Materials and articles intended to come into contact with food must be shown to be safe because they might interact with food during processing, storage and the transportation of foodstuffs. Framework Directive 89/109/EEC and its related specific Directives provide this safety basis for the protection of the consumer against inadmissible chemical contamination from food-contact materials. Recently, the European Commission charged an international group of experts to demonstrate that migration modelling can be regarded as a valid and reliable tool to calculate 'reasonable worst-case' migration rates from the most important food-contact plastics into the European Union official food simulants. The paper summarizes the main steps followed to build up and validate a migration estimation model that can be used, for a series of plastic food-contact materials and migrants, for regulatory purposes. Analytical solutions of the diffusion equation in conjunction with an 'upper limit' equation for the migrant diffusion coefficient, D P , and the use of 'worst case' partitioning coefficients K P,F were used in the migration model. The results obtained were then validated, at a confidence level of 95%, by comparison with the available experimental evidence. The successful accomplishment of the goals of this project is reflected by the fact that in Directive 2002/72/EC, the European Commission included the mathematical modelling as an alternative tool to determine migration rates for compliance purposes.
The current potential for the use of migration modelling for studying polyolefin packaging materials (low- and high-density polyethylene and polypropylene) is summarized and demonstrated with practical examples. For these polymers, an upper limit of migration into foodstuffs can be predicted with a high degree of statistical confidence. The only analytical information needed for modelling in such cases is the initial concentration of the migrant in the polymer matrix. For polyolefins of unknown origin or newly developed materials with new properties, a quick experimental method is described for obtaining the characteristic matrix parameter needed for migration modelling. For easy handling of both the experimental results and the diffusion model, user-friendly software has been developed. An additional aim of the described method is the determination of the migrant partition between polymer and food or food simulant and the specific contribution of the migrant molecular structure on the diffusion coefficient. For migration modelling of packaging materials with multilayer structures, a numerical solution of the diffusion equation is described. This procedure has been also applied for modelling the migration into solid or high viscous foodstuffs.
Results of experiments, conducted by different polycarbonate (PC) producing companies, on migration of bisphenol A (BPA) from PC into different liquids, were supplied to the author for compilation, review, and discussion. The observed BPA migration levels were found to be nearly independent of the concentration of residual BPA in the PC resins. Hydrolysis of PC is the dominant mechanism responsible for the release of BPA from the polymer surface into the contacting aqueous liquid. Experiments with PC spiked with deuterated BPA revealed that diffusion‐controlled migration play a minor role in the overall release of BPA from PC. The influence of a number of experimental parameters on the migration of BPA into aqueous liquids was studied. Factors found to be of importance included the temperature, pH, and ozone concentration of the liquids, as well as the surface ageing of the PC. All of the BPA migration levels obtained from experiments performed under standard conditions as given in the EU legislation and its associated guidance documents were found to be well below the EU specific migration limit of 600 μg/kg food which applies to plastics in contact with foodstuffs (EU Directive 2002/72/EC as amended). Migration is lower in oil than in the aqueous food‐simulants water, 3% acetic acid, and 10 or 50% ethanol. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Hotmelt adhesives are widely used in the manufacture of multilayer laminates, commonly used as food packaging materials. For this reason, it is very important to determine the composition of the adhesives and to identify which compounds could migrate from the laminate to the food. Twenty four compounds were identified in 2 different hotmelt adhesives, some of them with high toxicity levels according to theoretical model of Cramer, such as 9,10-dihydroanthracene and retene. Some physicochemical properties of these compounds, such as their partition and diffusion coefficients in the different materials used in the laminates, provide useful information for evaluating their potential migration to the food. The determination of the partition and diffusion coefficients was performed with two different laminates made of cardboard or polypropylene cardboard substrates and the adhesive. Partition and diffusion coefficients of the migrants in the adhesives and substrates were calculated from the experimental results. It was found that diffusion was always lower in the adhesive than in the cardboard. All diffusion coefficients determined increased with temperature while the partition coefficients showed the opposite effect. Migration results confirmed that the migration value of a compound was closely related to the calculated partition and diffusion coefficients. None of the migrants exceeded the recommended Cramer exposure values.
A wide variety of adhesives can be used to manufacture multilayer food packaging materials. Since these materials are usually in direct contact with the packed food, compounds from the adhesive may migrate into it. Therefore it is important to determine the composition of the adhesives used. The main aims of this work were to determine the compounds present in the adhesives used in the food packaging, to study their migration to food simulants and finally to use these data to test a mathematical tool designed for predicting migration to food from laminates containing adhesives. For this purpose a total of 45 market samples of multilayer materials (laminates and other glued materials) produced with 29 different adhesives were studied. A total of 55 different compounds were detected in these adhesives, 57% of these compounds migrated into a dry food simulant (Tenax®) through the food contact layer. These data were also used to compare it with the theoretically estimated migration of the adhesive compounds using "upper-bound reference" values for the diffusion and partition coefficients implied in a multilayer migration model. In 93% of the cases the estimated migration results met or exceeded the experimental ones. This is an important requirement for testing the applicability of these theoretical migration estimations for compliance decisions which aim to protect the consumer's health
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