Policy on Listeria monocytogenes in ready-to-eat foods (2023): Appendix C, Additional control measures

Use of food additives, food processing aids and post-packaging treatments for ready-to-eat foods

If present, it is possible for L. monocytogenes to transfer from the environment onto RTE foods that are exposed to the environment prior to packaging. RTE food formulations now exist that incorporate food additives or food processing aids to eliminate, or reduce numbers of, L. monocytogenes. Post-packaging treatments (also known as post-lethality treatments) can also be applied to reduce or eliminate L. monocytogenes in RTE foods. These can be used alone or together for a combined effect. It is important to note that independent of their efficacy, RTE foods should be manufactured under sanitary conditions. Furthermore, the use of such control measures may reduce the relative risk level of the food and could justify a reduced sampling frequency (CFIA, 2023).

1. Food additives

   Food additives are regulated under the Food and Drugs Act and associated Marketing Authorizations which incorporate by reference their corresponding Lists of Permitted Food Additives (lists) (Health Canada, 2017b). All food additives currently permitted for use in Canada are reported in 1 or more of the lists with conditions about the types of food they are permitted in or upon as well as the maximum level of use. Manufacturers interested in using a food additive that does not appear on 1 or more of the lists or for a purpose, a level or in a food that is not described on the lists are required to file a food additive submission in accordance with Section B.16.002 of the Food and Drug Regulations before it can be used in or upon foods sold in Canada (Health Canada, 2021b; Government of Canada, 2023d).

   The use of food additives is 1 of various control measures in the overall approach to minimize the risks associated with L. monocytogenes in RTE foods. Hence, RTE food manufacturers should validate that the specific use of a food additive is efficacious in the food under consideration, with consistent listericidal or listeriostatic effects (CAC, 2009a).

   Research is constantly ongoing to find effective food additives that can provide growth inhibition or reduction of L. monocytogenes in RTE foods throughout their shelf-lives. As such, in certain situations, food additives may be used for the purpose of changing the categorization of a Category 1 RTE food into a Category 2A or 2B RTE food (Health Canada, 2012a; 2012b). Should questions arise regarding food categorization, the RTE food 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.

2. Food processing aids

   Although not defined in the Food and Drug Regulations, a food processing aid is considered 'a substance that is used for a technical effect during food processing or manufacture but, unlike food additives, its use does not affect the intrinsic characteristics of the food and it results in no or negligible residues of the substance or its by-products in or on the finished food' (Health Canada, 2014b; 2022a). Their use could be viewed as an additional tool to decrease the levels of L. monocytogenes. Nonetheless, the application of food processing aids may not guarantee the complete elimination of L. monocytogenes, if present. Therefore, the growth of L. monocytogenes may occur afterwards, as food processing aids do not function to inhibit or reduce the growth of L. monocytogenes in RTE foods throughout their shelf-lives. Furthermore, the action of certain food processing aids may be very specific. A multi-faceted evaluation of the safety, suitability and efficacy of such control measures should therefore be considered.

3. Post-packaging treatments

   The use of a post-packaging treatment can also be part of an overall approach to minimize the risks associated with L. monocytogenes in RTE foods. That intervention step can reduce the levels or eliminate L. monocytogenes present on the surface of foods due to the introduction of L. monocytogenes onto RTE foods during post-processing, prior to packaging.

   The use of novel technologies for post-packaging treatments could be subjected to a comprehensive assessment by the Food Directorate, Health Canada according to the "Guidelines for the Safety Assessment of Novel Foods" (Health Canada, 2022b). For 'non-novel' post-packaging treatments, it is highly recommended that the microbiological safety and efficacy of these food processing techniques proposed by the food industry (for example, steam pasteurization, hot water treatment, radiant oven heating, infrared heating, high-pressure processing) be assessed by regulatory authorities.