Effectiveness of polypropylene film as a barrier to migration from recycled paperboard packaging to fatty and high-moisture food.

The capability of a polypropylene (PP) film barrier to prevent migration of residual contaminants from recycled paperboard into food simulants was studied. Anthracene, benzophenone, methyl stearate and pentachlorophenol were chosen as chemical surrogates to represent classes of contaminants likely to be found in recycled paper/paperboard. Each surrogate was spiked into a test specimen made of seven thin virgin paper layers at concentrations of 1-50 mg kg(-1). Test specimen were dried, stacked and sandwiched with PP films, laminated with PP film and then subjected to migration experiments using a compression cell maintained at 100 degrees C for 2 h. The concentration of the surrogates in the test specimen and in 95% ethanol, isopropanol and 10% ethanol food-simulating solvents was determined by gas chromatography with flame ionization and electron capture detection. The results show that although the concentrations of the surrogates in the food simulants decreased with an increase in PP film thickness, they were still high and generally resulted in dietary concentrations >0.5 microg kg(-1), the level that US Food and Drug Administration would equate with negligible risk for a contaminant migrating from food packaging. Only at the lowest spiking level (1 mg kg(-1) benzophenone) did migration from the paperboard through a 0.127-mm PP film result in a dietary concentration of

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.

Volatile and non-volatile compounds in irradiated semi-rigid crystalline poly(ethylene terephthalate) polymers.

In this study two different semi-rigid crystalline and oriented polyethylene terephthalate materials were used and were irradiated at 25-kGy dose at room temperature by using a caesium137 radiator. Volatile and non-volatile compounds present in the irradiated materials were identified and quantified. The qualitative results obtained from HS/GC/TCD/FID analysis at room temperature showed volatiles could not be identified. The HS/GC/MSD analysis performed at 106 degrees C showed that the irradiation generated 668-742 micrograms/kg formic acid, 868-922 micrograms/kg acetic acid, 17-32 micrograms/kg 1,3-dioxolane, and 47-71 micrograms/kg 2-methyl-1, 3-dioxolane based on PET weight. The results obtained from the thermal desorption and GC/MSD performed at 200 degrees C showed that 10-12 mg/kg acetaldehyde, 479-975 micrograms/kg 1,3-dioxolane, and 6.6-11.2 mg/kg methyl-1, 3-dioxolane were detected after irradiation. The concentrations of the two dioxolanes found from thermal desorption were much higher than those observed in the HS, although formic and acetic acids were not detected. It is possible that the formic and acetic acids produced by irradiation underwent further reactions with ethylene glycol during thermal desorption to form the dioxolanes. The soluble solid extracted from various PET specimens before and after irradiation were in a range of 0.67-0.78%. PET cyclic trimer is the major component and is present at 0.41-0.50%, accounting for more than 50% of the percent total solid in PET. Statistically, irradiation did not increase the soluble solid and cyclic trimer. The overall results suggest that 25-kGy irradiation had a significant effect on increasing the volatile but not the non-volatile compounds detected in the PET specimens.

Analytical procedure for quantifying five compounds suspected as possible contaminants in recycled paper/paperboard for food packaging.

Because contaminants in recycled paper intended for food packaging could be a risk to public health, analytical methods are needed to identify and quantify residues of concern in paper/paperboard. The U. S. Food and Drug Administration is considering development of a guidance document for testing levels of contaminants that might be retained through paper recycling processes. An analytical procedure was developed using paper spiked with suspected contaminants at concentrations of 1-50 ppm in the paper. Benzophenone, dimethyl phthalate, anthracene, methyl stearate, and pentachlorophenol were introduced by soaking the paper in a solution in acetone at 25 degrees C for 24 h; the paper was removed and dried by evaporating the solvent with nitrogen. The model contaminant residues were extracted from the paper using ultrasonication and quantified by GC with flame ionization and electron capture detectors. Recoveries from the spiked paper were 80-109% with a repeatability of +/-4%. The method was also used to analyze commercial recycled paperboard to validate its applicability.

Migration of residual contaminants from secondary recycled poly(ethylene terephthalate) into food-simulating solvents, aqueous ethanol and heptane.

This study measured the migration of benzene, butyric acid, dodecane, octadecane, tetracosane, diazinon, lindane, and copper (II) ethyl hexonate from poly(ethylene terephthalate)(PETE) sheets into the food simulants, 8% ethanol/water and n-heptane. The contaminated PETE sheets were extruded from PETE chips that had been previously contaminated but were washed, dried, and remelted. The level of these contaminants remaining in the extruded sheets ranged from benzene at 0.6 mg/kg to copper salt at 24 mg/kg. The extraction data demonstrate that migration of the residual contaminants from the extruded PETE sheets resulted in concentrations lower than 10 micrograms/kg in the food simulants. At very high residual concentrations of butryic acid (147 mg/kg) and benzene (218 mg/kg) in sheets made from unwashed PETE, higher amounts of the contaminant migrated into the food simulants. This migration resulted in contaminant concentrations exceeding 10 micrograms/kg and suggests that unwashed recycled PETE may not comply with FDA requirements. The crystallinity of extruded PETE sheets in this study ranged from 5 to 15%, which is lower than that of most commercial PETE (30%). Therefore, the migration data obtained from these test samples represent the most severe conditions for conservative exposure evaluations.

Determination of benzene residues in recycled polyethylene terephthalate (PETE) by dynamic headspace-gas chromatography.

A dynamic headspace-gas chromatography (HS/GC) method was developed to quantitate benzene in recycled PETE material derived from 21 PETE beverage bottles. The analytical system consisted of a purge-and-trap apparatus which was interfaced directly with a gas chromatograph/flame ionization detector. Cryofocusing and non-cryofocusing GC systems were used. The technique was applied to spiked PETE test samples which were prepared at various benzene concentrations ranging from 100 ppb to 117 ppm. The initial spiked benzene concentration in the PETE test samples was determined gravimetrically. The HS/GC technique was limited by the slow desorption rate of benzene from the PETE matrix; as a result, multipurges were performed at 60 degrees C. Regression analysis was done on the multipurge data to develop a desorption model which would predict the total amount of benzene in the PETE. The calculated results agreed with the experimental recoveries within +/- 10%. Recovery depended on the initial benzene level in the PETE and ranged from 70 to 90% after the first five purges.

A dispersion model for predicting the extent of starch liquefaction by Bacillus licheniformis alpha-amylase during reactive extrusion.

A Baker-Perkins corotating twin screw extruder was used as a bioreactor to hydrolyze pregelantinized corn starch by themophilic Bacillus licheniformis alpha-amylase. The extruder was modeled as a tube, and characterized as a closed system. This characterization is not in the thermodynamic sense; rather, it relates to the profile of a tracer fluid upon entry to and exit from the reaction zone. The reaction kinetics were modeled by a modified first-order equation, which allowed the dispersion equation to be solved analytically with the Danckwerts boundary condition. Data from several extrusion runs were super-imposed to obtain a profile to evaluate the model. The dispersion number, determined from the first and second moments of the RTD curve, was primarily a function of the length of the reaction zone. There was good agreement between predictions and experimental data, especially at low dispersion numbers. In general, the axial dispersion model appears to be suitable for analysis of enzymatic reactions of up to 30% conversion. At a fixed flow rate and constant temperature, the extent of starch conversion depends significantly on moisture content, residence time and enzyme dosage, but not on screw speed.