Food Packaging and Preservation

The materials used in food packaging are very often common polymers. Their permeability to gases and vapours is at the origin of their barrier properties and capacity for protection of the food. The permeability coefficient, which is at thermodynamic equilibrium equal to the product of diffusivity and solubility, depends on the structure of the polymer as well as the properties of diffusing molecules. Polymer properties affecting permeability, such as free volume, crystallinity, tacticity, cross-linking, orientation and thickness, are reviewed as well as permeant characteristics, size and shape and polarity, especially for water vapour, which are described in relation to their influence on permeability. Different experimental methods of determination ...of permeability are also summarized.