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Nylon 6 and nylon 12 food packaging materials used as sausage casings are typically exposed to fatty food on one side and boiling water on the other during the cooking process. To simulate the migration behaviour under these conditions, a special migration cell was constructed and filled with olive oil on one side of the polymer and water on the other to find out what amounts of the migrants will transfer to either side and phase at 100 degreesC. Results show that when a nylon 6 film is exposed to the conditions as described above, total mass transfer of the monomer-caprolactam-into the water phase occurs after 2 h at 100 degreesC. Nylon 12 sausage casings release similar amounts of their monomer-laurolactam-into both the aqueous and oil phase. An existing computer migration model was adapted to simulate the situation of simultaneous two-sided migration applying previously determined diffusion and partitioning coefficients. The suitability of the model was confirmed by experimental data.

The effects on ionising irradiation on polymer additives, monomers and polymers themselves have been investigated. Changes of initial concentrations of certain additives and monomers, a change in their specific migration as well as sensory changes of the polymers were examined. Polymer stabilizers such as Irganox 1076 and Irgafos 168 used in polyethylene were found to be degraded by ionising radiation. Decreased concentrations of stabilisers in polyolefins led to lower specific migration, however, not to lower overall migration into food simulants. Irganox 1076 levels in polystyrene did not change up to irradiation doses of 54 kGy. Sensory properties of LDPE, HDPE, PA6 and PA12 worsened, while sensory properties of PS improved with increasing irradiation doses.

The paper describes a project with the main objective of developing the know how to produce certified reference materials (CRMs) for specific migration testing. Certification parameters discussed are the initial concentration of the migrant in the polymer (C-P,C- 0) and the specific migration into a food simulant under certain temperature/time conditions. Sixteen preliminary candidate CRMs were defined and produced. The most important polymers (low- and high-density polyethylene ( LDPE and HDPE), polypropylene ( PP), polystyrene (PS), polyethylene terephtalate (PET), plasticized polyvinyl chloride (PVC), rigid PVC, polyamides (PA)) and additives as well as monomers representing different physicochemical properties as target substances for migration were chosen. The stability and homogeneity of the migrants in the materials were tested and methods for the determination of the certification parameters were developed and validated. > From the 16 materials produced, the six most suitable CRM candidates (LDPE//Irganox 1076/Irgafos 168, LDPE//1,4-diphenyl-1,3-butadiene DPBD), HDPE//Chimassorb 81/Uvitex OB, PP homo//Irganox 1076/Irgafos 168, HIPS, 1% mineral oil//styrene, PA 6//caprolactam) were selected. The feasibility of CRM production for the six candidate materials was demonstrated and a trial certification exercise was performed with participation of all four partner laboratories. All six materials showed suitable properties for future production as certified reference materials.

The migration of laurolactam and cyclic di- and trimer of nylon 12 was assessed using three different films and five food simulants (olive oil, isooctane, 95% ethanol, 50% ethanol, water). Substitute test conditions for migration into olive oil according to European Union Directive EC/97/48 were applied using 95% ethanol and isooctane. Results showed that 95% ethanol overestimated while isooctane underestimated the respective migration into olive oil. Water was the best olive oil substitute, as migration of laurolactam into water and olive oil using the same temperature gave similar results. Additionally, diffusion kinetics of laurolactam were investigated by migration kinetic studies using isooctane and olive oil. Diffusion coefficients determined with isooctane were significantly higher than those found using olive oil. It was proved that isooctane had an interaction and olive oil was inert to the polymer. The diffusion conductance parameter, A(p), for nylon 12 determined using olive oil ranged from 0.3 to 0.6.

Analytical methods for the determination of laurolactam--the monomer of nylon 12--as well as the cyclic dimer and trimer were established. High performance liquid chromatography using ultraviolet (HPLC-UV) and mass spectrometric detection (HPLC-MS) were both found suitable to identify and quantify monomer, cyclic dimer and trimer well below the specific migration limit (SML) of laurolactam, being 5 mg/kg of food (simulant). Gas chromatography with flame ionisation detection (GC-FID) showed to be an appropriate method for the detection of only laurolactam in aqueous and fatty food simulants. Food simulants could be analysed directly by all three methods, or after a change of solvents. For olive oil, a method for sample clean-up by size-exclusion chromatography (SEC) was established.