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Are PET-bottles suitable also for wine, liqueur and spirts?
Abstract
PET bottles are increasingly used for different fillings like softdrinks, mineral waters and beer. Amongst it's low weight and it's unbreakability PET bottles are distinguish by a high permeability towards oxygen or carbon dioxide as well as by a bad barrier towards moisture. In view of ethanolic fillings the lost of water should have consequences to the ethanol concentration. In this study the permeation rate of water and ethanol through the bottle wall was determined. As expected the experimental results show that the permeation rate of water is significantly higher than the permeation rate of ethanol. This lead to an increase of the ethanol concentration of ethanolic fillings. Particularly for highly concentrated spirits in small PET bottles and high storage temperatures the water permeation is unfavourable. For a 0.21 PET bottle and an initial concentration of 40.0 Vol% the ethanol concentration increase after a storage time of twelve months at 23 °C to 40.9 Vol%. For a 0.51 PET bottle filled with 40 Vol% alcohol the legal tolerance of 0.3 Vol% will be exceeded after a storage time of approximately 130 days at 23 °C. For a 1.01 bottle corresponding approximately 170 days are extrapolated.
Permeation of organic substances through plastic bottles or closures can impair the quality of the filled products. Permeation measuring technology therefore plays an important role in packaging development.
The management of dissolved and headspace gases during bottling and the choice of packaging are both key factors for the shelf-life of wine. Two kinds of 75 cl polyethylene terephthalate (PET) bottles (with or without recycled PET) were compared to glass bottles filled with a rosé wine, closed with the same screwcaps and stored upright at 20°C in light or in the dark. Analytical monitoring (aphrometric pressure, headspace volume, O2, N2, CO2 and SO2) was carried out for 372 days. After the consumption of O2 trapped during bottling, the total O2 content in glass bottles remained stable. A substantial decrease of CO2 and SO2 concentration and an increase of O2 concentration were observed in the PET bottles after 6 months because of the considerable gas permeability of monolayer PET. Light accelerated O2 consumption during the early months. Finally, the kinetic monitoring of partial pressures in gas and liquid phases in bottles showed contrasting behavior of O2 and N2 in comparison with CO2.
Summary The migration of acetaldehyde from polyethyleneterephthalate (PET) under various conditions was analysed by headspace gas chromatography and flame ionisation detection. The residual amounts of new PET bottles were about 6.3 mg/kg with a migration value of 200 µg/1. On studying the migration at different temperatures and times, behaviour curves characteristic of packing materials made from plastics are obtaind. The amount of acetaldehyde diffusing from PET at a temperature of 40° C reached a constant level after 4 days which was about 10% of the residual value of acetaldehyde. On increasing the temperature by 20° C, this level was raised up to 50%. The results of the analysis of acetaldehyde in soft drinks containing carbonic acid show that the migration in fact is not sufficiently high to influence the taste of these soft drinks. A negative effect on the taste may be recognized with mineral waters and soda when they are exposed to higher temperatures (e.g. 40° C or more) over a longer period of time.