Intelligent double-layer fiber mats with high colorimetric response sensitivity for food freshness monitoring and preservation

Recently, colorimetric films with antibacterial or antioxidant activity have received growing attentions. In this work, novel intelligent double-layer fiber mats were developed via electrospinning technique for pork freshness monitoring and preservation. The mats are composed of a layer of pullulan-purple sweet potato extract (PL-PSPE) and a layer of zein-glycerol-carvacrol (ZN-GL-CA). The colorimetric response and antibacterial activity were respectively dependent on the mats of PL-PSPE and ZN-GL-CA, while the antioxidant activity was ascribed to both of them. The distinguishable color changes of PSPE at pH 2–12 endowed the mats with a wide pH–sensing range. Each component of PL-PSPE and ZN-GL-CA were hydrogen bonded. An appropriate presence of GL (no more than 20%) could improve the thermal stability of the fibers. The releases of PSPE and CA from fiber matrix were controlled and followed Fickian diffusion mechanism. In addition to the reversible and high sensitive color change, the mats showed good antibacterial and antioxidant activities, which could extend the shelf life of pork by 24 h at 25 °C. This study demonstrated the great potential of PL-PSPE@ZN-GL-CA in food freshness monitoring and preservation.