Self-Repairing Freshness Films

Kyushu University Unveiled Its Plant-Pigment Indicator Film

Researchers at Kyushu University developed a plant-pigment indicator film that combines a natural freshness indicator with self-healing properties. The material uses anthocyanins, plant-derived pigments that change from purple-red to yellow-green as food spoilage raises pH levels, providing a visible freshness signal without opening the package.

To improve stability, the team anchored the pigments to a UiO66-NH₂ metal-organic framework before incorporating them into a biodegradable hydrogel film. In pork tests, the material responded continuously as spoilage progressed and extended shelf life by about 12 hours compared with untreated samples. When cut and pressed back together, the film became nearly invisible within minutes and recovered 99% of its tensile strength within two hours.

For consumers and brands, the material could improve freshness visibility, reduce food waste and help maintain package integrity after minor damage.

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