Modelling permeation through porous polymeric films for modified atmosphere packaging

The use of perforated packaging films is increasing with the application of modified atmosphere packaging for fresh produce. These films provide high to very high mass exchange rates. However, irrespective of the chemistry of the material, mass transport through such films cannot be described using conventional permeability equations (Henry's plus Fick's laws). Other expressions such as Knudsen's law, gas diffusivities or Poiseuille's hydrodynamic flow can be applicable. The application of these laws is discussed and their corresponding range of validity is provided. These laws were also applied to model experimental permeation rates of oxygen and water and were further used to describe the headspace evolution of two fruit products in modified atmosphere packaging. In the light of these results, the contribution of different factors to the headspace evolution is discussed.