Biodegradable intelligent film for food preservation and real-time visual detection of food freshness

Intelligent packaging film employing natural polymer as matrix and pH-sensing dye as indicator for freshness detecting has arouse growing interest in recent years. Herein, robust pH-sensitive smart packaging films (CMC/Anth/GO) were fabricated using carboxymethyl cellulose (CMC) as matrix, anthocyanins (Anth) as indicator and graphene oxide (GO) as enhancer. The oxygen and water vapor barrier performances and the tensile strength of the champion film were improved from 56.21 cm3*μm/(m2*d*kPa), 1346.19 g/(m2*24 h) and 13.83 MPa to 27.56 cm3*μm/(m2*d*kPa), 911.03 g/(m2*24 h) and 42.44 MPa, respectively. Due to the electrophilic property of carboxyl groups, the strong interaction between CMC and GO reduced the surface energy of GO and the water contact angle of film was improved from 88.74° to 142.54°. Moreover, the CMC/Anth/GO smart packaging films with excellent biodegradability displayed visually discernible color response to pH buffer solution and volatile NH3 by naked eyes, which was highly correlated with the TVB-N and pH values. The designed CMC/Anth/GO films exhibited potential application as smart packaging film or gas-sensing labels in monitoring and preserving the freshness of proteinic products.