pH-sensitive chitosan/graphene oxide films enriched with red cabbage anthocyanins for visual spoilage detection in...

Sensor-equipped packaging systems represent a promising advancement for monitoring food quality, particularly in perishable protein sources like meat and fish. Smart packaging enables real-time visual assessments of freshness while promoting sustainability through the use of natural materials. In this study, a newly developed chitosan/graphene oxide (CGO) film incorporating red cabbage extract was designed as a pH-responsive freshness sensor for meat. Anthocyanins from the extract enabled visible color changes in response to spoilage-related pH shifts. Chitosan was crosslinked with glutaraldehyde, while graphene oxide (GO) acted as a reinforcing agent, enhancing mechanical properties with an optimal tensile strength of 13.5 MPa. Field Emission Scanning Electron Microscopy revealed a denser film structure due to GO incorporation. Thermal stability improved, as shown by TGA/DSC analysis. The film's hydrophilicity decreased with increasing GO content, evidenced by a rise in contact angle from 66.1° to 86.4°. Antibacterial activity was also enhanced, though biodegradability declined, with a residual mass of 60 % at the highest GO level. In chicken meat application tests, the film changed color from purple to greenish-blue over 48 h at room temperature, confirming its potential as a smart indicator for freshness monitoring in sustainable food packaging.