Purpose: To evaluate the prevalence of Listeria spp. in selected 3 categories of Not-Ready-To-Eat finished frozen products from four different regions of United States.
Methods: At least three (3) different brands of frozen potato products (hash browns, French fries and tater tots) and frozen vegetables (frozen peas, corns, carrots and mixed vegetables), as well as 10 different frozen entrees were purchased from grocers across 4 different regions of the US (Northeast, Midwest, South and West). Products were coded to ensure blind testing. Products were then sampled (25 g), enriched and analyzed for Listeria spp. using BioMerieux’s VIDAS Listeria (LIS) assay. Enrichments providing suspect assay results were confirmed by streaking to MOX media and evaluating for typical colonies. Typical colonies were considered confirmatory for Listeria spp.
Results: A total of 144 analyses (36 frozen potato, 48 frozen vegetable, 60 frozen meals or their individual components) were performed and 13 samples (6 frozen potato products, 6 frozen vegetable products, 1 component of 1 frozen meal) were positive (9%) for Listeria spp. Positive samples were found from all four regions.
Significance: Because 9% of products tested were found positive for Listeria spp., this could indicate the need for the Not-Ready-To-Eat frozen food industry to further evaluate their production environments, with emphasis on the importance of cleaning and sanitizing. Additional intervention measures, along with proper cooking instructions for consumers, can also play a part to minimize potential risk in these types of products.