Ethyl hexanoate transfer in paper and plastic food packaging by sorption and permeation experiments

The barrier properties of one treated paper packaging and one standard plastic film (bi-oriented polypropylene, biOPP) were assessed for ethyl hexanoate. Three methods based either on sorption (gravimetry and micro-atmosphere-derived method) or permeation kinetic determination were used in controlled conditions of aroma vapor concentration (107 Pa), temperature (25 °C) and relative humidity (about 0 %). Ethyl hexanoate solubility values were on the same range of magnitude for both packaging films in spite of their different nature and composition. Ethyl hexanoate affinity for both films was well predicted by their respective solubility parameters. Solubility values were different according to the experimental method used. The micro-atmosphere-derived method and the permeation method both presented experimental limitations for the solubility determination. Ethyl hexanoate diffusivity values were significantly different between the three methods used. Particularly, the values were 10-folds higher by the permeation method than by the sorption methods for the treated paper. Whatever the method, ethyl hexanoate diffusivity was always higher through the treated paper than through the biOPP. Ethyl hexanoate permeability was controlled by diffusivity for both films and probably linked to the evolution of the film structure during transfer. Permeability could thus not be calculated from the product of diffusivity and solubility coefficients.