New Packaging Solution Reduces Mercury Content in Tuna

Fish is an excellent source of protein, rich in omega-3 fatty acids and essential nutrients. However, consuming certain fish species also exposes people to methylmercury, the most toxic form of mercury. This heavy metal accumulates in fish, particularly predatory species like tuna, as it binds strongly to proteins in their tissues.

The World Health Organization (WHO) ranks mercury among the ten most dangerous chemicals to human health. It can harm the central nervous system, with fetuses and young children being especially vulnerable. As a result, there are specific dietary recommendations for pregnant women regarding tuna consumption.

Mehdi Abdollahi, Associate Professor at the Department of Life Sciences at Chalmers University and coordinator of the DetoxPak project, explains the study’s goal: to improve food safety, enhance human health, and enable better utilization of fish products that currently face consumption restrictions.

A solution containing the amino acid cysteine ​​is poured into a sample of canned tuna. (Source: Chalmers University of Technology/Hanna Magnusson)

The concept of active packaging involves materials—such as a special liquid inside a can—that interact with food during storage. While this technique has been used to extend shelf life, it has never before been applied to improve food safety.

In a previous study, researchers explored coating packaging materials with thiolated silica to capture mercury from canned fish. However, they discovered that the strong binding forces between mercury and the fish proteins prevented effective removal.

Building on this knowledge, they developed a new approach: introducing a water-based solution containing cysteine, a sulfur-rich amino acid naturally found in fish. The idea was that cysteine could attract some of the mercury from the fish tissue, allowing it to bind to the solution instead and be discarded.

The study revealed that the larger the surface area of the fish exposed to the cysteine solution, the greater the mercury absorption. The highest reduction rate—35 percent—was observed when testing ground tuna meat from commercially available canned products. Additionally, researchers found that the absorption limit was reached after approximately two weeks.

A key advantage of this method is that it did not alter the appearance or smell of the fish. Furthermore, cell-based tests confirmed the safety of the developed technology.

“The beauty of this type of packaging is that it remains active while the product is on the shelf. If implemented in industrial production, no additional processing steps would be required. Our findings could significantly increase the safety margin for fish consumption,” says Przemysław Strachowski, first author of the study and former postdoctoral researcher at the Department of Life Sciences at Chalmers University.

This novel packaging technology represents a promising step toward reducing mercury exposure from tuna consumption—without affecting the fish’s taste, smell, or appearance. If adopted on an industrial scale, it could improve global food safety and public health.

Source:  Press release Chalmers University of Technology (6.2.2025) Note: material may have been edited for length and content.