Edible films made from hydroxypropyl starch and gelatin and plasticized by polyols and water

Two methods, known as the low and the high temperature methods, which consist of casting aqueous solutions of hydroxypropyl starch and gelatin at 20 and 60 degrees C, respectively, were employed for film preparation. The physical (thermal, mechanical and gas/water permeation) properties of these composite films, plasticized with water or polyols, were studied. An increase in the total plasticizer content resulted in a considerable decrease in elasticity modulus and tensile strength (up to 60% of the original values when 25% plasticizer was added), whereas the percentage elongation increased (up to 200% compared to the original values). The low temperature method led to the development of higher percentage renaturation (crystallinity) of gelatin which resulted in a decrease, by one or two magnitude orders, of CO2 and O-2 permeability in the hydroxypropyl starch/gelatin bleeds. An increase in the total plasticizer content (water, polyols) of these blends was found to be proportional to an increase in their gas permeability. (C) 1998 Elsevier Science Ltd. All rights reserved.