Intelligent and active films with thymol and red cabbage anthocyanin for advanced fish packaging

The objective of this study was to produce new active and intelligent high performance colorimetric films based on cellulose acetate (CA), and to evaluate the synergistic effect of thymol (THY) and anthocyanin (ANT). The colour films showed significant reactivity to pH change, and the films became thicker in the presence of glycerol (0.200 ± 0.05). FTIR and SEM images showed a homogeneous distribution and new interactions created between THY, ANT and CA, which modified the thermal properties. This behaviour was also confirmed by XRD analysis, which showed a reduction in film crystallinity with increasing anthocyanin concentration. In addition, the incorporation of ANT improved the mechanical properties by reducing the tensile strength (0.075 ± 0.021 MPa), the biodegradability of the films in the soil after 60 days and also the water vapor transmission rate (14.81 g mm^-2 h^-1). The films showed synergistic antibacterial activity and the application trials showed colour changes that were highly visible to the naked eye, with the deterioration of the fish, suggesting a promising application for these films as an indicator of fish freshness.