Taped Barrier Test for Internal Bags Used in Boxes of Recycled Paperboard: The Role of the Paperboard and Its Consequence for the Test

Abstract

Internal bags with a functional barrier are a promising solution to render recycled paperboard acceptable for food packaging. Producers and users of such bags as well as control authorities need a tool to evaluate whether a bag satisfies the requirements of safety. In the previously proposed methods, the criterion focused on the permeability of the barrier layer. This neglected the influence of absorption or adsorption of the substances in the paperboard and the plastic of the bag. To take these contributions into account, it was proposed to change the criterion and use the percentage of the amount of (surrogate) substances in the recycled paperboard that passes into the food. This paper explains this, in particular how the method better reflects the reality in a pack of food. Firstly, donors should be prepared from recycled paperboard, as the behaviour differs from that of paper. Secondly, absorption into the paperboard seems to be a slow process. It was noted that freshly added surrogate substances were easily extracted by methyl tert-butyl ether, but the extraction yield decreased during storage over some weeks. To catch this reality of the substances in the paperboard, donors need to be conditioned before use. Finally, absorption in the paperboard may depend on the concentration, which prompted a further reduction of the amounts of the surrogate substances used for testing. It turned out that usually the hydrocarbon (C17) determines the barrier efficiency; triethyl citrate is no longer used, as it was never a relevant surrogate.

Taped Barrier Test for Internal Bags Used in Boxes of Recycled Paperboard: Update of the Method

“…However, extractability decreased with time and temperature: after some months, only a small fraction of the polar components could be extracted with MTBE, even over days, with increased temperature and the help of ultra sound. Then, admixture of methanol, warming and more time was required to achieve complete extraction …”

“…Finally, the number of surrogate substances was reduced to three: in the many tests performed, TEC had never been the determinant substance, because of its strong absorption into the paperboard. As it was the most demanding substance for GC analysis with regard to the inertness of the analytical system, particularly at the reduced levels in the donor, its elimination rendered the analysis more robust.…”

“…For reasons described in ref ,. the method needed further amendments, primarily because factors other than slowed diffusion through the barrier layer needed to be better taken into account.…”

“…Moreover, it was observed that integration of polar substances into the paperboard takes time: apparently polar substances slowly diffuse into quasi‐solid parts, which strongly decreases the migration from the paperboard the longer the latter is stored. As a result, the migration of polar substances may be sufficiently low with a weaker or even without a barrier . Absorption into the paperboard also depends on concentration (saturation), apparently particularly for C17, which is commonly the surrogate substance determining the barrier efficiency.…”

“…Absorption into the paperboard also depends on concentration (saturation), apparently particularly for C17, which is commonly the surrogate substance determining the barrier efficiency. Because various recycled paperboards behaved similarly and their humidity in the range of 0–5% was shown to play a minor role, these factors did not seem to require special attention.…”