Reducing mercury content in packaged tuna via an ‘active’ solution in the can | 06-03-2025 |

Researchers from Chalmers University of Technology have come up with a novel approach to packaging canned tuna infused in the water-based solution of amino acid cysteine. It was shown to remove up to 35%  of the accumulated mercury in canned tuna, significantly reducing human exposure to mercury via food, the report claims. 

Fish and other seafood, provide people with a broad variety of essential nutrients in their diet However, the consumption of some fish also exposes people to the most hazardous form of mercury, methylmercury. This accumulates in fish (especially those species higher up the food chain, such as tuna) as it binds to proteins in the tissues. 

According to the World Health Organisation (WHO), mercury is one of the ten most harmful chemicals for humans. Exposure can damage the central nervous system, with foetuses and young children being particularly sensitive to the effects. That is why dietary recommendations for pregnant women advise caution with tuna consumption

“Our study shows that there are alternative approaches to addressing mercury contamination in tuna, rather than just limiting consumption. Our goal is to improve food safety and contribute to enhanced human health, as well as to better utilise food that is currently under certain restrictions,” says Mehdi Abdollahi, associate professor at the Department of Life Sciences at Chalmers and coordinator of a project called DetoxPak.

In a previous study, the researchers investigated the possibility of coating packages with thiolated silica to capture mercury from canned fish. What they observed, was that the forces binding the mercury within the tuna tissue prevented it from being released. Proteins in tuna tissues, particularly sulphur-containing amino acids, strongly bind and accumulate mercury due to the strong interactions involving thiol groups from these amino acids.

"By knowing that, we decided to add one of them, cysteine, to a water solution in which fish meat can be immersed. We believed this would allow some of the mercury to be drawn out and instead bind to the solution and be discarded. Further research is needed to take care of the removed mercury,” says Przemys?aw Strachowski, first author and, then, a postdoc at the Department of Life Sciences at Chalmers. 

In the study, the researchers discovered that the greater the surface area of fish flesh in contact with the cysteine solution, the higher the mercury uptake. The highest value of mercury reduction, 35%, was reached when testing canned minced tuna, from regular grocery stores. They also discovered a maximum threshold of two weeks, after which no further changes occurred..

“The beauty of this type of packaging is that it is active while the product is on the shelf. No additional production steps would be needed if a method like this were used industrially. The application of our results could increase the safety margin for fish consumption,” says Strachowski.

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