problem areas where bacteria might still be hiding.”

Ultimately, a major reason Listeria becomes an issue is poorly designed equipment that creates harborage points — small crevices, rough surfaces or areas that are difficult to clean, Danielsson says. “If bacteria settle into these spots, they can be tough to eliminate. That’s why it’s critical to use equipment designed with cleanability in mind. At Unibloc Hygienic Technologies, we focus on hygienic pump designs that reduce the number of parts, eliminate hard-to-reach areas, and make disassembly and cleaning as easy as possible. Investing in the right equipment can help food processors maintain food safety and operational continuity.”

An important, yet often overlooked task is periodic disassembly of key equipment such as pumps and valves to allow for a more intensified cleaning and maintenance inspection, Lombardo says. Also, regular cleaning and sanitizing the undersides of hard-to-reach equipment such as pumps and pump stands, which are often installed just a few inches off the floor surface, is important. Not only is equipment a possible harborage point, but production room floors and drains should be checked for cracks, breaks, and floating tiles.

Food processors should use strong cleaning and sanitizing methods to manage and reduce the risk of Listeria contamination, says Agilent’s De Leoz. Regularly monitor surfaces, equipment and air, and focus on cleaning high-risk areas. Training employees on proper hygiene and installing hygiene stations to minimize contamination risks is also essential. This can’t be stressed enough: designing facilities with easy-to-clean surfaces, good drainage and regular maintenance of equipment will help to prevent contaminant buildup.

Rapid detection methods like PCR and ELISA can be used for quick results enabling immediate action if contamination is found, De Leoz adds. Food processors should conduct extensive environmental sampling throughout the facility if a product is contaminated with Listeria, especially in high-risk areas like cold storage and processing lines. They should then review and assess the effectiveness of current cleaning and sanitation protocols, including checking for biofilms.

If microbiological testing uncovers contamination, cleaning and sanitation teams need to implement a clear and comprehensive escalation process, says Craig Ledbetter, area technical support coordinator at Ecolab. This should include intensified testing to locate the source of the contamination (i.e., the root cause) and intensified sanitation in contaminated areas (for example, cleaning an entire piece of equipment, not just the component that tested positive for Lm).

This indicates another important point, Ledbetter adds. Cleaning and sanitization chemicals are only effective when correctly applied. Cleaning and sanitation teams need to examine the strengths and limitations of their procedures and chemical resources. They should have procedures with chemicals that are validated to clean and sanitize the specific piece of equipment and verify that the procedures are effective as applied on a routine basis. High-risk and difficult-to-clean areas must be treated rigorously, which may entail procedural changes beyond applying more and/or different chemical solutions.