Migration from non-ovenable food contact materials at elevated temperatures
A major problem associated with the development of complex polymeric materials for food contact applications is the potential for migration of toxic substances from the polymer to the food. This thesis investigates the transfer of migrants from non-ovenable food contact materials at elevated temperatures, and several applications where migration has occurred have been identified. Boil in the bag applications lead to exposure times of 30 - 120 minutes for complex multilayer laminates, whilst plastic kettles are repeat exposure items, and plastic 'vacuum flasks' have a potential for up to 4 hours exposure. Analytical techniques including, GC-MS, LC-MS, HPLC and UV spectroscopy have been employed to quantify the species migrating from these food contact materials into aqueous and oil simulants, and to ensure that they conform to the implemented EC restrictions. Olive oil is a stipulated EC fatty food simulant, but it is unsuitable for specific migration analyses since it contains many interfering compounds. These could not be eliminated by repeated solvent extraction, and a silicone oil was therefore substituted. In an attempt to identify the species migrating into aqueous and fatty food simulants both the final materials and also the individual components i.e. nylon, adhesive, polyethylene and polypropylene were examined separately. HPLC techniques have been developed to quantify both the known levels of antioxidants present in the polymers and also the anticipated degradation products from these materials. Typical levels of antioxidants in simulants range from <0.1 (aqueous) to 45j..lgdm-2 (oil) and <0.1 (aqueous) to 200j..lgdm" (oil) for antioxidant degradation products. In commercial boil in the bag laminates the major migrants have been shown to be derived principally from the nylon film, and the polyurethane adhesive used to fabricate the laminate. Le-MS investigations have confirmed the presence of the residual monomer Ecaprolactarn and its cyclic oligomers (up to the nonarner) in aqueous food simulants boiled in direct contact with the nylon 6. This technique has also identified the main migrants from the aliphatic and aromatic polyurethane adhesives to be residual oligomers from the polyols. Any residual isocyanates in the adhesive are converted to the corresponding amine, and colourimetric assays have determined levels between 1.1 and O.lj..lgdm". Measured, migration levels into fatty food simulants were found to be greater than in aqueous food simulants. However, none of the material examined showed an overall migration value greater than the EC limit of 10mg dm" for single sided testing. Some instances were found where the consumer was instructed to boil the dry food part of a boil in the bag meal in the same water as that used to heat the pouch containing the meat, and under these circumstances a total migration value for the laminate greater than 10mg dm-2 was measured.