Chitosan and gelatin based edible films: state diagrams, mechanical and permeation properties

Films of chitosan and gelatin were prepared by casting their aqueous solutions (pH approximate to 4.0) at 60 degrees C and evaporating at 22 or 60 degrees C (low- and high-temperature methods, respectively). 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 of elasticity modulus and tensile strength (up to 50% of the original values when 30% plasticizer was added), whereas the percentage elongation increased (up to 150% compared to the original values). The low-temperature preparation method led to the development of a higher percentage renaturation (crystallinity) of gelatin which resulted in a decrease, by one or two orders of magnitude, of CO2 and O-2 permeability in the chitosan/gelatin blends. 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.