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Investigation into the effects of the freeze thaw cycle on chemical migration from packaging into foods
Project Code: A03018
Food and Environment Research Agency, Sand Hutton, York YO41 1LZ
Bradley, E ; Castle, L
The aim of this project was to test the possibility that temperature gradients experienced during the lifetime of a frozen food pack, and especially during the freeze-thaw cycle, may affect the migration of substances from the pack to the food. Two possible mechanisms have been investigated:
· a negative temperature gradient (food colder than the package) involving
release of volatile substances from the pack with condensation and trapping
on the colder food surface;
· a positive gradient (food warmer than the package) that could cause ice
formation on the cold pack surface, leading to extraction of substances that
may subsequently contaminate the food by drip during thawing.
The typical temperature gradients that a frozen foodstuff may be exposed to were established, including those that result from:
· storage in a domestic freezer;
· packaging and freezing of food in a commercial situation;
· freezing food after packaging;
· the effect of food position (i.e. in a stack) on the temperature profile;
· thawing packaged foods.
In each of these there was a temperature gradient between the packaging and the foodstuff.
These findings and conclusions on the use of food simulants as models for frozen foods, are consistant with an earlier evaluation of chemical migration during low temperature storage of packaged foodstuffs with direct contact. That study concluded that standard testing protocols using short-duration contact with simulants at 5°C are appropriate both for chilled and frozen storage of foods. This was true both for plastics tested with liquid simulants and for cartonboard tested with the solid simulant Tenax.
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