NIFES has analysed samples of various sushi products. The content of undesirable substances was generally low, but the products showed varying microbiological quality. In no case did the level of undesirable substances exceed the EU’s upper limit, where such limits have been set.
In the project ”Undesirable substances in processed seafood products 2008”, under an assignment for the Norwegian Food Safety Authority , NIFES analysed the content of undesirable substances and the microbiological quality of various sushi products from retailers and restaurants in Bergen and Trondheim. Each sushi sample consisted of a mixture of different seafood products, rice, vegetables, condiments and, in some cases, sauces.
Low levels of undesirable substances
A total of 25 samples were examined for the presence of several undesirables, including heavy metals, PCB, DDT, dioxins, dioxin-like PCBs and bromated flame retardants. The content of undesirables was low in all of the samples analysed, and the level of heavy metals, the PAH compound benzo(a)pyrene, dioxins and dioxin-like PCBs was below the EU’s upper limits for these substances. The level of the undesirables which were the subject of the analysis (arsenic, inorganic arsenic, tributyl tin, several PAH compounds, PCB, DDT and other chlorated pesticides as well as bromated flame retardants) was very low, and in many cases below the quantification limit. Here, no upper limit values have been established by the EU. Residues of pharmaceuticals (seven different compounds) were not found in any of the 13 samples analysed.
A total of 50 samples were analysed for L. monocytogenes, and the bacterium was found in 20% of the samples. In all of the positive samples, the number of L. monocytogenes was less than 10 bacteria per gram, and thus well below the EU’s upper limit of 100 bacteria per gram of fresh food. This upper limit applies at the end of the shelf life and assumes that the product is intended for consumption by healthy adults.
Given the short shelf life that applies sushi, t L. monocytogenes has limited possibility to multiply.
E. coli, enterococci, Salmonella and parasites
E. coli and enterococci are used as indicator organisms for faecal contamination, and thus a possible health risk. This finding indicates a potential for improved hygienic standards/routines in production of sushi. E. coli was found in a total of 18 of the 50 samples analysed. In an international context, bacteria related to Salmonella are among the main causes of infections from food products. However, only very rarely do seafood products produced in Norway contain Salmonella, and none of the 50 sushi samples analysed contained this bacterium. Some parasites, such as nematodes can represent a threat to human health, but no parasites were found in any of the samples examined.
Each year, the National Institute of Nutrition and Seafood Research (NIFES) analyses a variety of processed seafood products from the Norwegian market for the Norwegian Food Safety Authority. Herring and mackerel products were analysed in 2005 and 2006, respectively, and in 2007 trout and salmon products were analysed for both chemical and microbiological parameters.
Bjørn Tore Lunestad, Surveillance Research Programme