The total perforation area is not the only factor controlling the permeability of miroperforated packages

The use of laser perforation systems has expanded the applicability of modified atmosphere packaging, allowing for higher carbon dioxide concentrations. Different theoretical approaches have been proposed in literature, and some assumptions used and conclusions reached are not actually supported by a careful analysis of the data that has been reported. The quantification of the gas exchange through perforated packages for oxygen and carbon dioxide is addressed in this work by pooling published data and reviewing methods that have been proposed to date. It is shown that the effective permeability of a perforated package is approximately what would be expected from chemical engineering dimensionless correlations for mass transfer from flat planes for perforation diameters of around 1 mm and bigger, which makes other methods of analysis rather redundant. However, for smaller perforations the effective permeability increases significantly with decreasing diameters, which proves that the total perforation area is not the only factor controlling the permeability of perforated packages, and this is particularly crucial for microperforations. The concentration gradient across the package is also found to be relevant. An engineering design analysis proves that even small differences in values of mass transfer coefficients have a dramatic effect on the result, and also show that the diffusion coefficients that need to be used should refer to the specific case of multicomponent diffusion with high carbon dioxide contents, and not diffusivities across otherwise stagnated air.Original title, authors and sourcesANALYSIS OF THE PERMEABILITY OF MICROPERFORATED PACKAGING FILMSOliveira, J.C.(*) and Sousa - Gallagher, M.J.JMFCOliveira@gmail.comDpt. Process & Chemical Engineering, University College Cork, Ireland CA MA 2013, XI International Controlled & Modified Atmosphere Research Conference, Trani (Italy), 3-7 June 2013