Kyushu University smart film changes colour as meat spoils

The Story in Brief

Researchers at Kyushu University in Japan have developed a smart packaging film that changes colour from purple-red to yellow-green as meat spoils. The film uses anthocyanin pigment extracted from purple sweet potatoes, anchored to a metal-organic framework to prevent fading. It also heals small cuts, recovering 99% of its tensile strength within two hours. The work, published in Chemical Engineering Journal, is part of a growing field called intelligent packaging that monitors food condition without opening the package. The film responded clearly in tests with pork, offering a gradual colour change rather than a simple fresh-or-rotten signal.

The material is a plant-based, biodegradable hydrogel, making it potentially more environmentally friendly than conventional plastic. The researchers attached the pigment to a protective scaffold called UiO-66-NH₂ to keep it stable under heat, light and oxygen. The film's self-healing property could prevent bacteria from entering through tears caused during transport. The technology is still at an early stage, and commercial availability is not yet announced.