For generations, the freshness of fish has been judged by sight, smell, and touch, methods that are often subjective and unreliable.
But these traditional methods, while familiar, are often subjective and unreliable. Now, scientists have developed a portable device capable of determining fish freshness in under two minutes by detecting early chemical changes that signal spoilage.
The new technology works by identifying rising levels of hypoxanthine (HX), a compound that forms as nucleic acids and other molecules in fish begin to break down.
Because HX increases rapidly as fish deteriorates, researchers describe it as one of the most reliable scientific indicators of freshness. The device is suitable for both whole fish and packaged fillets, making it ideal for markets, processing plants, and retail outlets.
The international research team led by Nicolas Voelcker, Azadeh Nilghaz, and Muamer Dervisevic set out to design a simple tool that could be used almost anywhere without the need for complex machinery or laboratory preparation.
Their goal was to create a practical solution for real-life environments where electricity, refrigeration, and advanced testing facilities are limited, conditions that reflect the reality in many parts of Tanzania.
At the heart of the innovation is a small four-by-four microneedle array coated with gold nanoparticles and a specialized enzyme that reacts specifically with hypoxanthine.
While microneedles are commonly used in skincare and medical patches, in this case they serve a different function: penetrating just beneath the surface of the fish where spoilage begins.
To use the device, the sensor is gently pressed against the fish. The tiny needles anchor it in place as the enzyme reacts with the hypoxanthine present. This reaction causes subtle electrical changes within the flesh, which are then translated into a measurable freshness reading.
If developed for commercial use, the invention could significantly benefit seafood distributors, supermarkets, restaurants, and even ordinary households.
Currently, consumers often rely on trust, experience, and guesswork when purchasing fish. A tool that provides quick, objective confirmation of freshness could greatly reduce food waste, lower the risk of foodborne illness, and increase public confidence in seafood products.
The study suggests that in the near future, testing fish for freshness could become as simple as pressing a small device onto its surface and waiting less than a minute for results.
The invention has already drawn praise from experts, who say it addresses a long-standing challenge that has often been overlooked.
“Many people may think this is not a serious problem, but globally, we still depend on smell, color, texture, and firmness to judge fish quality. These methods do not always give accurate results,” said a local food safety expert, who requested anonymity.
For ordinary consumers, the innovation speaks directly to everyday struggles.
“I am a housewife, and I care a lot about what my family eats. But when I go to the market to buy fish, I have no reliable way to measure quality apart from how it looks,” said Ms Rehema, a Dar es Salaam resident. “Sometimes you trust your eyes and still end up disappointed.”
Businesspeople in the fisheries sector have also welcomed the development, describing it as a potential driver of higher standards and stronger consumer trust.
Stakeholders are now urging the government and local research institutions to seize the opportunity and invest in adapting the technology for domestic use.
“I see this as a real opportunity for our country,” said Juma Bakari, a resident of Kigamboni in Dar es Salaam. “With the expertise we have, we can be among the first to develop and improve this technology locally so that it meets our own market needs. The research already shows it is possible; what remains is for us to act.”
As Tanzania continues to prioritise food safety, industrialisation, and value addition in the fisheries sector, such innovations could play a key role in protecting consumers, supporting traders, and strengthening the credibility of fish products both locally and for export.