Abstract: Protein-polysaccharide coaggregation based on electrostatic interactions (ionic bond and van der Waals force) has potential application for improving the performance of edible films. The effect of addition of different amounts of carboxymethyl cellulose (CMC) (with negative charges) on the properties of acid-swollen collagen fiber (with positive charges)-based films was investigated in this study. The results showed that the film-forming suspension began to aggregate and even could not form a film with the addition of excessive CMC (more than 10%, on the basis of collagen fiber mass). The ζ-potential value of the film-forming suspension decreased significantly with the increase in CMC concentration (0%–5.0%); however, no obvious change was observed in pH. At the same time, scanning electron microscopic (SEM) images showed that the film microstructure became rougher, the film thickness was increased and consequently the light transmittance was decreased significantly (P < 0.05) with the increase in CMC concentration. Moreover, the tensile strength and Young’ modulus of the composite films significantly increased with increasing CMC concentration (P < 0.05), while the extension at break decreased significantly (P < 0.05). The water vapor permeability of the composite film containing 5.0% CMC was (32.41 ± 0.86) g/(m·s·Pa) and its oxygen barrier property and swelling kinetics were improved significantly as compared to the control (P < 0.05). Additionally, differential scanning calorimeter (DSC) analysis indicated the incorporation of CMC improved the thermal stability of the composite film. It can be concluded that CMC could combine with collagen fiber by electrostatic interaction when added to the film-forming suspension, thereby improving the mechanical strength and barrier properties of the resulting film. The combination of CMC and collagen fiber provides a powerful tool for improving the properties of edible films.

Key words: collagen fiber film, carboxymethyl cellulose, mechanical properties, composite film