Influence of relative humidity and film composition on oxygen and carbon dioxide permeabilities of edible films

At low relative humidity (RH), an edible wheat gluten film presents very low oxygen and carbon dioxide permeabilities [1.24 and 7.4 amol/(Pa m s), respectively, at 25 degrees C]. For higher than 60% RH, O-2 and CO2 permeabilities increase exponentially [to 1290 and 36 700 amol/(Pa m s), respectively, at 95% RH], presumably due to the plasticizing effect of water molecules. Pectin, chitosan, pullulan, and myofibrillar protein films are also very permeable to O-2 and CO2 at high RH. The selectivity ratio (CO2/O-2 permeability) of all films tested at high RH was very high (from 10 to 28) as compared to conventional synthetic films (4 to 6).