Policy on Listeria monocytogenes in ready-to-eat foods (2023): Control measures

Control measures to meet the Table 1 microbiological criteria for L. monocytogenes in ready-to-eat foods

Control of ready-to-eat food manufacturing

RTE food manufacturers should have effective GMPs in place and be able to demonstrate that their food safety system controls L. monocytogenes in RTE foods in order to meet the microbiological criteria specified in Table 1. As incoming raw ingredients may contain L. monocytogenes, RTE food manufacturers should consider developing supply-chain controls on raw ingredients (for example, a formal agreement with the suppliers, Certificate of Analysis, GAP certification), and applying validated processing steps that would eliminate or reduce numbers of L. monocytogenes.

RTE food manufacturers should be aware that the following factors influence the potential for the introduction of L. monocytogenes in the post-process areas where foods are exposed to the environment prior to packaging (CAC, 2009a):

infrastructure
plant layout (for example, traffic control, separation of equipment and utensils between raw and RTE areas)
equipment design and maintenance (for example, equipment that require disassembly, such as slicing equipment)
effectiveness of sanitation practices
employee training and practices

This is managed through the implementation of GMPs, including adequate sanitation practices. Rigorous adherence to GMPs is essential due to the potential presence of Listeria spp. in the environment, with their ability to spread and thrive in the processing environment (Farber et al., 2021). As such, a multi-facetted approach should be used to prevent persistence of Listeria spp. via the physical disruption of biofilms and application of sanitizers which may need to be rotated, as applicable (Spanu and Jordan, 2020; Mazaheri et al., 2021). In addition, sanitation management can lead to innovations and sanitary design improvement (for example, equipment, facility).

Several scientific publications are available on how to minimize the presence of Listeria in RTE food manufacturing environments (Tompkin et al., 1999; Zoellner et al., 2019; Spanu and Jordan, 2020). In addition, workshops and documents developed by food industry trade associations on current best practices for the control of L. monocytogenes in RTE foods and the implementation of environmental monitoring programs within specific segments of the industry are also accessible. These resources may represent good supplementary information for RTE food manufacturers.

Furthermore, RTE food manufacturers should conduct on-site observation to assess adherence to GMPs that can influence the presence of Listeria spp. in the food processing environment (CAC, 2009a). Keeping in mind that the presence of Listeria spp. is an indicator of the potential presence of L. monocytogenes, it is not possible to predict, by visual observation alone, the degree to which Listeria spp. may occur in areas where RTE foods are exposed both before and during final packaging. An effective environmental monitoring program, supported by investigative sampling to detect sources of Listeria spp., should be used to identify additional steps the manufacturer should take to continuously improve its food safety system. Experience indicates that environmental sampling is the most sensitive tool to verify the effectiveness of control measures to prevent the introduction of L. monocytogenes into RTE foods (Tompkin et al., 1992; Tompkin, 2002; Farber et al., 2021).

Process control

Increased knowledge of the ecology of L. monocytogenes in RTE foods has clarified the categories of foods in which the growth of L. monocytogenes can or will not occur. Some RTE food manufacturers may also use food additives to control L. monocytogenes throughout the shelf-life of a food (see Appendix C). Although food additives have a long history of use against foodborne pathogens by limiting their growth or by reducing their numbers, manufacturers should confirm that the specific use of a food additive is permitted in Canada and validate its efficacy in the food under consideration. Furthermore, food processing aids and post-packaging treatments can also be used to eliminate or reduce numbers of L. monocytogenes in RTE foods (see Appendix C).

Environmental sampling (Figures 2, 3 and 4) and testing

Steps should be taken to reduce the potential for the introduction of L. monocytogenes into RTE foods by addressing Listeria spp. in the food processing environment. It is important that RTE food manufacturers are able to demonstrate that their food safety system will prevent L. monocytogenes from establishing itself in their manufacturing facilities by performing environmental sampling and testing. Risk-based frequency details are left to the discretion of the relevant regulatory authority (CFIA, 2023). The presence of Listeria spp. in a RTE food plant indicates that GMPs may be inadequate, as it suggests the potential presence of L. monocytogenes in the environment or the food. Any observation of the inadequate implementation of GMPs that could lead to the introduction of L. monocytogenes into a RTE food should trigger a review of the manufacturer's process and procedures. This review should also take into account environmental and end-product test results.

If Listeria spp. are found in the environment, RTE food manufacturers should conduct investigative sampling to determine their origin, following Figures 2 to 4, below. Investigative sampling differs from the routine environmental sampling used to monitor the control of Listeria spp. It involves collecting additional samples from different sites to help identify more clearly the potential sources of Listeria spp. Investigative sampling is an indispensable approach for identifying and eliminating harbourage sites (Tompkin, 2002; CAC, 2009a). RTE food manufacturers should identify and eliminate potential sources of Listeria spp. (for example, root cause analysis) by performing process review, environmental sampling and end-product testing. Furthermore, if the review indicates that Listeria spp. are not being controlled (for example, processing conditions that cannot eliminate Listeria spp. in the raw materials, an inadequate food safety system that cannot eliminate Listeria spp. from the post-process environment), this should be taken as evidence for the need to improve control measures. RTE food manufacturers should respond, in a timely manner, to all positive environmental test results, with appropriate corrective actions.

The expected steps to be undertaken by RTE food manufacturers when sampling both food contact surfaces (FCSs), that is, any surface or object that comes into contact with RTE foods, and non-FCSs, that is, any surface or object that does not come into contact with RTE foods, and testing for Listeria spp., are outlined in this section. The steps indicated in Figures 2 to 4 represent the minimum sampling and testing recommended by Health Canada. Manufacturers can exceed these minimum recommendations. Health Canada's Compendium of Analytical Methods lists methods that have been accepted for use in the administration of the Food and Drugs Act and Regulations (Health Canada, 2021a). Details on environmental sampling are described in method MFLP-41 (Health Canada, 2010). Methods and laboratory procedures for the analytical testing of environmental samples for Listeria spp. can also be found in the compendium. Industry should confirm that the 'application' section of the method is appropriate for the intended purpose.

It is important to perform environmental sampling in post-process areas where foods are exposed to the environment prior to packaging since positive results could be indicative of the potential presence of L. monocytogenes. Verifying that the processing environment is free from Listeria spp. (that is, reduced to below detectable levels) is the key to producing safe RTE foods.

A risk-based approach should be used in designing an environmental monitoring program. The environment of the following foods should be monitored and sampled at greater frequencies:

food that is specifically produced for consumption by vulnerable populations
food in which the growth of L. monocytogenes to levels exceeding 100 CFU/g can occur throughout the stated shelf-life
food that does not contain L. monocytogenes inhibitors
food that is not subjected to a post-packaging treatment before distribution

The specifics of an environmental sampling plan should be determined based on the probability that finding a Listeria spp. positive site could be indicative of the introduction of L. monocytogenes into RTE foods. One approach to consider such probability is by dividing the plant into different zones (ICMSF, 2018a; Simmons and Wiedmann, 2018; Spanu and Jordan, 2020). With the zone concept, Zone 1 would represent the highest probability for the introduction of L. monocytogenes into RTE foods and Zone 4 would represent the lowest probability for the introduction of L. monocytogenes into RTE foods. Zone 1 would include FCSs where RTE foods are exposed to the environment prior to packaging. Zone 2 would include non-FCSs in proximity to Zone 1 (for example, control panels adjacent to FCSs). Zone 3 would be further from the packaging area, but within the processing area (for example, floor drains, walls). Zone 4 would be located outside the processing and packaging areas (for example, outside of the area where RTE foods are exposed, such as loading docks, locker rooms and cafeterias). It would be expected that more environmental samples be taken from Zones 1 and 2, while Zones 3 and 4 may be sampled at a lower frequency.

The environmental monitoring program should be sufficiently robust regarding sampling selection, frequency of sampling, number of samples, method of sampling and so on to enable both RTE food manufacturers and the relevant regulatory authority to conclude, when reviewing data, that the foods being produced are safe (CAC, 2009a; CAC, 2020).

Food contact surfaces

Each RTE food manufacturer should have an environmental monitoring program that has been designed to assess the effectiveness of control measures, including sanitation and other GMPs, as well as the potential for the introduction of L. monocytogenes into RTE foods. Environmental monitoring programs should include routine sampling of FCSs that come into contact with exposed RTE foods prior to packaging. Such samples should be collected during production, typically after 3 hours of operation. The use of sponges or swabs to sample the surface areas of equipment is recommended. Examples of FCSs include: chill brines, containers, racks for transportation, conveyor belts, slicers, dicers, shredders, blenders, tables and equipment used to assemble/package foods, packaging equipment, hand tools, gloves, aprons, metal surfaces with gaps (for example, bad welding), food residue sites and other hard to clean areas (Health Canada, 2010).

Furthermore, additional sampling may be conducted immediately before start-up, to verify the effectiveness of sanitation. As part of their verification activities, RTE food manufacturers may find testing for adenosine triphosphate (ATP) bioluminescence or aerobic colony/plate count (ACC or APC) to be useful for this purpose. However, these methods cannot be used to replace testing for Listeria spp.

The number of sites (for example, 1 to 10) tested will vary according to the complexity of the processing system and packaging line. The frequency and points for routine sampling should be plant and line-specific, based on the manufacturing processes and control measures present (Tompkin et al., 1992; Zoellner et al., 2018). Samples should also be collected from non-FCSs as an additional measure of monitoring and verification. An increase in sampling sites (FCSs and non-FCSs), as well as the frequency of sampling, should be considered both during and after special circumstances (for example, construction, the installation or modification of equipment, overhead/ceiling leaks in exposed food areas), since these activities may lead to a loss of L. monocytogenes control in the food processing area (Tompkin, 2002; Spanu and Jordan, 2020). RTE food manufacturers should consider seeking expert technical advice to customize the best approach for their environmental sampling.

One of the goals of the Listeria policy is to encourage RTE food manufacturers to perform robust environmental sampling on a regular basis and to perform trend analysis on their results to detect problems that need corrective actions. Figures 2 and 3 below are reflective of the risk the RTE food may pose to consumers if L. monocytogenes is present. RTE food manufacturers should respond as soon as possible to all positive FCS test results, with appropriate follow-up actions, including corrective actions (see the section on Corrective actions for positive test results of food contact surfaces and non-food contact surfaces, below) and investigative sampling (as per Figures 2 and 3). These actions should take into account the type and location of the sampling sites, as well as the category of food. At a minimum, the FCSs in the routine monitoring program should be included when re-sampling. In some situations, food in various stages of processing or product build-up can be used as additional FCS samples to further assess the presence of Listeria spp. along a production line or system. Furthermore, if FCS samples are found positive at 2 (Figure 2) or more (Figure 3) steps, end-product testing should be performed.

Testing for Listeria spp. and reacting to positive results as if they were L. monocytogenes provides for a more sensitive and broader environmental monitoring program than would testing for L. monocytogenes alone (Farber et al., 2021). Nevertheless, if manufacturers choose to test FCSs for L. monocytogenes instead of Listeria spp., it is recommended that individual lots of food produced at the time of FCS sampling be held pending results from this testing. End-product testing for L. monocytogenes should be performed if L. monocytogenes is detected on a FCS (Figures 2 and 3, below).

Persistence of Listeria spp. on food contact surfaces

In a situation where 2 or more FCS samples from the same production line (that is, using the same equipment) are found positive for Listeria spp. within a short timeframe, such a situation is considered to be potential evidence of persistence and an indication that the food safety system (for example, GMPs, sanitation practices) may be inadequate to prevent the establishment of Listeria spp. in the food processing environment. This short timeframe is operation-specific. It will vary based on factors such as production volume, production seasonality and testing frequency.

RTE food manufacturers should respond as soon as possible with appropriate follow-up actions, including corrective actions (see the section on Corrective actions for positive test results of food contact surfaces and non-food contact surfaces, below) and investigative sampling. Investigative sampling will assist in finding and eliminating the source of Listeria spp., particularly if there is a harbourage site from which Listeria spp. or a specific subtype of L. monocytogenes is repeatedly isolated (CAC, 2009a). These actions should take into account the type and location of the sampling sites, as well as the category of food. This information should be communicated as soon as possible to the relevant regulatory authority.

Non-food contact surfaces

Environmental monitoring programs should also include routine sampling of non-FCSs. Examples of non-FCSs include: drains, standing water, cracks in floors and walls, smokehouses, floors in heavily-trafficked areas, tires on fork-lift trucks, foot and wheel baths that are in poor condition, high-pressure hoses, cleaning tools (mops, squeegees, brushes and so on), trash cans, under-side of conveyor belts, hollow rollers, roller guards, bearings, chill tanks, refrigerators, cold rooms, ice makers, overhead pipes, drip pans, wet insulation, maintenance tools, dust from construction and air filtration equipment (Health Canada, 2010).

It is important to perform follow-up actions (including corrective actions, see the section below) when non-FCSs test positive for Listeria spp. (Figure 4, below). In general, detection of Listeria spp. from non-FCSs, including L. monocytogenes, usually precedes their detection from FCSs (Tompkin et al., 1999; D'Amico and Donnelly, 2008). Accordingly, identifying sources of Listeria spp. away from the production line and preventing their transfer within the food processing environment is a fundamental principle of Listeria control. It should be noted that the sampling sites selected after the completion of corrective actions may differ from those assessed during routine monitoring. Upon re-sampling, the original or nearby sites might be negative, but other sites might reveal a positive, and hence be informative in resolving the problem. Positive test results collected over time can also be used to determine a trend. A review of data from trend analysis would indicate whether the RTE food manufacturer is properly controlling Listeria (see the section on Importance of trend analysis, below).

Corrective actions for positive test results of food contact surfaces and non-food contact surfaces

RTE food manufacturers should respond as soon as possible to all positive FCS and non-FCS test results for Listeria spp. (Figures 2 to 4, below) with appropriate corrective actions. These may include the following:

increasing or correcting sanitation procedures
- intensified cleaning and sanitizing beyond FCSs, including equipment disassembly
- verification of cleaning and sanitizing procedures
- intense cleaning and sanitizing of the surrounding areas
- modification of equipment for improved cleanability
performing additional sampling (Figures 2 to 4)
- timely re-testing of the positive sites
- testing of RTE foods that were potentially in contact with positive FCSs
obtaining additional data to confirm hypotheses when conducting root cause analysis
developing and implementing an investigative sampling plan (for the affected line and possibly the food)
in-depth review of the RTE food manufacturer's food safety system (for example, HACCP plan) and making necessary changes to reduce the potential for the introduction of L. monocytogenes in the post-process areas where foods are exposed to the environment prior to packaging (see the section on Control of ready-to-eat food manufacturing, above)

Corrective actions should be monitored to confirm their effectiveness. All of this information should be documented and integrated into the RTE food manufacturer's trend analysis (see the section on Importance of trend analysis, below).

RTE food manufacturers should attempt to determine the potential sources of Listeria spp. by means of process review, environmental sampling (including investigative sampling) and end-product testing.

Sampling flowchart for food contact surfaces, Category 1 foods and Category 2 foods for vulnerable populations. Text version below. — **Figure 2: Sampling guidelines for food contact surfaces, Category 1 ready-to-eat foods and Category 2 ready-to-eat foods specifically produced for consumption by vulnerable populations**

Sampling flowchart for food contact surfaces and Category 2 foods for the general population. Text version below. — **Figure 3: Sampling guidelines for food contact surfaces and Category 2 ready-to-eat foods produced for consumption by the general population**

Sampling flowchart for non-food contact surfaces. Text version below. — **Figure 4: Sampling guidelines for non-food contact surfaces, especially those in proximity to food contact surfaces**

Sampling and testing of ready-to-eat foods (Table 1)

When manufacturing RTE foods, rigorous adherence to GMPs (with a focus on adequate sanitation) coupled with environmental monitoring (that is, implementation of an appropriate environmental sampling plan; Figures 2 to 4, above) is the most desirable approach to control Listeria in the food processing environment. Relying on the results of environmental testing will allow for better decision-making regarding the release of RTE foods, rather than relying solely on end-product testing. Accordingly, microbiological testing of food that results in no detection of L. monocytogenes may not portray the true overall microbiological condition of the food, as in general, testing gives only very limited information on the safety status of a food. This is due to, among other things, the non-uniform distribution of bacteria, such as L. monocytogenes, within a food (ICMSF, 2018b).

Nonetheless, end-product testing can be informative and is conducted for many different reasons, for example:

as part of the Listeria environmental monitoring program (for example, evaluation of end-product when FCSs test positive for Listeria spp., as stipulated in Figures 2 and 3, above)
periodic testing to verify the process or the effectiveness of control measures to prevent the introduction of L. monocytogenes into RTE foods
verification of the effectiveness of food additives or food processing aids
performing trend analysis
regulatory compliance
customer requirements
foreign country requirements
testing of foods sampled at various points in distribution, including retail, as part of surveillance or food safety investigation activities (for example, testing of previously distributed lots where continued exposure is expected)

Moreover, end-product testing for L. monocytogenes should be performed if L. monocytogenes is detected on a FCS (see the section on Environmental sampling and testing; Figures 2 and 3, above).

When testing RTE foods, food businesses should develop and implement:

written procedures for end-product testing with details on any hold and test procedures
sampling procedures
specifics of sampling frequency and size
methodologies to be used for testing (details regarding methodological approaches are left to the discretion of the relevant regulatory authority (CFIA, 2023))
follow-up actions

It is recommended that individual lots of food being tested be held pending results from testing, as specified in Table 1, below. Any test results for L. monocytogenes in a RTE food, at levels exceeding those specified in Table 1, should be addressed immediately by the food business. It is strongly recommended that food businesses communicate this information as soon as possible to the relevant regulatory authority having jurisdiction over risk management actions.

Samples of RTE foods submitted for the testing of L. monocytogenes should consist of 5 sample units of at least 100 g or mL each (Table 1, below), taken at random, and should be representative of the lot and the production conditions. In the case where individual lots cannot be differentiated by clear product markings or if the food business is unable to provide information that would allow for the differentiation of individual lots, then the entire day's production or the whole shipment would be considered as a single lot.

Ready-to-eat foods specifically produced for consumption by vulnerable populations

Irrespective of category, a qualitative method for L. monocytogenes (that is, a detection method using enrichment) should be used for end-product testing of RTE foods specifically produced for consumption by vulnerable populations. Recognized methods, such as MFHPB-30 (Pagotto et al., 2011a), can be found in the Compendium of Analytical Methods (Health Canada, 2021a). Industry should confirm that the 'application' section of the method is appropriate for the intended purpose. An analytical sample size of 5 × 25 g for these RTE foods should be used and analyzed separately or as a composite, as specified in Table 1, below.

When L. monocytogenes is detected in RTE foods specifically produced for consumption by vulnerable populations, the food business should start an investigation to determine whether potentially unsafe food has left its control and if so, the extent of distribution (for example, retail level, consumer level). It is also important to try to determine the source of L. monocytogenes, where its introduction has occurred and the lots involved. Investigative sampling will assist in finding and eliminating the source of Listeria spp., particularly if there is a harbourage site (Figure 2, above; CAC, 2009a). The food business should take action on identified unsafe lots of food. The investigation may reveal that previous or subsequent lots produced under the same conditions may be impacted and may represent a health concern. In such situations, risk management actions may be needed. More specifically, the detection of L. monocytogenes in these RTE foods should trigger immediate follow-up by the food business as described in steps B and C of Figure 2. It is strongly recommended that food businesses communicate this information as soon as possible to the relevant regulatory authority having jurisdiction over risk management actions.

Category 1 ready-to-eat foods

A qualitative method for L. monocytogenes (that is, a detection method using enrichment) should be used for end-product testing of Category 1 RTE foods. Recognized methods, such as MFHPB-30 (Pagotto et al., 2011a), can be found in the Compendium of Analytical Methods (Health Canada, 2021a). Industry should confirm that the 'application' section of the method is appropriate for the intended purpose. An analytical sample size of 5 × 25 g for these RTE foods should be used and analyzed separately or as a composite, as specified in Table 1, below.

When L. monocytogenes is detected in a Category 1 RTE food, the food business should start an investigation to determine whether potentially unsafe food has left its control and if so, the extent of distribution (for example, retail level, consumer level). It is also important to determine the source of L. monocytogenes, where its introduction has occurred and the lots involved. Investigative sampling will assist in finding and eliminating the source of Listeria spp., particularly if there is a harbourage site (Figure 2, above; CAC, 2009a). The food business should take action on identified unsafe lots of food. The investigation may reveal that previous or subsequent lots produced under the same conditions may be impacted and may represent a health concern. In such situations, risk management actions may be needed. More specifically, the detection of L. monocytogenes in these RTE foods should trigger immediate follow-up by the food business as described in steps B and C of Figure 2. It is strongly recommended that food businesses communicate this information as soon as possible to the relevant regulatory authority having jurisdiction over risk management actions.

Category 2 (2A and 2B) ready-to-eat foods

A quantitative method for L. monocytogenes (that is, an enumerative method done by direct plating onto selective agar) should be used for end-product testing of Category 2 RTE foods. Recognized methods, such as MFLP-74 (Pagotto et al., 2011b), can be found in the Compendium of Analytical Methods (Health Canada, 2021a). Industry should confirm that the 'application' section of the method is appropriate for the intended purpose. An analytical sample size of 5 × 10 g for this specific category of RTE food should be used and each analytical unit should be analyzed separately, as specified in Table 1, below.

When levels of L. monocytogenes exceed 100 CFU/g in a Category 2 RTE food, the food business should start an investigation to determine whether potentially unsafe food has left its control and if so, the extent of distribution (for example, retail level, consumer level). It is also important to try to determine the source of L. monocytogenes, where its introduction has occurred and the lots involved. Investigative sampling will assist in finding and eliminating the source of Listeria spp., particularly if there is a harbourage site (Figure 3, above; CAC, 2009a). The food business should take action on identified unsafe lots of food. The investigation may reveal that previous or subsequent lots produced under the same conditions may be impacted and may represent a health concern. In such situations, risk management actions may be needed.

More specifically, regardless of the L. monocytogenes levels in a Category 2 RTE food, immediate follow-up should be triggered by the food business as described in steps C and D of Figure 3, as well as in the section on Follow-up actions to positive ready-to-eat food test results, below. It is strongly recommended that food businesses communicate this information as soon as possible to the relevant regulatory authority having jurisdiction over risk management actions. The presence of L. monocytogenes at levels between 5 and 100 CFU/g in a Category 2 RTE food, occurring repeatedly at brief intervals, is likely an indication of an inadequate food safety system unable to control L. monocytogenes.

Follow-up actions to positive ready-to-eat food test results

Any RTE food that yields a positive test result for L. monocytogenes must lead to corrective actions by the food business, such as:

recalling food (that is, removing implicated foods from further sale or use, at any point in the supply chain)
initiating investigative sampling
initiating additional end-product testing
initiating a review of the food safety system

**Table 1: Sampling methodologies and microbiological criteria for *Listeria monocytogenes* in ready-to-eat^{Footnote a}foods**
Ready-to-eat (RTE) food category (intended consumers)	Sampling	Analysis	End-product testing	Action level for L. monocytogenes	Level of concern	Level of priority^{Footnote b}
Any category (vulnerable populations) RTE foods specifically produced for consumption by vulnerable populations, irrespective of RTE food category Category 1 (general population) RTE foods in which the growth of L. monocytogenes can occur^{Footnote c} throughout the stated shelf-life (for example,^{Footnote d} deli-meats, soft cheeses, hot dogs, meat spreads)	5 sample units (min 100 g or ml each), which are representative of the lot and the production conditions, taken aseptically at random from each lot	5 × 25 g analytical units,^{Footnote e} analyzed either separately or com-posited	Detec-tion	Detected in 125 g^{Footnote f}, ^{Footnote g}	Health Risk 1^{Footnote h}	High
Category 2A (general population) RTE foods in which a limited potential for growth of L. monocytogenes to levels not exceeding 100 CFU/g can occur^{Footnote c} throughout the stated shelf-life. A number of factors will be taken into consideration with regards to which foods may fall into this Category, that is, (1) RTE foods which are known to occasionally contain low levels of L. monocytogenes and their processing does not involve any heat treatment (based on validation); (2) RTE refrigerated foods with a stated shelf-life of 5 days or less. Such foods could include fresh-cut fruits and vegetables. Category 2B (general population) RTE foods in which the growth of L. monocytogenes will not occur^{Footnote l} (that is, increase not exceeding 0.5 log CFU/g) throughout the stated shelf-life (based on validation, as applicable). Such foods could include ice cream, hard cheese and frozen fruits.	5 sample units (min 100 g or ml each), which are representative of the lot and the production conditions, taken aseptically at random from each lot	5 × 10 g analytical units,^{Footnote e} analyzed separately	Enumer-ation	> 100 CFU/g^{Footnote i}, ^{Footnote j}	Health Risk 2^{Footnote h}, ^{Footnote k}	Medium to low
Note: If insufficient, inadequate or no information exists regarding the Category 2A or 2B categorization of the RTE food, it will be considered as a Category 1 RTE food. As such, the sampling and testing methodologies for Category 1 RTE foods, as specified in Table 1, should be used. Should questions arise regarding food categorization, the RTE manufacturer should be able to demonstrate in which category the RTE food falls. In cases where validation was conducted for categorization, the manufacturer should have documentation of adequate validation studies substantiating that L. monocytogenes cannot grow or that the RTE food will only support limited growth of L. monocytogenes to ≤ 100 CFU/g throughout the stated shelf-life. Footnote 1 For a definition of RTE foods, see the section on Application of the policy. Return to footnote a referrer Footnote 2 Other criteria (for example, process, packaging, trend analysis, outbreak data) could also have an impact on the level of priority for the frequency of process monitoring, environmental sampling and end-product testing. Risk-based frequency details are left to the discretion of the relevant regulatory authority (CFIA, 2023). Return to footnote b referrer Footnote 3 For additional details on determining the RTE food category, see Figure 1 and the section on Demonstrating the ready-to-eat food category. Return to footnote c referrer Footnote 4 These are traditional examples of Category 1 RTE foods. Return to footnote d referrer Footnote 5 The analytical unit is taken from each sample unit. Return to footnote e referrer Footnote 6 A qualitative method for L. monocytogenes (that is, a detection method using enrichment) should be used for end-product testing of such RTE foods. Recognized methods, such as MFHPB-30 (Pagotto et al., 2011a), can be found in the Compendium of Analytical Methods (Health Canada, 2021a). Industry should confirm that the 'application' section of the method is appropriate for the intended purpose. For additional details, see the sections on Ready-to-eat foods for vulnerable populations and Category 1 ready-to-eat foods, above. Return to footnote f referrer Footnote 7 Assuming a log normal distribution, this sampling plan would provide 95% confidence that a lot of food containing a geometric mean concentration of 0.023 CFU/g and an analytical standard deviation of 0.25 log CFU/g would be detected and rejected if any of the 5 samples are positive for L. monocytogenes (CAC, 2009a). Return to footnote g referrer Footnote 8 For a definition of health risk levels, see Appendix A. Return to footnote h referrer Footnote 9 A quantitative method for L. monocytogenes (that is, an enumerative method done by direct plating onto selective agar) should be used for end-product testing of such RTE foods. Recognized methods, such as MFLP-74 (Pagotto et al., 2011b), can be found in the Compendium of Analytical Methods (Health Canada, 2021a). This will determine the concentration of L. monocytogenes (CFU/g) in the food. Industry should confirm that the 'application' section of the method is appropriate for the intended purpose. For additional details, see the section on Category 2 (2A and 2B) ready-to-eat foods, above. Return to footnote i referrer Footnote 10 Assuming a log normal distribution, this sampling plan would provide 95% confidence that a lot of food containing a geometric mean concentration of 93.3 CFU/g and an analytical standard deviation of 0.25 log CFU/g would be detected and rejected based on any of the 5 samples exceeding 100 CFU/g L. monocytogenes (CAC, 2009a). Return to footnote j referrer Footnote 11 Levels of L. monocytogenes exceeding 100 CFU/g in a Category 2 RTE food, in any 1 of the analytical units will, at a minimum, trigger a Health Risk 2 concern. Return to footnote k referrer Footnote 12 For additional details on determining the RTE food category, see Figure 1 and the section on Category 2B ready-to-eat foods. A RTE food in which the growth of L. monocytogenes will not occur (CAC, 2009a) includes the following: pH < 4.4, regardless of a_w a_w< 0.92, regardless of pH combination of factors (for example, pH < 5.0 and a_w< 0.94) frozen foods (that is, labelled 'Keep Frozen' on the package) In the specific context of end-product testing for L. monocytogenes, the pH and a_w should be determined for at least 3 out of the 5 analytical units. Recognized methods for measuring pH and a_w, such as MFHPB-03 (pH) and MFLP-66 (a_w), can be found in the Compendium of Analytical Methods (Health Canada, 2021a). Industry should confirm that the 'application' section of the method is appropriate for the intended purpose. The growth of L. monocytogenes is presumed to occur if any 1 of the analytical units falls outside the range of pH and a_w values in which the growth of L. monocytogenes will not occur (as above). Return to footnote l referrer

Importance of trend analysis

As previously stated, RTE food manufacturers should not rely solely on end-product testing to verify their control measures for L. monocytogenes. The manufacturer's food safety system should use modern quality control and statistical methods to monitor the process and the effectiveness of control measures. This will allow for the detection of spatial-temporal patterns suggestive of sources of L. monocytogenes, particularly harbourage sites that may then be further investigated and eliminated (Zoellner et al., 2018). Data obtained from trend analysis can be modelled and used to verify control measures, as well as to assess environmental monitoring activities and to better target compliance activities. It is important to note that negative results, if due to an inappropriate sampling methodology, can lead to a false sense of safety. Positive findings should be viewed as the successful identification of an issue that should lead to follow-up actions, including corrective actions (Spanu and Jordan, 2020). Where possible, quality control and statistical methods should include modern graphical techniques (for example, control charts, Pareto diagrams). All data should be made available to individuals responsible for managing and overseeing the implementation and verification of control measures for L. monocytogenes. Responsibility for updating and disseminating the data should be assigned to 1 or more individuals within the organization (for example, quality assurance, food safety or HACCP coordinators).

On going review and analysis of the data for Listeria spp. collected during routine monitoring, as well as from investigative sampling, should be performed to detect trends prior to the development of major issues. Such reviews should also provide information on the prevalence of Listeria spp. and its fluctuation over time. They also serve to identify issues that should be addressed in a timely manner. Attention should be given to the dates and locations of positive samples to determine whether low-level or sporadic positive samples occur at particular locations that may have gone previously unnoticed (CAC, 2009a). The use of the zone concept for environmental monitoring can be useful for early detection of Listeria spp. on non-FCSs to help prevent their transfer to FCSs (see the section on Environmental sampling and testing, above). In situations where there is evidence of persistence (see the section on Persistence of Listeria spp. on food contact surfaces, above), molecular characterization techniques such as whole-genome sequencing may help during root cause analysis to identify harbourage sites (persistence) or transient Listeria spp. in the food processing environment. As more information becomes available from trend analysis, it should be used to achieve improved control of Listeria as the RTE food manufacturer gains experience and makes necessary adjustments to its food safety system.

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Date modified:: 2023-03-27

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