In an article published on February 22, 2016 in the peer-reviewed journal Food Additives & Contaminants: Part A, Isabel Clemente and colleagues from the Department of Analytical Chemistry, University of Zaragoza, Spain, report on the identification of volatile compounds migrating from printing inks in multilayer food packaging materials. The scientists also investigate whether such migration can be avoided by using an overprint varnish or varying the ink position in the multilayer structure.
Different substances can migrate from inks and varnishes present in multilayer materials used for food packaging, particularly due to set-off phenomena (FPF reported). The researchers assessed the migration from two groups of materials manufactured by Goglio S.p.A. (Daverio, Italy), one based on paper and containing nitroacrylic inks, and another one based on polyethylene terephthalate (PET) with nitropolyurethane inks. In all materials, polyethylene was used as the internal layer, and the different layers were joined by polyurethane adhesives. Four food simulants (50% and 95% ethanol, isooctane, and Tenax®) were used. Migration tests were carried out at 40°C and 10 days, except for isooctane where migration was assessed at 20°C and 2 days.
A total of 149 and 156 volatile compounds were found in migrates from paper-based and PET-based sets, respectively. In both sets, more migrants were detected in isooctane and 95% ethanol, indicating that higher migration would occur in fatty foods as compared to aqueous ones.
For paper-based materials, the solvent 1,2,3-propanetriol triacetate (CAS 102-76-1) and the plasticizer tributyl acetyl citrate (CAS 25360-09-2) were present in all simulants. Both are listed in the Swiss legislation and in the European Printing Ink Association (EuPIA) inventory list. Application of an overprint varnish to the external side of the multilayer material led to a decrease for some of the migrants, most of them coming from inks but also from other components, such as polyurethane adhesives. Some of the detected substances were assigned to Cramer class III (see FPF article on the Threshold of Toxicological Concern), underscoring the benefits of applying the protective overprint varnish, which apparently could mitigate or prevent the set-off process. However, both 1,2,3-propanetriol triacetate and tributyl acetyl citrate did not decrease, or even increased in some simulants, after varnish application, likely due to their presence in the varnish itself.
For PET-based materials, migration was observed to be different depending on the presence or absence of an ink layer as well as its position within the structure. Tributyl acetyl citrate and a pigment additive, 1,2,3-propanetriol diacetate (CAS 25395-31-7), were found in the migrate to all food simulants. When the ink was placed under a PET layer, most of the ink-related migrants, including several belonging to Cramer class III, disappeared; however, other migrants increased their concentrations or even appeared anew.
Clemente, I. et al. (2016). “Migration from printing inks in multilayer food packaging materials by GC-MS analysis and pattern recognition with chemometrics.” Food Additives & Contaminants: Part A (published online February 22, 2016).