Detection and Enumeration of Listeria monocytogenes in Refrigerated and Frozen Seafood Products

摘要

The traditional frozen, battered and breaded seafood portion is a low-risk food safety concern, since this product is usually fully cooked prior to consumption. In addition, growth of bacterial pathogens, such as Listeria monocytogenes, is unlikely tooccur during frozen storage unless there is significant temperature abuse. However, an increasing number of supermarkets and convenience stores are interested in selling unfrozen, raw, partially cooked or fully-cooked, battered and breaded seafood. Manytypes of refrigerated foods, such as ready-to-eat sandwiches, meat salads.frankfurters, and cold smoked fish products, have been recalled from the marketplace because of contamination with L monocytogenes. This survey examined frozen and refrigerated, raw, partially cooked and fully cooked seafood products (n = 112) for the presence of this bacterial pathogen. Qualitative test results revealed that 16 of the 112 (14.3%) samples were positive for Listeria species. Among the raw and partially cooked battered and breaded fish portion samples, primarily pollock, cod, or whiting, L. monocytogenes was identified in 9 of 79 (11.4%) products. None of the 12 fully-cooked products were positive for Listeria spp. Separate 50 g portions of all L. monocytogenes-positive samples were analyzed quantitatively by dilution in buffered peptone water and direct plating onto PALCAM, OXA and ALOA agar media. The concentration of L monocytogenes was less than 50 CFU/g for all positive samples. Since L monocytogenes survived in these products, antimicrobial interventions should be considered and manufacturers should provide consumers with a recommended internal cooked product temperature along with easily understood cooking instructions.