Migration Testing of Polyethylene Terephthalate: Comparison of Regulated Test Conditions with Migration into Real Food at the End of Shelf Life

Abstract

Polyethylene terephthalate (PET) in contact with food must comply with the requirements laid down in the European Regulation (EU) 10/2011, which specifies conditions for migration tests. For real contact times longer than 30 days, accelerated migration tests are performed at elevated temperatures for a maximum of 10 days at 60°C. These conditions should represent the end of the shelf life (e.g. 365 days at 23°C) and are calculated using the Arrhenius equation on the basis of a default activation energy of 80 kJ/mol. However, for PET, it is well known that the activation energy is strongly dependent on the molecular size of the migrant. Small molecules like acetaldehyde have activation energies in PET of ~80 kJ/mol. For larger molecules like 2‐aminobenzamide with a predicted activation energy of diffusion of 134.4 kJ/mol, the storage times at 60°C and 40°C equivalent to the migration after 1 year at 23°C are 0.85 and 18.9 days, respectively. These findings were confirmed by experimental migration tests. For 2‐aminobenzamide, migration for 10 days at 60°C corresponded to a storage time at 23°C of 11.7 years, which is significantly higher than the long‐term storage of more than 6 months as foreseen in Regulation (EU) 10/2011. For larger molecules, the corresponding storage times at 23°C would even be longer, thus overestimating by far the migration at the end of shelf life. Contact conditions of 10 days at 60°C are too severe for PET. Migrant‐specific and polymer‐specific diffusion parameters should therefore be considered when designing accelerated migration tests for long‐term applications. Copyright © 2017 John Wiley & Sons, Ltd.

Migration from acrylonitrile butadiene styrene (ABS) polymer: swelling effect of food simulants compared to real foods

“…Contact conditions of 10 days at 60 °C and 40 °C with 50% or 95% ethanol are too severe for ABS compared to real food and anticipated storage conditions. These findings are in agreement with previously reported results for other polymers, such as for styrene-acrylonitrile copolymer (SAN) (Yoshida et al 1982) and polyethylene terephthalate (PET) (Franz et al 2016;Gehring and Welle 2018).…”

Diffusion Coefficients and Activation Energies of Diffusion of Organic Molecules in Polystyrene below and above Glass Transition Temperature

“…A similar behavior is reported for acrylonitrile butadiene copolymer (ABS) [33]. Interaction between the polymer and the food simulants mainly influences the migration into food, which was also reported for PET [34]. However, real food does not swell the packaging polymer significantly, especially at low temperatures, otherwise packaging polymer might be unsuitable for this purpose.…”

“…However, for convenience and as specified in regulatory guidelines, food compliance testing is typically performed with simulants like 50% ethanol or iso-octane. This leads to a strong over-estimation of the level of migration [33,34]. In addition, sorption and swelling had an influence also on the diffusion coefficients determined in PS.…”

Migration of Bisphenol A from Can Coatings into Beverages at the End of Shelf Life Compared to Regulated Test Conditions

“…However, it should also be noted that in none of the performed overestimative migration tests was the specific migration limit of bisphenol A of 50 µ g/L, according to Regulation (EU) No 10/2011, exceeded. The migration potential of bisphenol A in the can coating, which assumes a complete transfer of bisphenol A into the beverage, was only 10.2 µ g/L (sample 1) and 5.3 It has also been observed for polyethylene terephthalate (PET) materials that ethanolic food simulants lead to an increased migration due to swelling effects [2,9,10]. Similar effects are expected to have occurred in the investigated epoxy resins.…”

“…On the other hand, it is known that ethanolic solutions show strong interactions between polyester materials like epoxy can coatings. These interactions result in a swelling of the polyester matrix which significantly increases the extent of migration, especially if the migration test is performed at elevated temperature [2]. This increased migration is part of the safety concept, that ethanolic solutions act as worst-case simulants compared to real beverages, which results in a safety factor.…”