Mono-component and composite bilayer and blend films composed of chitosan and whey
protein were made. Colour, microstructure, water contact angles, swelling, water vapour
sorption, barrier properties (oxygen, water vapour), water vapour diffusion coefficients and
mechanical properties were determined. The influence of water vapour on barrier properties
was studied in relation to the surface and structural properties. Mono-component and
bilayer films were transparent with a homogeneous surface. Contrarily, blend films were
translucent. Bilayer films had significantly lower water vapour permeability in comparison
to mono-component and blend films. In all bilayer films, the air side (chitosan) was
characterized by swelling, while the support side (whey protein) swelled after initial
absorption. At low relative humidities, blend films were excellent barrier to oxygen and
they completely lost their gas barrier performance in a humid environment. Bilayer films
had enhanced mechanical resistance. The films with higher chitosan content showed
higher capacity for elongation. Lamination and blending of chitosan and whey protein is
a useful method to obtain new materials with desired functional properties.