Novel test approach for evaluating barrier properties of food contact materials against mineral oil contaminants

Recently, mineral oil (MO) residues in food have raised concern because there is a potential risk that consumers are exposed to a range of MO hydrocarbons (MOH) via food (1). The European Food Safety Authority (EFSA) published an opinion on mineral oil in 2012 (1). Concern was in particular expressed for the MO aromatic hydrocarbons (MOAH), because EFSA assumed the presence of genotoxic carcinogens. Potential background exposure to saturated MO hydrocarbons (MOSH) via food was also considered a concern. MOH contamination of food may be caused by printing ink residues found in packages from recycled paperboard but originates also from certain additives, processing aids, and lubricants. As a result of the concerns, an ordinance for food and food packaging is under preparation in Germany. The ordinance will set limits for MOSH and MOAH in food and food contact materials manufactured using recycled paper pulp, to protect consumers from potential health risks (2). The crucial question is whether MOH compounds can penetrate through barriers at the food contact side of the recycled packages or indirectly through inner packages of virgin paperboard into into the food. Several methods to test the food contact materials for MOH transmission have been introduced (3,4) including the use of test packs with layers of donor paper, a spacer paper, the tested barrier layer and a receptor. An alternative method is the permeation cell method. A third alternative uses test cups for hexane vapour transmission rates measurements. The objectives of this work is to develop a reproducible barrier test method where the mineral oils are introduced to the test system in the gas phase. The focus is on using surrogate compounds of a relevant molecular weight range for the drafted German ordinance. Finally, the equipment and materials used should be commercially available. In the new approach, the selected surrogate compounds representing MOH were introduced in the gas phase by saturating a closed space with them. Inside the closed space a fixed amount of food simulant, typically modified polyphenylene oxide TenaxTM, was placed into commercial test cups. The materials tested for their barrier properties were fitted into the lid of the test cups. After the test period, the cups were removed from the closed space and the food simulant was extracted. Finally, the content of the surrogate compounds in the extract was determined by gas chromatography and the transmission rates were calculated. Boards with different barrier coatings were tested with this new method and theoretical diffusion constants were determined using a physical model for the experimental setup.