Food law compliance of poly(ethylene terephthalate) (PET) food packaging materials

Poly(ethylene terephthalate) (PET) is widely used as a packaging material for all kinds of foodstuff. Low diffusivity of the polymer combined with the limited number of additives and their low concentrations lead to very limited mass transfer (migration) of monomers, catalysts, or impurities from the PET polymer into food. This mass transfer (migration) for monomers, oligomers, catalysts, additives and non-intentionally added substances (NIAS) is discussed within this study. Based on the data given in the scientific literature it could be concluded that overall migration tests as well as specific migration tests for monomers and catalysts, like ethylene glycol, diethylene glycol, terephthalic acid, iso-phthalic acid and antimony are superfluous, because their migration limits cannot be exceeded, even if worst case conditions and swelling simulants like 95% ethanol are applied. A more suitable procedure for evaluation of the food law compliance of PET is the determination of migration relevant substances in PET and calculation of their migration by use of migration models. In addition, the analytical screening for low molecular weight migrants (like NIAS) gives an additional safety factor, because such NIAS were not determined using the conventional migration testing procedures.