A pH-responsive and antibacterial double-layer smart nanofiber film (PCL/AlPc-PCL/PVA/CS/ACN) for pork preservation monitoring

Current smart cling films for pork preservation often face two key challenges: either they lack real-time freshness monitoring capabilities, or their antibacterial components rely on visible light—limiting penetration depth and easily inducing lipid oxidation in pork. To address these gaps, this work fabricated an electrospun bilayer smart cling film with integrated preservation and monitoring functions. The film comprises a hydrophilic outer layer (polycaprolactone [PCL]/polyvinyl alcohol [PVA]/chitosan [CS]/anthocyanin [ACN], for pH-responsive color indication) and a hydrophobic inner layer (PCL as the matrix, loaded with aluminum phthalocyanine [AlPc], for near-infrared-driven antibacterial activity). We systematically investigated the effect of AlPc loading (5 %–15 %) on film performance. Results showed that the film with 15 % AlPc exhibited the highest level of comprehensive properties among the tested groups: its antibacterial and antioxidant capacities were significantly enhanced, alongside improved physical characteristics—hydrophobicity of the inner antibacterial layer increased by 17 % (in terms of water contact angle), and water vapor transmission (WVT) was reduced by 19 %. Importantly, the film displayed distinct color changes (light red to dark red) in pH 3–11 buffer solutions and during pork storage, enabling real-time freshness monitoring. Moreover, it extended the freshness period of pork to 5 days. These findings demonstrate that the prepared bilayer film effectively addresses the limitations of existing cling films, offering significant potential for simultaneous pork shelf-life extension and freshness monitoring.