Comparison of flat film to total package water vapour transmission rates for several commercial food wraps

The barrier properties of a package are the sum of material and seal permeations. Although addressed for hermetically sealed and modified atmosphere packages, little consideration of total package permeation has been given to commercial food wraps. Standard protocols were used to compare the water vapour transmission rates (WVTRs) of materials and packages for seven commercial food wraps: aluminum foil; poly(vinylidene chloride) (PVdC) film; three poly(ethylene) (PE) films; an adhesive-modified PE film; and plasticized poly(vinyl chloride) (PVC) film. Water ingress for a complete package was compared to calculated material permeation based on film WVTRs. Film-to-glass adhesion strength was also measured. Model systems (desiccant) were compared to foods at ambient and refrigeration temperatures. Aluminum foil had the lowest material WVTR (0.10 g/h/m(2)) closely followed by PVdC (0.13 g/h/m(2)). These WVTRs were approximately five-fold lower than the PEs (similar to0.65 g/h/m(2)), which were nearly 10-fold lower than PVC (4.9 g/h/m(2)). The adhesive-modified PE film had the lowest difference between material and package transmission rates (0.7 E-03 g/h), approximately half that of the PVdC film (1.1 E-03 g/h), which was significantly lower than the remaining films (2.3 E-03 -3.9 E-03 g/h). The adhesive PE film had the strongest film-glass adhesion. Ambient food product test results were similar to model system (desiccant) results, but refrigerated trials showed significantly different relative package transmission rates. This was attributed to the reduced adhesion Of most wraps at refrigeration temperatures. Copyright (C) 2002 John Wiley Sons, Ltd.