Aquaculture for all

Microbiological Quality of Shellfish Good, Says NIFES

Food safety & handling +1 more

NORWAY - National Institute of Nutrition and Seafood Research (NIFES) has determined the content of undesirable substances and microorganisms in samples of shellfish collected in 2008, and found that the quality of the shellfish was generally good.

Through its Shellfish Surveillance Project, on behalf of the Norwegian Food Safety Authority, NIFES has carried out microbiological examinations of the presence of E. coli, enterococci and Salmonella, as well as chemical determination of undesirable substances (metals, DDT, PCB, dioxins, brominated flame retardants and PAH) in samples of shellfish collected in 2008.

Generally good microbiological quality

Shellfish can take up intestinal bacteria such as E. coli, enterococci and Salmonella if they are present in the surrounding water. Determination of the amount of E.coli and enterococci is used as an indication of faecal pollution, and thus of possible health risk.

No Salmonella was detected in any of the 61 samples examined, but enterococci were found in 8 of the 388 samples examined.

Of a total of 388 samples examined for E. coli, 337 (87 per cent) had concentrations that were within the limit set for classification of the area as an A zone, which means that the shellfish can be sent directly for consumption. A total of 46 samples had concentrations of E. coli corresponding to the B zone, while the level found in five samples corresponded to the C zone. Shellfish from B and C zones require relaying or heat treatment before they can be sold.

Generally low level of undesirable substances in shellfish

The concentrations of metals in blue mussels were at the same level as in previous years, and none of the heavy metals cadmium, mercury or lead were present in concentrations above the EU’s upper limits. The concentrations of dioxins and dioxin-like PCBs, PCB7 and brominated flame retardants were low in the nine blue mussel samples examined for these substances.

Previously, high levels of cadmium and lead have been found in the kidney of horse mussels, and high levels of cadmium have been found in the digestive gland of scallops. The Norwegian Food Safety Authority therefore provides dietary advice on the consumption of horse mussels and scallops, recommending to remove the kidney from horse mussels before they are prepared for consumption, and to eat only the muscle and roe of scallops.

For the surveillance programme, the entire contents of the horse mussels are analysed, while for scallops it is only the muscle and roe that are analysed. The two samples of horse mussels that were analysed showed that the concentrations of cadmium were above the EU's upper limit of 1.0 mg/kg wet weight, while the lead concentrations were below the upper limit of 1.5 mg/kg wet weight. This emphasises the importance of the dietary advice. The concentrations of polyaromatic hydrocarbons (PAH) in horse mussels were below the quantification limit. The muscle and roe of the scallop samples had generally low concentrations of both heavy metals and PAH.

Further Reading

- You can view the full report (in Norwegian with English summary) by clicking here.