Polymer additive migration to foods-a direct comparison of experimental data and values calculated from migration models for polypropylene

Abstract

To reduce the amount of compliance testing for food contact polymers the use of migration modelling is under discussion and being evaluated by an EU Commission funded project (Evaluation of Migration Models No. SMT4-CT98-7513). The work reported in this paper was exclusively funded by industry to provide data for the independent evaluation of a diffusion based model using eight different samples of polypropylene (PP) covering the range of polymers specification and five commonly used plastics additives. One hundred and fifty experimental migration data have been obtained in triplicate and used to evaluate a Fickian-based migration model in the prediction of specific migration of five additives into olive oil. All tests were conducted using olive oil, representing the most severe case for fatty foods, with test conditions of 2h at 121°C, 2h at 70°C and 10 days at 40°C, representing short term exposures at high temperatures and room temperature storage. Predicted migration values were calculated using the Piringer ‘Migratest Lite’ model by entering the measured initial concentration of additive in the polymers(Cp,0) in to the equations together with known variables such as additive molecular weight, temperature and exposure time. Where necessary the data generated in this study have been used to update the model. The results indicate the Piringer migration model, using the ‘exact’ calculations of the Migratest Lite program, predicted migration values into olive oil close to, or in excess of, the experimental results for > 97% of the migration values generated in this study. For all measurements, the predicted migration from the Migratest Lite program was greater than 70% of the observed value. This study has identified the possibility that random co-polymers of propylene and ethylene give higher migration than other grades of polypropylenes and could be treated as a separate case. However, further work on more samples of random co-polymers is required to confirm this finding.