On July 1, 2013, the peer-reviewed journal Food Chemistry published the scientific paper “Recycled paper-paperboard for food contact materials: contaminants suspected and migration into foods and food simulant” (Suciu et al. 2013). The researchers from Università Cattolica del Sacro Cuore, Piacenza, Italy, present a new method for analyzing both the presence of contaminants in food packaging and their migration into food stuff. 17 samples of paper and paper-board composed of varying contents of recycled fibers were analyzed for the presence of bisphenol A (BPA), bis (2-ethylhexyl) phthalate (DEHP), nonylphenol monoethoxylate (NMP) and nonylphenol di-ethoxilate (NDP). In accordance with the proposed food simulant for dry food (Regulation (EU) 10/2011) the researchers used Tenax®, in addition to the dry foods sugar and salt, for migration testing. Tenax®, or poly(2,6-diphenyl-p-phenylene oxide, is a porous polymer resin employed for trapping (semi-)volatile chemicals.Untreated samples and samples fortified (“spiked”) by surrogates for BPA and DEHP were exposed to sugar and salt matrices at normal room humidity and increased room humidity for 30, 60 and 100 days. In the Tenax® matrix, one spiked and one unspiked sample were exposed at 40°C for 10 day. In order to avoid contamination by e.g. inks, the printed outer layer of all samples was removed prior to the extraction process and migration experiments. The extraction of BPA was carried out in ethanol and for DEHP, NMP and NDP in acetone–hexane 4:1 with Soxhlet from small samples (0.5 x 1.0 cm), followed by analysis via gas chromatography coupled with mass spectrometry (GC-MS). Limits of quantification (LOQ) and the limit of detection (LOD) were determined for the recovery experiments for one paperboard sample, salt, sugar and Tenax®. By standardizing the measurements internally, the concentrations of contaminants are inherently corrected for recovery losses.
Contaminants presence. The only contaminant present in all samples was BPA, found at levels from 0.41mg/kg up to 26.4 mg/kg . Significantly more BPA was found in samples from recycled fibers compared to packaging made out of virgin fibers. DEHP was found at concentrations from 0.97±0.43 mg kg^-1 up to 66.3 mg kg^-1 in 12 out of 17 samples. Like BPA, DEHP was found more abundantly in samples made from recycled fibers compared to the virgin samples. Both nonylphenols, NMP and NDP, were measured at concentrations much lower than BPA and DEHP. NMP was present in 8 samples and was found at concentrations ranging between 0.10 and 0.69mg/kg, whereas NDP, present in 16 samples, was measured at levels from 0.11 to 0.62 mg/kg. Concentrations of NMP and NDP did not significantly differ among virgin and recycled fibers. Suciu and colleagues speculate that BPA and DEHP are present in recycled fibers, whereas NMP and NDP are substances added in the recycling processes.
Contaminants migration. Migration experiments showed that the diffusion of BPA from the unspiked sample into salt was significantly higher (p=0.01) after 30 days than after 60 days. The same observations were made for migration into sugar with increased humidity. For the remaining matrices no significant differences were found. Suciu and colleagues concluded that 30 days are sufficient to reach equilibrium at room temperature and humidity. In accordance with the literature the scientists found that longer periods, higher humidity and higher concentrations of BPA in the samples did not affect when equilibrium was reached.
For DEHP slightly higher migration was measured than for BPA. DEHP migrated into Tenax® at significantly higher levels from the spiked sample than from the unspiked sample. Suciu and colleagues explained this by stronger retention of substances from recycled paperboard samples than from the same spiked sample. No differences were found for migration into salt and sugar. This led the researches in line with the literature to rate Tenax® suitable for the experimental assessment of DEHP migration into dry food and supposedly more suitable than sugar.
For the migration of the two nonylphenols no significant differences were found among the three matrices tested. For NDP significantly higher migration was measured after 30 days at increased humidity into sugar compared to migration after 60 days at increased humidity into sugar and at room humidity into sugar and Tenax®. Suciu and colleagues pointed out that these results might indicate that Tenax® might not be suited for testing migration of these molecules. In addition, they stressed that more research is needed to clarify these findings.
By testing virgin and recycled paper and paper-board packaging materials Suciu and colleagues demonstrated the applicability of the presented procedure elucidating the presence and migration of contaminants into dry food. Concluding, the scientists point out that the selected contaminants were present at rather high levels in the tested samples. The levels of measured contaminants were strongly dependent on the source of the food contact material, such as percentage of recycled fibers. BPA and DEHP for example were found at minimum levels in packaging materials either where references were lacking for the presence of recycled fiber or where regulation requests the application of virgin fibers. For certain products, e.g. takeaway pizza boxes, Italian regulation prescribes the use of virgin fibers. On the other hand, the nonylphenols, NMP and NDP, were found at highest concentration in recycled paperboard. The scientists explain that BPA is a contaminant of primary matter (recycled fibers) in contrast to nonylphenols which are added in the recycling process. The review’s authors attest that the food simulant Tenax® serves well for quantifying contaminant migration from paperboard into dry food. In summary, recycled paper and cardboard were shown to be sources of some endocrine disrupting chemicals and may not be safe for food contact applications.
References
Suciu, N.A. et al. (2013) “Recycled paper-paperboard for food contact materials: contaminants suspected and migration into foods and food simulant.” Food Chemistry (published online 2 July 2013)
