Meaning
Substrates containing high lipid fractions that accelerate the diffusion of hydrophobic low molecular weight compounds from polymer packaging. Testing against fatty food matrices evaluates the release of plasticisers and antioxidants into edible oils or dairy products. European and American packaging regulations define specific liquid food simulants, such as vegetable oil or ethanol mixtures, to replicate this aggressive solvent action during compliance testing.
Standardised contact conditions establish maximum permitted migration limits before a material receives approval for direct food contact.
Simulant Selection
Official testing protocols mandate specific chemical media to mimic the extraction potential of butter and fatty meats without the analytical interference of natural lipids. Assigning fatty food matrices to simulant D2, which uses olive oil or sunflower oil, creates analytical challenges because the oil penetrates the polymer matrix and swells the chain structure. Alternative screening media like ninety percent ethanol or solvent mixtures accelerate testing while maintaining equivalent solubility parameters for non-polar migrants.
Migration Dynamics
Temperature and contact duration govern the rate at which organic molecules partition out of polyolefin or polystyrene containers into fat-rich foods. Higher fat concentrations increase the thermodynamic drive for non-polar additives to leach out of the container wall. When thermal processing or microwave heating occurs, diffusivity inside the polymer matrix rises sharply.
Fat Absorption
Physical swelling of polyolefin film occurs when liquid triglycerides penetrate the amorphous zones between polymer crystallites during extended storage. This structural softening increases free volume inside the polymer network, accelerating the outward transport of residual monomers and oligomers into the adjacent food layer. Moulders must select low-migration resin formulations or apply barrier coatings when manufacturing containers destined for oil-heavy food products.
