Pasteurised milk is sold with a use-by-date which means it should not be consumed after that date for food safety reasons. From time to time it has been suggested that the use-by-date should be replaced with a best-before-date partly to reduce food wastage.

Nathan Devlin, a final year honours degree student at CAFRE’s Loughry Campus has investigated the microbiological quality of commercial HTST milk produced by two commercial plants in Northern Ireland at the use-by-date. All samples were stored at 3°C.

Several jurisdictions have regulations for microbial limits in pasteurised milk with the Grade “A” Pasteurized Milk Ordinance (PMO) in the US well known. This sets a total count limit of 20,000 cfu/ml and a maximum of 10 coliform/ml in pasteurised milk. Other jurisdictions tend to use higher total counts and replace coliforms by typically <10 cfu/ml of Enterobacteriaceae. Limits for Bacillus cereus are also included in some jurisdictions.

Nathan found that > 85% of the samples analysed failed the PMO standard for the total count and >27% of samples failed the EU limit of <10 cfu/ml of Enterobacteriaceae at the use-by-date. No issues were found with the counts of B. cereus.

Based on the results, Nathan recommends that a use-by-date for pasteurised milk is maintained and that further work is undertaken to identify and control the post-process contamination that is responsible for the results found.

Nathan Devlin can be contacted at nathan.d123@hotmail.co.uk .