Barrier properties of PLA towards oxygen and aroma compounds

PLA samples having different degree of crystallinity and plasticized with acetyl butyl citrate were prepared by extrusion and thermo-moulding. In order to determine the solubility and diffusion coefficients of ethyl esters vapours into the polymer samples, two approaches were assessed, i) the first one by a microgravimetric method, ii) the second one by a permeability approach using a permeation system including a purge-and-trap injector coupled to GC. The structural change of PLA samples before and after aroma sorption were investigated by differential scanning calorimetry (DSC). In parallel, the oxygen barrier properties were determined. Data were compared to conventional packaging materials. Increasing crystallinity of PLA enhances the barrier properties against ethyl acetate but has no effect on the oxygen permeability. A plasticizing effect was noticed which depends on the hydrophobicity of the ethyl ester. The more hydrophilic compound ethyl acetate is absorbed in high quantities and causes higher plasticization. PLA has, in comparison to polyethylene widely used in food packaging, promising barrier properties especially towards hydrophobic aroma compounds