Morphological, mechanical and physical properties of new whey protein isolate/polyvinyl alcohol blends for food flexible packaging

Attempting to make whey protein isolate (WPI)-based films more suitable for application as food packaging, it is necessary to improve its brittleness, water barrier and solubility in water, for example, by adding another polymer to its matrix. This work objectives to understand the interactional phenomena between WPI and polyvinyl alcohol (PVOH) and to evaluate the effect of the addition of up to 30% of PVOH on flexibility, water vapor barrier and solubility in water of WPI films. FT-IR analysis of the blends showed the formation of new interactions and structures, while morphology analysis indicated a possible compatibility between the polymers. The addition of 30% of PVOH provided a more ductile material, increasing nine times the WPI elongation capability, leading to tensile properties close to that from commercial LPDE. PVOH addition did not act reducing puncture resistance or water barrier, but decreased solubility of WPI film in water. It is indicated the addition of 30% of PVOH in WPI matrix in order to improve its flexibility and reduce solubility in water.