Properties of edible sodium caseinate films and their application as food wrapping

Sodium caseinate solutions (2.5g protein/100g solution) containing glycerol (gly) at gly:protein ratios of 0, 0.08, 0.16, 0.24 or 0.32 w/w were dried over 48h at 50±5% RH and 23±2°C to form transparent flexible films of approximately 35μm thickness. Maximum load, tensile strength and elastic modulus of films decreased and the moisture content increased significantly with increasing glycerol content. Elongation and water vapour permeability of films increased significantly only at gly:protein ratios of 0.24 and 0.32. Wrapping bread samples in the caseinate films reduced hardness during 6h storage at ambient temperatures relative to unwrapped controls. However, the caseinate films were not as effective in this regard as synthetic polyvinyl chloride film.