Resistance of lipid films to transmission of water vapor and oxygen.

Various lipids, present as thin films on polar filter paper supports, were evaluated for resistance to the transmission of water vapor (rH2O) and oxygen (rO2). Beeswax exhibited the largest r(H2O), followed in order by fully-hydrogenated soy-rapeseed oil, stearyl alcohol, acetylated monoglycerides, hexatriacontane, tristearin, and stearic acid. Most of the lipids exhibited negative activation energies, E, for resistance to transmission of water vapor and positive Es for resistance to transmission of oxygen. The type of lipid support (hydrophobic or hydrophilic) also influenced E for resistance to water vapor transmission. Differences in r(H2O) for the various lipids, comparative r(H2O) and r(O2) values, and the temperature dependence of these values can be explained, in part, by the degree of hydrophilicity of the lipid molecule. Tempering at 48 degrees C of stearyl alcohol caused a substantial decrease in its permeability to oxygen and water vapor. The polymorphic form of a blend of fully-hydrogenated soybean and rapeseed oil had a moderate influence on its permeability to oxygen and water vapor. This information will be useful for formulating lipid-containing films with controlled barrier properties to the passage of water vapor and oxygen.