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- Analysis of mathematical models to describe the migration of additives from packaging plastics to foodsPublication . Poças, Maria F.; Oliveira, Jorge C.; Brandsch, Rainer; Hogg, TimothyThe mathematical modeling of migration of additives from plastics to food simulants was studied using experimental data published in the literature, following two routes: the conventional approach using the solution of Fick’s 2nd law, and a kinetic model based on the Weibull distribution function. The objective of this comparison was to permit using a mathematically simpler model equally able to describe migration data, and that could have a generally wider applicability by describing situations more complex than those that simple diffusional phenomena can describe. The relationship between the parameters of the two models was analyzed by regression of data generated by Fick’s law using the Weibull model. The results show that the time constant parameter is related to the diffusion coefficient and the material thickness.It depends on temperature and on the molecular weight of the migrant in a similar manner to the diffusion coefficient. The activation energy presented values from 72 to 125 kJ/mol. The shape parameter is a function of the contribution of the mass transfer resistance at the interface. It was independent of temperature and of the migrant, assuming a global constant value of 0.67, for the systems and conditions studied. The results indicate that the Weibull model can be used to describe and analyze the migration of additives from plastics to foods with a meaning of the parameters in terms of the underlying physical phenomena.
- Modelling migration from paper into a food simulantPublication . Poças, Maria de Fátima; Oliveira, Jorge C.; Pereira, Joel R.; Brandsch, Rainer; Hogg, TimThe migration of components from paper into Tenax (R) was studied to determine the influence of molecular size and chemical character of the migrant and the influence of paper characteristics in the migration process The Weibull model was applied because Fick s 2nd law of diffusion gave poor fits in some cases The migration pattern depended on the migrants molecular size and was independent of temperature in the studied range The migration rate decreased with the migrant molecular size The influence of the migrants character (polarity and vapour pressure) on the migration behaviour was also studied nonpolar migrants with high vapour pressure presented low relative migration values and polar migrants presented high values of relative migration Results indicated that the apparent partition coefficient between paper and the simulant Tenax (R) increased with the migrant vapour pressure and with both the paper grammage and the recycled pulp content
- Feasibility study on the use of probabilistic migration modeling in support of exposure assessment from food contact materialsPublication . Poças, Maria F.; Oliveira, Jorge C.; Brandsch, Rainer; Hogg, TimThe use of probabilistic approaches in exposure assessments of contaminants migrating from food packages is of increasing interest but the lack of concentration or migration data is often referred as a limitation. Data accounting for the variability and uncertainty that can be expected in migration, for example, due to heterogeneity in the packaging system, variation of the temperature along the distribution chain, and different time of consumption of each individual package, are required for probabilistic analysis. The objective of this work was to characterize quantitatively the uncertainty and variability in estimates of migration. AMonte Carlo simulation was applied to a typical solution of the Fick’s law with given variability in the input parameters. The analysis was performed based on experimental data of a model system (migration of Irgafos 168 from polyethylene into isooctane) and illustrates how important sources of variability and uncertainty can be identified in order to refine analyses. For long migration times and controlled conditions of temperature the affinity of the migrant to the food can be the major factor determining the variability in the migration values (more than 70% of variance). In situations where both the time of consumption and temperature can vary, these factors can be responsible, respectively, for more than 60% and 20% of the variance in the migration estimates. The approach presented can be used with databases from consumption surveys to yield a true probabilistic estimate of exposure.