Parameters Affecting the Water Vapour Permeability of Gelatin Films as Evaluated by the Infrared Detecting Method ASTM F1249

Abstract

The purpose of this study was to assess testing parameters for measurement of water vapour permeability (WVP) properties of bovine gelatin films by ASTM F1249. This method utilises an infrared sensor to determine the WVP of conventional plastic-based films and has been widely applied within the packaging industry, but has had very limited application with hydrophilic compostable/edible packaging materials. These films have low WVP properties with highly variable WVP values (as studied by ASTM E96); consequently, this parameter has to be carefully controlled. Assessment of the module was carried out using bovine gelatin films with different thicknesses of film, and gelatin was chosen as an example of such film types using the following Mocon Permatran testing parameters: 50 or 70% relative humidity (RH), 100 or 150 cm3 nitrogen gas flow rates for the module’s RH-cell (100 cm3 for all other cells). In all cases, WVP increased with an increase in gas flow rate. This method showed that WVP increased with increasing gelatin film thickness, and categorically supports previous—and often unexplained—WVP findings for other hydrophilic, biopolymer films. The current study is a helpful guide to the examination of water barrier properties of hydrophilic edible/biodegradable/compostable packaging materials in research and industry.