Food processors must follow an integrated approach in order to prevent proliferation of listeria in the final product. Control of L. monocytogenes is required at all stages in the food chain.
The consumption of contaminated food is the main route of transmission of listeriosis, however because listeriosis cases are sporadic it is particularly difficult to detect links between human cases and causative foods. It is estimated that levels of L. monocytogenes below 100cfu/g of food represent a very low risk of listeriosis for all population groups.
Persistence in food processing environments is considered to be the major source of ready-to-eat ( RTE) food contamination. Persistence appears to be the result of (1) improper hygiene conditions and (2) high adaptive ability of listeria against physical–chemical factors, for example, biofilm-forming capacity.
There are a number of contamination routes whereby L. monocytogenes can enter the food chain (Fig 1).
In addition: It is essential to conduct environmental monitoring to identify areas where L. monocytogenes proliferates.
Role of indicator testing:
Testing in the environment and or finished product indicates that sanitation and zoning controls are working and that the environment is clean. Does not replace pathogen monitoring, it provides additional information. Verifying that a processing environment is under control requires independent testing for Listeria spp.
Role of finished product testing:
Does not ensure food safety! Focus on preventative controls and employ a pathogen environmental monitoring program to verify the effectiveness of the controls. Act on positive results!
Why is product testing alone not effective?
Contamination after heat processing + during further handling (cutting, slicing). Due to formation of biofilms, which may result in enhanced resistance to sanitisers, disinfectants and antimicrobial agents
A Food Pathogen Control Program can lead to the food processor determining where to focus resources and how to create a plan for remediation.
Figure 1: Transmission routes of Listeria monocytogenes in ready-to-eat (RTE) foods
About the Author
Professor Elna Buys runs the Department of Consumer and Food Science, University of Pretoria
She can be contacted at: elna.buys@up.ac.za
References
EFSA 2017, Listeria monocytogenes contamination of ready-to-eat 1 foods and the risk for human health in the EU (Draft), EFSA Journal
Food Safety Authority Ireland, 2011. Microbial fact sheet: Listeria monocytogenes, issue 1 September 2011
Innovation Center for US Dairy, 2015. Control of Listeria monocytogenes
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