POLARITY HOMOGENEITY AND STRUCTURE AFFECT WATER-VAPOR PERMEABILITY OF MODEL EDIBLE FILMS

A continuous gravimetric measurement method was perfected to determine with accuracy the water vapor permeability of edible films. Two substances, methylcellulose and paraffin wax, with different physicochemical properties, were used as films. Factors affecting permeability included the polarity of film components, the homogeneity or dispersion of material in the film and the structure which depends on the distribution of paraffin wax in the composite films. The thickness and the Water Vapor Transmission Rate (WVTR) measurement methods resulted in different values for permeability. WVTR increased with hydrophilicity and heterogeneity. Modeling trials concerning water vapor transport indicated the major influence that structure had on permeability. Wax-laminated films had a very high barrier efficiency, comparable with that of synthetic films.