This new sensor can detect the quality of fish in just 2 minutes

The newly developed smart sensor evaluates the quality of fish in a few seconds using enzymes and microneedles. Checking the freshness of fish in conventional methods has always depended on appearance and smell. Clear eyes, shiny gills, and a mild, natural odor usually indicate freshness, while cloudy eyes or an unpleasant odor are considered warnings. But these visual and olfactory signs usually appear in the late stages of corruption.

Chemical changes begin long before fish develop an unpleasant appearance or odor. Now researchers have designed a portable device that can detect the freshness of fish in less than 2 minutes by identifying these initial changes. This sensor can ultimately make the evaluation process of marine products faster, easier and more accurate.

Fish begin to decompose almost immediately after death. One of the first chemical indicators of this process is hypoxanthine (HX). This compound is formed when nucleic acids and other molecules are being broken down. Because HX levels increase rapidly, scientists consider it a reliable indicator of freshness. This method is used for both whole fish and packaged fillets.

However, HX testing currently requires skilled technicians, laboratory equipment, and long analysis time; Factors that make routine testing impractical in markets, cold storage, and even kitchens. The research team consisting of Nikola Folker, Azade Nilghaz and Moamer Dorvisevich tried to design a tool that can be used almost anywhere without the need for complex preparation or large devices.

This device consists of a four by four array of microneedles coated with gold nanoparticles and an HX-reactive enzyme. Microneedles are commonly used in skin care products and medical patches, but here they have a different role. They help the device access the chemical activity beneath the fish’s surface, where the spoilage process begins.

To take the measurement, the sensor is pressed gently on the fish. Very fine needles hold it in place. As the enzyme reacts with hypoxanthine, the electrical signals in the tissue are altered. The sensor reads these changes and determines the freshness based on that.

The researchers tested the new sensor on pieces of fresh salmon that had been left at room temperature for up to 48 hours. This sensor was able to detect hypoxanthine levels up to the level of 500 parts per billion, which according to experts’ classification means very high freshness. The results appeared in about 100 seconds, and the accuracy and sensitivity of the device were consistent with the available laboratory kits.

Although more work is needed for the widespread release of this sensor, the experiment performed shows the high potential of the device. Researchers have announced that this tool can be used for real-time monitoring of food quality. If developed commercially, this tool could benefit seafood distributors, stores, restaurants, and even home cooks.

Consumers often rely on guesswork and trust when purchasing fish. A sensor that can quickly and objectively confirm freshness can reduce food waste, reduce the risk of foodborne illness and increase confidence in seafood. This research suggests that in the future, testing the freshness of fish could be as simple as placing a small device on its surface and waiting a minute. Instead of judging based on smell or appearance, the user can get an accurate and measurable response based on chemical data.

This research was published in ACS Sensors magazine.