The objectives of this study were to demonstrate that the presence of ethanol in a solution containing two esters and two aromatic alcohols has several consequences on the sorption of these compounds into polyethylene (PE) film. First, sorption of ethanol into the PE film occurred at the same time as water and reached 8 kg m(-3) using 12% v/v of ethanol. This sorption was associated with an increase in PE crystallinity, which may have prevented the sorption of volatile compounds despite their strong affinity with PE film, as evaluated by Hansen solubility parameters. Moreover, increasing the ethanol concentration increased the solubility of the four volatile compounds. In the case of aromatic alcohols, the sorption was decreased in the presence of ethanol as expected. In the case of esters, as their hydrolysis was substantial in the presence of water, the consequence was a higher sorption into the PE film in the presence of ethanol than in its absence. Nevertheless, the sorption also depended on the concentration of ethanol and the heterogeneity of the ethanol-water mixture as well as the presence of other volatile compounds, as in the case of 4-ethylphenol. In conditions simulating wine packaging, losses of volatile compound by sorption and by permeation estimated after only 5 days of contact varied between 0.08 and 25% for 2-phenylethanol and ethyl hexanoate, respectively.
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.
Keywords: Wheat gluten; coated paper; aroma compounds; transfer; relative humidity
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