Kyushu University research group has engineered a “smart packaging film” that signals meat spoilage through both visible colour transitions and fluorescence under ultraviolet (UV) light.
The material, evaluated on refrigerated mutton, tracks quality degradation by reacting to ammonia and other volatile compounds emitted as meat decays.
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While natural plant pigments such as anthocyanins are widely studied for tracking acidity changes linked to decomposition, early colour shifts can be difficult to discern under conventional retail illumination.
To overcome this limitation, a research team led by professor Fumihiko Tanaka and associate professor Fumina Tanaka at Kyushu University’s faculty of agriculture partnered with colleagues from Nanjing Agricultural University in China, Ghent University in Belgium, and Nguyen Tat Thanh University in Vietnam.
The substrate uses casein, a milk-derived protein, as its structural base.
Researchers blended this matrix with anthocyanins extracted from black soybean seed coats.
To generate a fluorescent signal alongside the natural colour shifts, the pigments were treated with pyridine.
The resulting compound was merged with zeolitic imidazolate framework-67 (ZIF-67), a porous metal–organic framework material and embedded into the casein structure.
Evaluations compared three formulations containing graduated concentrations of ZIF-67 to gauge freshness detection and meat preservation.
The mid-tier formulation, designated Z2, demonstrated the most effective combination of sensor accuracy, preservation performance, and raw-material consumption.
Compared to pure casein formulations, the Z2 film also exhibited enhanced resistance to moisture, higher antioxidant activity, and stronger antibacterial properties.
During refrigerated storage, mutton degradation generated volatile emissions that activated the indicators.
The Z2 film yielded a distinct fluorescent glow around day six under 365-nanometre UV light, alongside progressive colour transitions visible under standard lighting.
The biopolymer also recorded pronounced degradation and weight loss during soil-burial and seawater trials, showing potential to curb persistent plastic waste.
Subsequent work will focus on testing the film against alternative food matrices and within operational supply chains, alongside evaluations of shelf stability, safety profiles, manufacturing scalability, and cost-effectiveness.
Kyushu University JSPS researcher Xirui Yan said: “We wanted to combine colour changes with fluorescence to make signs of spoilage easier to recognise.
“Colour provides a simple visual indication, while fluorescence under UV light offers a clearer signal when colour differences are difficult to see.”
