How 'smart' hydrogel packaging tells you if your food is still fresh

Researchers at Kyushu University have developed a smart packaging solution that can tell consumers if their food is still fresh without opening the package. The innovative material is a soft, flexible film embedded with a natural plant pigment called anthocyanin, which shifts color as food spoils. Anthocyanins, found in purple sweet potatoes and red cabbage, are sensitive to changes in pH levels, which increase as bacteria multiply and break down proteins in meat. This change in color is visible to the naked eye and provides a reliable indicator of freshness.

To ensure the pigments' reliability, researchers stabilized them using a metal-organic framework (MOF) called UiO66-NH₂. This stabilization protects the anthocyanins from oxygen, light, and heat, which can cause false readings during transport and storage. The team sourced anthocyanins from an affordable and widely available crop, purple sweet potato, and processed them into a powder.

In their study, published in Chemical Engineering Journal, the researchers tested the material using pork. They found that as the meat spoiled, the anthocyanin-loaded MOF changed color from purple-red to yellow-green, providing a clear and reliable freshness signal at every stage. The self-healing properties of the material were also demonstrated, with cuts quickly healing and the packaging regaining 99% of its tensile strength within two hours.

The potential applications of this smart packaging technology extend beyond food preservation. The team is exploring the possibility of developing a companion smartphone app that would allow manufacturers, logistics companies, and consumers to monitor food quality in real time using the smart packaging. This innovation could lead to more reliable food safety and extend the shelf life of perishable goods.