Title: The occurrence of Listeria monocytogenes and microbiological quality of cold smoked and graved fish on the Icelandic retail market

Abstract

Cold smoked and gravad fish products can be naturally contaminated with low numbers of Listeria monocytogenes. This could represent a serious hazard for susceptible people. This studied was conducted to determine and quantify the occurrence of this pathogenic bacteria on the Reykjavik retail market, estimate the remaining shelf life using the Pathogen Modelling Program (PMP) and assess the microbiological quality of cold smoked salmon and trout and gravad salmon products. Evaluation of pH, Aw, aerobic plate count (APC), MPN of total and faecal coliforms, pos/neg and MPN of L. monocytogenes were conducted in 38 samples (14 cold smoked salmon, 10 cold smoked trout and 14 gravad salmon). Aw and pH values were lower for cold smoked trout. APC values were found higher than the ISFT specifications, but in accordance with other works. L. monocytogenes was found more frequently in gravad salmon than any other product. There was found positive, four gravad salmon and one wood cold smoked salmon samples. In most of the samples L. monocytogenes was found at low levels, and high counts were found only in samples stored at high temperatures (retail level). Predictions of the remaining shelf life were higher than the producer specification on the label, except in temperature abused samples. Therefore, the levels of L. monocytogenes found in cold and gravad salmon represent a potential hazard if temperature abuse can occur. The importance of the cold chain at retail and consumer level must be emphasised.