The behaviour of wine aroma compounds related to structure and barrier properties of virgin, recycled and active PET membranes

Virgin PET, 100% recycled PET and PET containing an oxygen scavenger have been compared for their thermal properties and gas and aroma compound permeability. Thermal properties were slightly different between virgin and recycled PET, which exhibited the same degree of crystallinity but also strong heterogeneity in dispersion and size of crystals. However, glass transition was higher in the presence of oxygen scavenger because of its nature. Similar oxygen and carbon dioxide permeability were measured for virgin, recycled and PET with 1% of oxygen scavenger, whereas with 3% of oxygen scavenger gas barrier properties increased. Water barrier properties of PET were not influenced either by recycling or by the presence of oxygen scavenger and a plasticization effect was evidenced for all films. Concerning volatile organic compounds such as ethanol and aroma compounds, virgin PET was the best barrier. Permeability was strongly affected by the affinity of the compound for the material. Sorption of pure or diluted solution of ethanol induced changes in thermal properties with a slight decrease in Tg and a marked decrease of crystallinity. In contrast, the oxygen permeability after contact with the diluted solution of ethanol was increased, suggesting a reduction of free volume by sorption. Finally, the impact of film barrier properties on three aroma compounds of wine was evaluated and confirmed the inertness of PET concerning aroma compounds and the positive effect of active packaging.