A european food fraud investigation has uncovered tainted tuna. Tuna destined for canning was illegally treated with chemicals to transform it from brown to red, fooling customers into thinking it was fresh. Fresh tuna sells for twice the price of canned tuna.
The chemicals used are carbon monoxide and nitrites, the same substances often used in processed meats. Illegally treated tuna may contain high amounts of histamine which can cause serious allergic reactions – histamines result from spoiling, something masked by faked reddening. Nitrites may also result in the formation of carcinogenic substances known as nitrosamines.
More than 51 tonnes of the fish were seised and more than 380 samples taken. In some countries investigations took place on fishing vessels and in processing plants. In others sampling took place at distribution and retail levels.
In 2016, whistle blowers raised the alarm. Tuna destined for canning (frozen in brine after capture at temperatures of -9°C instead of – 18°C) was being illegally treated to alter the colour of it. 5 million tuna portions are treated this way per week, or 25 000 tons per year, estimates the report.
The report reveals an interesting fallacy: fish frozen at -18°C is no longer fresh, making most of what is sold as “fresh” actually thawed frozen fish.
There are methods to detect the use of carbon monoxide, but there are currently no harmonised methods which can prove that tuna has been treated with nitrites, said the European Commission report.
What should consumers do?
Be aware that red tuna is not always fresh. If the fish is a bright, unnatural-looking shade of red, it may have been illegally treated.
The challenge with “fresh” food is that it isn’t clear what is in it. Labels make no mention of additives or what the animal was fed. Fish feed is a global industry. Fish from the Baltic sea could end up in fish feed that is fed to a fish in Australia. In addition, animal feed is often treated with chemical preservatives. Until labels show what has been added and what the animal has been fed, and the label can be trusted, selecting uncontaminated products will remain a game of chance.
European Commission report (in English)