Barrier properties of biodegradable polyesters towards aroma compounds
Résumé
The capability of two innovative packaging materials, poly(lactic acid), PLA, and poly(hydroxybutyrate), PHB to stabilise the aroma formulation of foodstuff during storage were investigated. Isotherms and solubility coefficients of ethyl acetate (EA) into PLA and PHB were determined using a microgravimetric method. The structural change of the PHB and PLA (with various degrees of crystallinity) films and their rheological behaviour before and after aroma sorption were respectively investigated by differential scanning calorimetry (DSC) and by dynamic mechanical analysis (DMTA). The gas barrier properties were measured through oxygen and helium permeation tests. For PLA, the degree of crystallinity seems to have no effect on gas barrier properties. PHB provides better helium and oxygen barrier properties than PLA. The solubility coefficients of EA are dependent on the film processing and on the activity of the aroma compound, a behaviour largely observed for semi-crystalline polymers. The mass uptakes of EA were the smallest in PHB and the PLA sample which is the most crystalline. It however seems that the high crystalline PHB performs better than PLA at the highest aroma compound activity.