Rheological and structural characterisation of film-forming solutions and biodegradable edible film made from kefiran as affected by various plasticizer types

The rheological properties of kefiran film-forming solutions, as well as the structural characterisation of the resulting films, were investigated as a function of various plasticizer types. The behaviours of the storage (G′) and loss (G″) moduli as a function of frequency were typical of gel-like material, with the G′ higher than the G″. Kefiran-based films, which may find application as edible films, were prepared by a casting and solvent-evaporation method. Possible interaction between the adjacent chains in the kefiran polymer and various plasticizers was proven by Fourier-transform infrared spectroscopy (FT-IR). The crystallinity of plasticized kefiran film was also analysed using X-ray diffraction (XRD); this revealed an amorphous-crystalline structure. These results were explained by the film's microstructure, which was analysed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The present study has helped determine possible interactions of kefiran, plasticizer and water molecules in determining film properties.