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Model compounds (chosen to provide a range of volatilities and polarities) were incorporated into cartonboard and polyethylene film and the migration of these compounds was investigated into foods and food simulants. The migration into foods (beefburgers, green beans and chips) from impregnated packaging materials (cartonboard and polyethylene) was studied following freezing after packing, and 20, 60 and 240 minute thaw periods (i.e. Mechanism One).
In separate studies, a polar compound was incorporated into the packaging to assess migration and transfer via any condensate formed on the internal packaging surface (i.e. Mechanism Two).
Assessment of packaging materials for chemical migration, conventionally employs standard test conditions of time and temperature linked to the expected conditions of use. However, it is possible that dry or solid frozen foods do not behave in the same way as other foodstuffs when they are exposed to the food packaging. With such foods, intimate contact between the food and the package is small and migration may be dominated by the diffusion of volatile substances across the air gap as opposed to by direct contact.
The aim of this project was to test the possibility that the temperature gradients that may be experienced during the lifetime of a frozen food pack, and especially during the freeze-thaw cycle, affect the migration of substances from the pack to the food. Two possible scenarios exist by which migration could occur from the packaging material to the food:
Mechanism One: release of volatiles by the packaging and cold trapping by the foods.
Mechanism Two: ice crystal formation on the packaging surface with subsequent drip onto the food during thawing.
<p>Find more about this project and other FSA food safety-related projects at the <a href="http://www.food.gov.uk/science/research/" target="_blank">Food Standards Agency Research webpage</a>.