Effect of concentration and relative humidity on the transfer of alkan-2-ones through paper coated with wheat gluten

The transport properties of two methyl ketones, 2-heptanone and 2-nonanone, through a paper coated with a wheat gluten (WG) solution were studied as a function of aroma compound concentration differential and relative humidity. Whatever the conditions, coating improved the aroma barrier properties of the paper. Whereas permeability of 2-nonanone through WG coated paper was not affected by the concentration differential, a high concentration of 2-heptanone induced a permeability increase, which can be explained by a slight plasticization effect of this compound. The moisture content of the films markedly affected the barrier properties depending on the aroma compound. For 2-heptanone, the most polar compound, the increase of permeability with relative humidity was related to the increase of diffusivity and solubility coefficient of this compound. With 2-nonanone, permeability and diffusivity coefficients strongly decreased with the increase of moisture content. This decrease could be linked to the hindrance in diffusivity of the less polar compound induced by the presence of water molecules. The different behavior in permeation properties seems to be related to the hydrophobic nature of the aroma compound. At intermediate and high humidity levels, coated papers are found to have better aroma barrier properties than LDPE films.