POLARITY HOMOGENEITY AND STRUCTURE AFFECT WATER-VAPOR PERMEABILITY OFMODEL EDIBLE FILMS

A continuous gravimetric measurement method was perfected to determine with accuracy the water vapor permeability of edible films. Two subst ances, methylcellulose and paraffin wax, with different physicochemica l properties, were used as films. Factors affecting permeability inclu ded the polarity of film components, the homogeneity or dispersion of material in the film and the structure which depends on the distributi on of paraffin wax in the composite films. The thickness and the Water Vapor Transmission Rate (WVTR) measurement methods resulted in differ ent values for permeability. WVTR increased with hydrophilicity and he terogeneity. Modeling trials concerning water vapor transport indicate d the major influence that structure had on permeability. Wax-laminate d films had a very high barrier efficiency, comparable with that of sy nthetic films.