Rapid and Facile Synthesis of Homoporous Colorimetric Films Using Leaf Vein-Mediated Emulsion Evaporation Method for Visual Monitoring of Food Freshness

A new method for rapid and facile fabrication of homoporous films with high volatile amine sensitivity was developed. First, red cabbage anthocyanin was encapsulated in ethyl cellulose to form water-in-organic (W/O) emulsion. Afterward, the W/O emulsion was rapidly dried using the supporting matrix Magnolia Grandiflora Linn leaf vein at 60% relative humidity and 50 °C to form a colorimetric film with regular hexagonal pores with an average side length of about 23 μm. The films exhibited good sensitivity to ammonia (NH3), dimethylamine, and trimethylamine, with limit of detection of 0.26, 0.24, and 0.38 μM, respectively, and high stability when stored in high humid environments. An obvious color change of the films from pink to green was clearly observed during the freshness monitoring of pork, chicken, salmon, and shrimp. Thus, this work offered a novel and reliable method for the development of porous films for food freshness monitoring.