Effects of gamma- and electron-beam irradiation on semi-rigid amorphous polyethylene terephthalate copolymers.
Two semi-rigid amorphous polyethylene terephthalate copolymer materials (in both sheet and powder forms) containing 3% 1,4-cyclohexane dimethanol (CHDM) and 31% CHDM were irradiated at 5, 25 and 50 kGy at ambient temperature with a (60)Co radiator or an electron-beam accelerator. After irradiation, volatiles were determined using static headspace sampling with capillary gas chromatography and mass selective detection or flame ionization detection (HS/GC/MSD or FID). Non-volatiles were extracted with 10% aqueous ethanol and 100% n-heptane food-simulating solvents, maintained at 40 degrees C for up to 10 days. The non-volatiles in the materials and those migrating into the food-simulating solvents were determined by high-performance liquid chromatography (HPLC) with ultraviolet and/or photodiode array detection. The results obtained from the HS/GC/MSD suggest that no new chemicals were detected by either gamma- or e-beam irradiation when compared with non-irradiated specimens. The major volatiles in the copolymers were acetaldehyde and 2-methyl-1,3-dioxolane. The concentrations of acetaldehyde increased from 1.24-1.96 mg kg(-1) to 1.94-3.65, 3.52-7.23 and 5.45-15.37 mg kg(-1) after exposure to 5, 25 and 50 kGy doses, respectively. The concentrations of 2-methyl-1,3-dioxolane decreased from 2.49-5.26 mg kg(-1) to 2.07-3.13, 1.33-2.14 and 0.64-2.24 mg kg(-1) after exposure to 5, 25 and 50 kGy doses, respectively. The results of analysis of the copolymers for non-volatiles show that irradiation did not produce any new detectable non-volatile chemicals. A 5 kGy dose had no detectable effect on either copolymer. The 25 and 50 kGy doses had slightly different effects with respect to gamma- and e-beam irradiation on low MW oligomers. However, these increased doses did not significantly affect migration. The concentration of most low molecular weight oligomers migrating into 10% ethanol and 100% heptane was < or =2 ng g(-1) of each oligomer for both copolymers. The cyclic trimer migrating from the 3% CHDM copolymer was approximately 4 ng g(-1); it was 3 ng g(-1) for the 31% CHDM copolymer. The overall results suggest that irradiation significantly increased levels of acetaldehyde but had no effect on non-volatile compounds migrating into food simulants.
Komolprasert
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Division of Food Processing and Packaging, US Food and Drug Administration and National Center for Food Safety and Technology, Illinois Institute of Technology, Summit-Agro, 60501, USA. Vanee.Komolprasert@cfsan.fda.gov
McNeal
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TP
Begley
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D004583:Electrons; D005506:Food Contamination / Q000032:analysis*; D005514:Food Irradiation; D018857:Food Packaging; D005720:Gamma Rays; D006801:Humans; D011093:Polyethylene Terephthalates / Q000737:chemistry / Q000528:radiation effects*
D011093:Polyethylene Terephthalates