FOOD CONTACT MATERIALS - MATHEMATICAL MODELLING OF MIGRATION
Mathematical modelling of additive or monomer diffusion, particularly in multi-layer materials, can support the understanding of migration processes and help in demonstrating suitability and safety in different food-contact situations. Mathematical algorithms/methods can be used to quantify the diffusion of a substance within a multi-layer material and its migration from the material into a contacting material or medium. Compliance with the Plastics Directive 2002/72/EC can in many cases be demonstrated using modelling software, with significant cost savings over standard analytical testing. The approach can also be used to examine migration into food from packaging "set-off".
Some examples of the use of mathematical modelling are shown below.
Figure 1. Predicted migration of Irganox PS 802 (0.18%) from polypropylene into olive oil at 40oC (determined to be within the SML restriction of 5 mg/kg after 10 days single use contact, 6dm2/kg).
Figure 2. Predicted mean benzophenone (UV initiator) concentrations in the wall of an outer UV cured, printed HDPE container stored for 120 days at 25oC and then filled with an aqueous food product which was then subsequently stored for 10 days at 25oC (12 successive time intervals over the 10 days storage, food product to the right of the container wall). For the modelling, the initial residual benzophenone concentration in the outer printing, prior to the initial 120 days storage, was assumed to be 1000 mg/kg.
The modelling highlights the relatively high rates of diffusion of benzophenone in polyethylene and predicted migration into the food during the 10 days contact, as shown in Figure 3 below.
Figure 3. Calculated migration of diffused benzophenone into the aqueous product over 10 days contact at 25oC.