Modelling transport between a monolayer and a bi-layer polymeric package and food.

There is considerable interest in the recycling of food packaging, but also the potential for problems. Any chemical component initially located in the re-used food packaging may be responsible for contamination of the food. The kinetics of this transfer can be established whether the food is liquid or solid. The process is controlled by diffusion in the packaging and by convection in the liquid food or by diffusion in the solid food. A bi-layer package made of a re-used polymer layer and a virgin polymer layer exhibits quite different kinetics for the contamination of the food. The role of the virgin polymer layer or so-called functional barrier can be established either by the kinetics of contaminant transfer or by the profiles of concentration developed through the packaging-food system. Dimensionless numbers are used in order to be of help to anyone in need of precise information on the length of time this functional barrier offers protection of the food.