Physical properties of polyol-plasticized edible films made from sodium caseinate and soluble starch blends

Aqueous blends of sodium caseinate and soluble starch, plasticized with polyols, were prepared by casting or by extrusion and hot pressing. The mechanical, thermal, gas and water permeation properties of these blends were studied after their conditioning at various relative humidities. With increasing plasticizer (water, polyols) content there was a progressive decrease of Tg of the blends. The plasticized blends also showed increased percentage elongation, whereas their flexural modulus and tensile strength exhibited a substantial drop. The gas permeability-temperature plots revealed Arrhenius-type relationships with an inflection in the glass transition temperature region.