Biodegradable films used as barriers for gas and vapor transfer in foods

Transference of gases and vapors through whey isolate protein films is stud ied. The formation of films is done by thermal denaturalisation of proteins , by addition of glycerol as plasticizer and by evaporation of the solvent in casting. A cell of two compartments to measure water vapor transference rate (WVTR) and CO2 and C2H4 permeabilities at various relative humidities is described Relative Humidity (HR) is measured in each cell compartment by electric conductivity, a constant Nitrogen flow is kept in one compartment and another of CO2 or C2H4 in the other: Concentration of gases is measure d by gas chromatography after passage through the cell. The permeability ra tio C2H4 / CO2 decreases as the HR increases from 3.97 for HR of 11.3% up t o 0.23 for HR of 94.0%. WVTR is 0.021 g/hour for HR of 75.1% at 25 degrees C.