Norwegian officials have uncovered a case of fish fraud during a national control operation.

The Norwegian Food Safety Authority (Mattilsynet) took 15 samples of fresh and frozen tuna from importers and wholesalers and found an illegally high level of carbon monoxide in one sample.

Low values of carbon monoxide were discovered in other samples but these may come from natural sources. Treatment of unprocessed fish with carbon monoxide as an additive is not permitted in Europe because it can give tuna a red color, making it look fresher, hiding poor quality and potential high levels of histamine.

“There is no suspicion that carbon monoxide has been added to the tuna in Norway, but this has happened in the exporting country. Most of the tuna imported into Norway comes from Asia. The importers are responsible for ensuring that the goods they bring into the country are legal to sell. It is important that importers are aware of the risk of fraud and take samples of the tuna they import,” said Marit Forbord, from Mattilsynet.

The Norwegian Food Safety Authority informed the importer about the result and that the fraud is being followed up. The business has been in contact with its supplier.

Findings were made in the annual action against food fraud and crime called Operation Opson XII, which was coordinated by Europol.

A similar control undertaken in 2018 found the illegal use of additives in six out of 31 samples. As in 2018, the use of additives such as carbon monoxide, nitrite, nitrate and ascorbic acid, and histamine levels were included in the analysis.

“Those who buy illegally processed tuna are tricked into thinking that they are buying a high-quality food product. This is food fraud and in the worst case it can pose a health risk,” said Forbord.

Shellfish controls
Norway has also released findings from another control of 187 shellfish samples collected by the Norwegian Food Safety Authority throughout 2022.

Of these, 128 were blue mussels, 20 were scallops, 18 were flat oysters, six were pacific oyster, four were banded carpet shells, one was common whelk, four were northern horse mussel, three were razor clams, and two were green sea urchin. Overall, 186 samples were analyzed for E. coli and 42 were tested for Salmonella.

Results found 88.7 percent had a content of E. coli below 230/100-gram. This is the limit for classifying a locality to a so-called A-area, which allows harvest for direct consumption. In 21 samples, E. coli was above this level. Of these, 19 were blue mussels, one was Pacific oyster, and another was European flat oyster. The highest value of E. coli measured was 5,400/100g. All samples analyzed for Salmonella were negative.

Another 279 samples were sent to the Institute of Marine Research directly by farmers including 271 blue mussels, six flat oysters, and two green sea urchin. Of these, the E. coli content was under 230/100g in 241 samples. The remaining 38 samples with E. coli above 230/100g were all blue mussels. The highest observed concentration of E. coli in blue mussels was 160,000/100g.

Samples of bivalves and other mollusks taken during 2022 by Mattilsynet district offices for analysis of undesirable substances included 30 mussels, 11 great scallops, four European flat oysters, and one each of banded carpet shell, common whelk, green sea urchin, and horse mussel.

They were tested for copper, zinc, arsenic, selenium, silver, cadmium, lead, mercury, and inorganic arsenic. Samples taken during fall were analyzed for TBT and the persistent organic pollutants (POPs) polychlorinated biphenyls (PCB6), dioxins and dioxin-like PCBs, polybrominated flame retardants (polybrominated diphenyl ethers (PBDE) and polyaromatic hydrocarbons (PAH).

Results from the metal analyses were generally low and findings on dioxins and dioxin-like PCBs, PCB6 and PBDEs were very low.

Two samples of European flat oyster had cadmium concentrations above the upper limit of 1 mg/kg wet weight with 1.1 and 1.4 mg/kg wet weight. No samples submitted by industry exceeded any maximum levels for metals.