THE RELEASE OF CONTAMINANTS BY LEACHING FROM BOIL-IN BAG LAMINATES

A major problem with the development of polymeric multilayer laminates for packaging food, relates to the migration of potentially toxic substances from the packaging material into the food. These contaminants can originate from the non-food contact layer and/or from the laminate adhesive. This thesis investigates the nature, quantity and release mechanisms of contaminants from a typical boil-in bag multilayer laminate into food simulants. Global migration determinations were performed to assess conformity of both the individual polymer films and experimentally prepared laminates to 'materials in contact with food' legislation. Those indicating values in excess of the proposed European Community [EC] limit of 10 mg dm'2, were subjected to further, more detailed, analysis. Global migration of LLDPE films and laminates into fatty-food simulants gave values of ~20 mg dnr^. Flocculent precipitates were clearly visible in the oil extracts and were postulated to be the cause of the high migration result. Calcium stearate and low molecular mass oligomers (non-toxic) are suggested as the cause of the flocculate. More importantly, the contribution of potentially toxic aromatic amines to the global migration result was determined. Apparent aromatic amine levels in aqueous simulants, determined using a colourimetric assay, were found to be within the range 0.70 ± 0.07 pg dm-2 and 0.97 ± 0.09 pg dm’2 for laminates with HDPE and LLDPE primary (food contact) layers respectively. In an attempt to identify specific migrants, aqueous and oil extracts of nylon / LLDPE laminates were analysed by GC/MS. This revealed the presence of e- caprolactam (nylon monomer) and octahydrophenazine (a nylon impurity) from the nylon layer; propyl 3-(3'5' di-t-butyl-4-hydroxy phenyl) propionate (an antioxidant degradant) from the primary layer; and butylated hydroxy toluene (antioxidant) and a number of nitrogen containing aromatics from the adhesive layer. These included aniline, methylene bis-phenyl amine, dimethylaminobenzaldehyde, diphenylamine, dimethylacridine and benzylidene aniline. Other migrants identified included diphenylether, benzylbenzoate and guaiol. A number of the identified migrants are present as impurities in the films, whereas some are postulated to be the result of both degradation and secondary reactions. Thermooxidative and hydrolytic degradation mechanisms are proposed for some of the specific migrants and the remainder are explained by secondary reaction mechanisms. The levels of the above nitrogen containing aromatics were determined by HPLC with UV detection and confirmed by analysing pooled fractions by GC/MS. Apparent aromatic amine levels ranged from 0.94 ± 0.04 Lig dm-2 in aqueous extracts (aniline and MDA) to 1.87 ± 0.20 gg dm’2 for oil extracts (aniline only). These results are in good agreement with the levels indicated by the colourimetric assay. However, the presence of ±ese analytes could not be confirmed by GC/MS. Generally, contaminant levels were 2 - 4 times higher in oil simulant extracts. The toxicity of all the identified contaminants has been reviewed, and the effect of the levels found on the health of various species, including humans discussed.