Rheological, physicochemical, and structural properties of fish gelatin/carboxymethyl cellulose/Persian gum ternary edible films

Abstract This study explored the modulation of fish gelatin (FG)/carboxymethyl cellulose (CMC) edible films using Persian gum (PG), focusing on structure-rheology-function relationships and physicochemical performance. Ternary FG/CMC/PG films with mass ratios of 60/40/0, 54/36/10, 48/32/20, 42/28/30, and 36/24/40 were prepared by solution casting. Rheological analysis of film-forming solutions revealed shear-thinning behavior across all formulations, with 10% PG increasing viscosity, possibly because of favorable polymer associations and entanglements, whereas higher PG concentrations (20–40%) decreased viscosity, possibly reflecting concentration-dependent network rearrangement and increasing heterogeneity. Dynamic oscillatory measurements showed that incorporation of PG shifted the viscoelastic response toward a more elastic, solid-like network, suggesting enhanced interactions between PG and FG/CMC chains. Mechanical testing indicated that increasing PG content decreased tensile strength and elongation-at-break, while water vapor permeability increased from 0.74 to 0.95 g mm/kPa h m 2 , and solubility decreased by up to 41% relative to the control, reflecting changes in polymer interactions and film structure. Optical analyses demonstrated that PG improved film transparency. Structural characterization through Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), and differential scanning calorimetry (DSC) analyses provided evidence of intermolecular interactions and compositional effects on molecular organization, while SEM and AFM observations revealed increasing morphological heterogeneity at higher PG concentrations, suggesting possible microphase separation. Overall, the FG/CMC/PG ternary films developed in this study exhibited tunable functional properties and demonstrated the potential of Persian gum as a natural modifier for developing biodegradable films with potential suitability for food-packaging applications.