Listeria monocytogenes has been detected in a number of frozen vegetables tested in Ireland. The Food Safety Authority of Ireland (FSAI) said findings show a potential risk of illness for consumers who have non-ready-to-eat (RTE) frozen vegetables, fruits or herbs without cooking.
After a 2015 to 2018 listeriosis outbreak in Europe traced to uncooked non-RTE frozen sweetcorn and other vegetables, a national microbiological survey on frozen vegetables, fruits and herbs sold in Ireland was done between August and November 2019 by the FSAI. More than 50 people were sick from five countries and 10 died in the outbreak linked to vegetables made by Greenyard in Hungary.
Of 906 samples tested for Listeria monocytogenes in Ireland, 27 were positive, and 21 were non-RTE frozen vegetables. It was detected in four samples of RTE frozen fruits and two RTE frozen vegetables.
Low levels but a risk with frequent consumption
Listeria monocytogenes was below the limit of detection at under 10 colony forming units per gram (cfu/g) for most samples, apart from three which were non-RTE frozen petit pois, non-RTE frozen diced onion, and frozen chopped basil.
The work found such low levels posed a minimal risk to people who are in good health.
“However, the risk could be higher for consumers who are immunocompromised, or if consumer preparation and handling practices allow any of the Listeria monocytogenes contamination present in the non-RTE frozen vegetables to increase at the point of consumption to levels high enough to potentially cause listeriosis,” said the study.
Of 828 samples tested for Listeria spp., 37 were positive. No samples were contaminated with Salmonella.
Presence of E. coli as a hygiene indicator was assessed in 887 frozen vegetable, fruit and herb samples. Ten were contaminated with E. coli at levels of between 20 and 100 cfu/g and two were RTE frozen vegetables. There were two non-RTE samples of frozen spinach with E. coli levels of 1,100 cfu/g and 570 cfu/g.
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