Effect of lipid self-association on the microstructure and physical properties of hydroxypropyl-methylcellulose edible films containing fatty acids

The effect of saturated and unsaturated fatty acids on hydroxypropyl-methylcellulose (HPMC) based films was studied. Edible films based on HPMC containing lauric (LA), miristic (MA), palmitic (PA), stearic (SA) and oleic (OA) acids were obtained with 1:0.15 polymer–lipid ratio. The particle size distribution and rheological behaviour of the film-forming emulsions were studied, as well as the cross-section and surface microstructure of dried films. The effect of the film microstructure on its mechanical, optical and water barrier properties was analyzed. Saturated LA, MA and PA formed bigger lipid micellar structures than SA and OA in the HPMC aqueous system, which grew notably during film drying, giving rise to crystallized lipid layers in the films which were not observed for SA and OA. Laminar structures improved the moisture barrier properties, but resulted in more brittle, less stretchable, more opaque and less glossy films, depending on the particle size.