Minimising risks of dairy product contamination

Recent outbreaks of Listeria monocytogenes in ice-cream in the US have been linked to contamination of the final product in the food-processing environment. Historical control measures through heat (pasteurisation) have had a major impact on reducing the occurrence of listeriosis, but contamination of processed dairy products still occurs. More understanding of ecological niches within dairy manufacturing plants is needed.

The International Dairy Federation has now published guidance outlining additional actions that can be taken in the production process to minimise the risk of Listeria contamination in dairy products.

Between 1985 and 2019, there have been 40 confirmed major recorded outbreaks of listeriosis associated with commercially pasteurised dairy products. In most cases where a source was identified, L. monocytogenes was found in niches in the dairy processing environment and contamination of final product occurred due to cross-contamination post pasteurisation.

In order to further minimise risk of Listeria contamination in the dairy production process, IDF has developed its new Bulletin ‘Ecology of Listeria spp. and Listeria monocytogenes - Significance in Dairy Production’. The Bulletin summarises risk areas and measures that should be taken in the food production process to minimise the risk of L. monocytogenes contamination in dairy products.

François Bourdichon, main author of the publication and present Chair of the IDF Standing Committee on Microbiological Hygiene, said: “Effective management and hazard analysis within the dairy processing environment can minimise the likelihood of contamination with L. monocytogenes, therefore giving better food safety assurance.”

Recent advances in source tracking can help characterise resident strains, their resistance to cleaning agents and adherence to dairy product contact surfaces. Control measures can be customised for a better fit for purpose, with better hygienic design and a good rationale for the use of chemical cleaning agents.

Good milking practices reduce the prevalence of L. monocytogenes in processed dairy, while pasteurisation reduces the contamination (if any) of processed milk with L. monocytogenes. Process environment monitoring guards against re-contamination.

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