Fish is often considered a source of nutrition. However, the presence of mercury, particularly methylmercury, in fish poses significant health risks, especially for vulnerable populations such as pregnant women, fetuses, and young children. Chronic exposure to methylmercury can lead to serious neurological and developmental problems, making it a global public health concern. Despite efforts to reduce mercury emissions, effective methods to mitigate mercury absorption through fish consumption have not been found until now.
A groundbreaking study published by scientists from Chalmers University of Technology and the Swedish University of Agricultural Sciences has introduced a new approach to reducing mercury levels in fish during post-packaging storage, offering a promising solution to expand the safe consumption of seafood products.
The innovative method, published in the journal Global Challenges, utilizes a simple, food-safe aqueous solution containing cysteine, an amino acid known for its mercury-binding properties, to extract mercury from fish proteins. The extracted mercury is stabilized in the solution without the need for pH adjustments, making the process efficient and practical for industrial applications.
The science behind the method
Mercury, particularly in its methylmercury form, binds strongly to sulfur-containing amino acids in fish proteins. This strong affinity makes it difficult to remove mercury from fish tissues. The new method addresses this challenge by using cysteine, which contains thiol groups that compete with fish proteins for mercury binding. When fish is treated with a cysteine solution, the mercury is displaced from the proteins and stabilized in the solution.
The study demonstrated that using a 1.2% cysteine solution could reduce mercury levels in canned albacore tuna by 25% to 35%, depending on the type of fish product and the exposure time, which can extend up to two weeks. This reduction is significant, as it directly lowers the risk of mercury exposure for consumers.
“Our study shows that there are alternative approaches to addressing mercury contamination in tuna, rather than limiting consumption. Our goal is to improve food safety and contribute to better human health, as well as to make better use of foods that are currently subject to certain restrictions,” says Mehdi Abdollahi, Associate Professor at Chalmers’ Department of Life Sciences and coordinator of a project called DetoxPak.
Active packaging used to reduce mercury levels
The concept of so-called active packaging involves developing materials, such as a liquid inside a can, that interact with food during storage, for example, to extend shelf life. However, this concept had never been used before to improve food safety.
In a previous study, the researchers investigated the possibility of coating packaging with thiolated silica to capture mercury from canned fish. What they observed was that the forces binding mercury within tuna tissue prevent its release.
Proteins in tuna tissues, particularly sulfur-containing amino acids, bind strongly to mercury and accumulate it due to the strong interactions involving the thiol groups of these amino acids.
“Considering this, we decided to add one of them, cysteine, to an aqueous solution in which fish meat could be soaked. We believed that this could extract some of the mercury, which would then bind to the solution and be discarded. Further research is needed to address the removed mercury,” says Przemysław Strachowski, first author and, at the time of the study, a postdoctoral researcher at Chalmers’ Department of Life Sciences.
A Two-step process to enhance safety
The proposed method involves a two-step process:
- Mercury Extraction: The fish is treated with an aqueous solution containing cysteine, which extracts mercury from the fish proteins. This step is particularly effective during the shelf-storage period, as it does not require additional processing steps during production.
- Mercury Adsorption: The extracted mercury is then adsorbed onto thiolated silica, a material known for its strong affinity for mercury. The thiolated silica can be incorporated into the packaging as sachets filled with adsorbent, providing a convenient and effective way to capture and remove mercury from the solution.
While the study found that the presence of cysteine can hinder mercury adsorption onto thiolated silica, the overall process still offers a significant reduction in mercury levels. This makes it a viable option for active food packaging solutions, where the goal is to enhance the safety of seafood products without compromising their quality or nutritional value.
Practical implications for the food industry
One of the most appealing aspects of this method is its simplicity and potential for industrial application. The use of a single-component aqueous solution without the need for pH adjustments makes it easy to integrate into existing packaging processes. Additionally, the method can be applied to various seafood products, including canned or jarred fish with water-based sauces.
For consumers, this innovation offers a straightforward way to reduce mercury exposure. After opening the package, the water solution containing the extracted mercury can be discarded, ensuring that the fish is safer to consume. This approach not only improves food safety but also aligns with consumer preferences for minimally processed, nutrient-rich foods.
Addressing a global health issue
Mercury pollution is a persistent environmental and public health issue, with the World Health Organization (WHO) listing it among the top chemicals of major public health concern. The bioaccumulative nature of mercury means that even small amounts can have long-term consequences, particularly for populations that rely heavily on fish as a staple food.
By developing a method to reduce mercury levels in fish during post-packaging storage, this study offers a practical and innovative solution to a pressing global problem. It represents a significant step forward in ensuring the safety of seafood products, protecting vulnerable populations, and promoting sustainable seafood consumption.
Conclusion
The new approach of using cysteine-based solutions to reduce mercury content in fish is a game-changer for the food industry and public health. By leveraging cysteine’s natural affinity for mercury, this method provides an effective, simple, and scalable solution to mitigate mercury exposure from fish.
The study was funded by Formas.
Contact
Przemysław Strachowski
Department of Life Sciences – Food and Nutrition Science, Chalmers University of Technology
Gothenburg, SE 412 96 Sweden
Email: pawelpr@chalmers.se
Reference (open access)
Strachowski, P., Mandava, G., Lundqvist, J., Bordes, R., & Abdollahi, M. (2024). New Insight into Mercury Removal from Fish Meat Using a Single-Component Solution Containing cysteine. Global Challenges, 8(11), 2400161. https://doi.org/10.1002/gch2.202400161
Strachowski, P., Mandava, G., Lundqvist, J., Bordes, R., & Abdollahi, M. (2025). Development of mesoporous silica-based active coatings for methylmercury removal: Towards enhanced active packaging. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 704, 135562. https://doi.org/10.1016/j.colsurfa.2024.135562
