Canned tuna is the ally of many meals, a fish rich in proteins and omega‑3, at the heart of the Mediterranean diet. But behind this healthy image there is a persistent concern: its mercury content, a heavy metal whose effects on the nervous system make many consumers hesitant. A Swedish team, however, claims to have found a natural solution capable of reducing this contaminant by up to 35% in canned tuna, without changing either the taste or appearance. A breakthrough that could transform our cans tuna.
A natural solution in sight
Large predatory fish like tuna accumulate mercury throughout the food chain. In France, health authorities regularly remind people to limit fish to around two servings per week, because some fillets can contain heavy metals, especially for pregnant women, breastfeeding women and young children.
The paradox is clear: tuna remains an excellent source of omega-3 beneficial for the heart and brain, but these vulnerable populations must reduce their consumption. Enough to encourage researchers to explore something other than the simple “eat less”: the trail of a well-known amino acid, cysteine.
Cysteine and canned tuna
Scientists from the Swedish University of Agricultural Sciences and Chalmers University of Technology tested adding cysteine to the water surrounding canned tuna. The chemist Przemysław Strachowski sums up their choice: “We chose cysteine for its ability to bind strongly to mercury. This mechanism allows some of the mercury to be extracted from the fish so that it attaches to the solution and is eliminated.“, he explains.
Concretely, the tuna samples were immersed in an aqueous solution containing this natural amino acid. Laboratory analyzes show a 25 to 35% reduction in mercury concentration, with no change in the smell or appearance of the fish. The longer the flesh remains in contact with the solution, the more mercury is extracted, a process that continues for up to two weeks after treatment.
Towards safer cans of tuna
This simplicity paves the way for cans of tuna with active packaging, where the cysteine would be integrated directly into the covering liquid. “The advantage of this type of packaging is that it remains active for the entire shelf life of the product“, specifies Przemysław Strachowski.
Researchers remain cautious: we still need to manage the mercury captured and show that the process works on a large scale. “Our goal is to improve food security and contribute to better human health“, underlines Mehdi Abdollahi, food scientist at Chalmers University of Technology and researcher of the study. While waiting for possible cans of tuna enriched with cysteine, the advice for moderate consumption, especially for pregnant women and children, therefore remains relevant.