The improvement of characteristics of biodegradable films made from kefiran–whey protein by nanoparticle incorporation

• New bionanocomposite films were developed based on kefiran–WPI.
• MMT and TiO2 nanoparticles content had great effect on the properties of films.
• MMT improved the physico-mechanical and barrier properties.
• A significant change in the optical attributes by adding TiO2 was found.
• TiO2 had a quasi-placticizing role for kefiran–WPI films.

Biodegradable kefiran–whey protein isolate (WPI) nanocomposites were produced using montmorillonite (MMT) and nano-TiO2 as nanoparticles in the percentage of 1, 3, and 5% (w/w) by a casting and solvent-evaporation method. Physical, mechanical, and water-vapor permeability (WVP) properties were determined as a function of nanoparticle concentration. The results revealed that the effect of these nanoparticles was different according to their nature and percentage. The films incorporated with 5% (w/w) MMT showed the highest tensile strength, Young's modulus, puncture strength, and the lowest WVP compared with the control and TiO2 added films. In contrast to MMT, addition of TiO2 nanoparticles due to the plasticizing effect led to a significant change in color and transparency of nanocomposite. Scanning electron microscopy (SEM) observations demonstrated the films’ properties in relation to their microstructures. The surface topography results also showed a considerable increase in roughness parameters by incorporating the nanoparticles in kefiran–WPI matrix.