Chemicals used in adhesives for food labels can seep through packaging and contaminate food, according to research published by the Royal Society of Chemistry.
Strict EU regulations exist for the use of plastics in food packaging, but there is no specific legislation about the chemicals in adhesives used to attach sticky labels directly or indirectly to food packaging, or to fix packaging layers together.
Now, a team of scientists studying compounds in acrylic adhesives has discovered that some chemicals can diffuse through the packaging and reach the food inside. One of those is considered highly toxic and found in high concentration in some adhesives.
The team, from the University of Zaragoza, Spain, studied four different acrylic adhesives and examined in detail the 11 compounds found in them. Some were solvents, while others were residual monomers or impurities remaining from manufacture.
Of the 11 compounds, four migrated all the way into the food stimulant used for the experiments – with two being higher in toxicity than recommended by the International Life Sciences Institute Europe, the body that investigates food safety and toxicology.
One of these, 2,4,7,9-tetramethyldec-5-yne-4,7-diol, which is used as a non-ionic surfactant, has a high concentrations in some adhesives and this, together with its high toxicity, makes it a particular target for future studies, said Cristina Nerín, who led the team.
To conduct the study, Nerín placed a layer containing an adhesive onto a layer of packaging material (polymer or paper) that covered Tenax, a food simulant. Analysis of the layers using mass spectrometry determined whether, and how far, any chemicals had diffused through.
Valérie Guillard, an expert in food technology and packaging at the University of Montpellier, France, said that she believes Nerin’s studies show that ’migration of adhesive compounds is possible and at a level that could raise safety concerns’.
The researchers’ results are published in the latest edition of the RSC’s Journal of Materials Chemistry.