Kyushu University develops dual-mode fluorescent packaging film for mutton freshness
A casein-based smart film indicates meat spoilage via ambient color shifts and 365 nm UV fluorescence activation in laboratory trials.
Researchers at Kyushu University, in collaboration with institutions from China, Belgium, and Vietnam, have developed a biodegradable dual-mode smart packaging film for monitoring chilled mutton freshness, according to a study published in Chemical Engineering Journal sciencedirect.com
Chemical Engineering Journalsciencedirect.comOpen source ↗. The composite material integrates natural pigments and porous frameworks into a milk protein matrix to provide visual color changes alongside ultraviolet fluorescence detection.
Sensor design and barrier properties
The formulation relies on a casein (CAS) base incorporating pyridine-modified black soybean seed coat anthocyanins (mBSSC) and the zeolitic imidazolate framework ZIF-67. The mBSSC/ZIF-67 hybrid disperses uniformly within the protein network, yielding a compact structure with stable mechanical characteristics. Compared with pure casein films, the hybrid additive cut water vapor permeability by half, from 12.4 × 10⁻¹¹ to 6.2 × 10⁻¹¹ g·m⁻¹·s⁻¹·m²·Pa⁻¹, while boosting water resistance, antioxidant capacity, and antibacterial properties.
Among the tested variants, the team identified the CAS/mBSSC/Z2 formulation as optimal for performance and material efficiency. The film tracks spoilage by detecting volatile basic nitrogen compounds, including ammonia, released by meat during storage.
Spoilage detection and shelf-life extension
During refrigerated mutton storage tests, the film demonstrated two complementary indicator modes sciencedirect.com
Chemical Engineering Journalsciencedirect.comOpen source ↗. Under ambient lighting, the indicator undergoes gradual visible color changes, while illumination with 365 nm ultraviolet light activates bright fluorescence at approximately Day 6. This allows routine visual inspection by consumers as well as high-contrast verification under low-light conditions with portable UV emitters.
Beyond passive sensing, the CAS/mBSSC/Z2 film actively delayed mutton deterioration. The material postponed the time required for total volatile basic nitrogen (TVB-N) to hit the 15 mg/100 g threshold until Day 10. Furthermore, it restricted the final microbial load to 8.8 log CFU/g, compared with 12.6 log CFU/g observed in the Z1 formulation group. Soil-burial and seawater tests also confirmed substantial mass loss and physical disintegration of the tested films.
