Focus on Food Safety: New Listeria policy is more user-friendly for manufacturers, retains rigour

Health Canada has updated its “Policy on Listeria monocytogenes in Ready-to-Eat Foods.” The new policy replaces the 2011 version and will come into effect on October 1, 2023. The updated policy, while still technically rigorous, is more user friendly with increased decision-making tools and visual aids to help interpret the complexity.

Clear pathways for manufacturers

Determining the risk category of a food is one of the top issues in the Listeria policy. Some food products allow Listeria growth during their shelf life, known as Category 1 product. Others have factors such as pH, water activity, thermal processes, freezing processes, inclusion of antimicrobial ingredients or processing aids, or novel processes, which make Listeria far less likely to be within the product and able to grow. These are known as Category 2 products. The 2023 policy includes comprehensive decision-making tools for manufacturers to understand where their product falls in the risk categories of 1, 2A and 2B. Once you know the risk, you can determine the level of attention and frequency required on environmental and product monitoring.

Effective preventive control

The 2023 policy establishes good manufacturing practices as essential for effective Listeria control. Management commitment, and effective implementation of the overarching HACCP or preventive control program, create the environment that allows good safety systems to work. While the policy does not name it, commitment to food safety culture is essential for effective Listeria control, as workers must feel implicated and have organizational support for applying preventive controls and participating in monitoring programs.

Environmental monitoring

Listeria is notorious because it can thrive in biofilms in refrigerated environments. Environmental monitoring is the swabbing of surfaces for presence of Listeria or other organisms. It’s typically done during manufacturing, usually three hours after start of operations, as this is when Listeria would rub off into product from biofilms in machines. It is also done immediately after pre-operation sanitation to monitor effectiveness of sanitation protocols. When determining priority swabbing locations, individuals designing testing protocols need to take time inspecting equipment and processes to look for places where food accumulates inconspicuously and cracks or crevices that are hard to clean. Direct food contact surfaces are top priority, including machines, belts, and conveyors. Secondary priority is for non-contact points where Listeria thrives and quickly cross contaminates, such as hoses, drains, and mops. Sampling guidance has been created for high- and low-risk products and non-food contact surfaces.

Product testing

The 2023 policy has clear tables for quantity of samples required for product testing. The high-risk action criteria is any detection of Listeria monocytogenes in a single or composite 5 x 25 g sample. Low-risk action criteria is enumeration at greater than 100 cfu/g in a 5 x 10 g sample evaluated separately. High-risk products are more likely to be sampled frequently, thus the allowance for compositing to mitigate costs. However, compositing may not allow for precise detection and, if flagged for positive results, would require repeated testing.

Frequency and methods of testing

In the 2023 policy, testing frequency is determined by a systematic evaluation of the risk, including efficacy of the preventive control program, risk category of the product, historical in-plant data, and size of the manufacturing lot. Consulting a Canadian Food Inspection Agency (CFIA) inspector is essential in determining appropriate frequency. Analytical methods should be approved and listed in Health Canada’s Compendium of Analytical Methods.

Importance of process validation

Food manufacturers are required to validate their ingredient or process, using outcomes-based frameworks showing evidence that interventions are effective.

Trend analysis

In microbiological testing, it’s typical to see variation in samples. Statistical process control (SPC) allows for the tracking of trends over time, to visualize common cause and special cause variations. The new Listeria policy recommends, but does not indicate how to do, SPC. Organizations such as ASQ provide free educational tools for SPC. Control Charts and Pareto analysis are useful for prioritizing attention and observing loss of control.  

Dr. Amy Proulx is professor and academic program co-ordinator for the Culinary Innovation and Food Technology programs at Niagara College, Ont. She can be reached via email at aproulx@niagaracollege.ca.

This column was originally published in the June/July 2023 issue of Food in Canada.