In an article published on March 3, 2016 in the peer-reviewed journal Food Additives & Contaminants: Part A, Sandra Biedermann-Brem and colleagues from the Official Food Control Authority of the Canton of Zurich, Switzerland propose a benchmark for barrier efficiency of internal bags used in food packages made of recycled paperboard. A specification and a testing method are described, which allow assessing whether the migration is reduced to a level sufficiently low so that no health risks to consumers can be assumed, for both evaluated as well as non-evaluated substances. This benchmark was adopted in the Guideline for inner bags, recently released by the Swiss Packaging Institute (SVI) (FPF reported).
The use of recycled paperboard for food packaging production is advantageous in terms of sustainability; however, there is a possibility that hazardous substances may migrate from such packaging into food. The safety assurance through chemical analysis and toxicological evaluation is not feasible because there are too many potential migrants and, moreover, their composition differs from product to product. Instead, the risks of migration can be managed by introducing internal bags with a barrier layer meant to reduce or prevent the migration from packaging. However, up to now guidelines regarding the required barrier efficiency, as well as methods for checking compliance have been lacking.
Based on the extensive literature analysis and own experimental evaluation, Biedermann-Brem and colleagues propose a specification requiring that a barrier should limit the chemical migration from recycled paperboard to below 1% of its content in the paperboard, for the period covering the product shelf life. This benchmark appears to ensure that the concentrations of non-evaluated migrants will remain below the 0.01 mg/kg food threshold, and those of evaluated substances below their respective limits.
The testing method proposed by the authors, intended to closely reflect dry foods packed in recycled paperboard with an internal bag, consists of a donor fixed on the outer surface of the internal bag film, and a receptor fixed on the opposite side. A donor is a recycled paperboard loaded with three surrogate substances of similar volatility (sufficient for the migration into dry foods) but broadly different polarity and molecular mass. The three surrogate substances chosen by the authors are n-alkane C17, 4-methyl benzophenone and dipropyl phthalate. A receptor is a silicone paper, shown to perform similarly to Tenax®. The test pack is kept at the temperature and time conditions that correspond to the shelf life of the respective product, and the surrogate substances migrating through the barrier are periodically measured by removing and analyzing a piece of receptor.
Some uncertainty in regard to consumer safety still remains, mainly in relation to the validity of the 0.01 mg/kg food threshold (since the knowledge on the toxicity of non-evaluated components in recycled paperboard is lacking), and to the adequacy of simulation of the (unknown) contaminants of potential concern by the surrogate substances. Once these uncertainties are reduced, the proposed specification can be revised.
The scientists conclude that “[t]he proposed specification and testing method should enable the optimization of internal bags in boxes of recycled paperboard with regard to all parameters relevant for food packaging, restore the use of recycled paperboard for this type of application and provide food packers as well as control authorities a benchmark for the decision whether or not a given packaging complies with the legal legislation of safety.”
Biedermann-Brem, S., et al. (2016). “Required barrier efficiency of internal bags against the migration from recycled paperboard packaging into food: a bench mark.” Food Additives & Contaminants: Part A (published online March 3, 2016).