Migration from recycled paperboard was monitored after 2, 4 and 9 months of storage for six test foods industrially packed in five configurations, four with internal plastic films. After 9 months, the migration of mineral oil saturated hydrocarbons into foods directly packed in the paperboard amounted to 30-52 mg/kg, which corresponded to 65%-80% of those of a volatility up to that of the n-alkane C₂₄ in the paperboard. The concentration of the migrated aromatic hydrocarbons in the foods ranged from 5.5 to 9.4 mg/kg. More than half of this migration occurred in the first 2 months. Differences between the foods amounted to mostly less than a factor of 2 and seemed to be related to porosity or permeability more than fat content. Nine photoinitiators were detected in the paperboard, of which eight migrated into the packed food at up to 24%. Several plasticisers were present in the recycled paperboard, but only butyl phthalates showed significant migration. After 9 months, up to 40% of diisobutyl phthalate and 20% of dibutyl phthalate migrated into the food with direct contact. The internal polyethylene film hardly slowed migration, but the film and the tray absorbed approximately three times more mineral oil than the food, despite constituting merely 4% of the mass of the pack. Oriented polypropylene strongly slowed migration: The highest migration of saturated hydrocarbons measured after 9 months (2.3 mg/kg) corresponded to only 3% of the content in the paperboard and included migrated polyolefin oligomeric saturated hydrocarbons. Coating of polypropylene with an acrylate further slowed the migration, but the migration from the paperboard was still detectable in four of the six samples. Polyethylene terephthalate was a tight barrier.

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As an option to reduce migration from boxes of recycled paperboard into the packed food, it was proposed to apply a functional barrier layer to the internal surface of the paperboard. However, with most designs of the closures, flaps expose unprotected outer surface to the inside of the box, that is, migration may occur around the barrier, and the closures are not airtight. A pilot study provided first data on the contribution of the closures to the migration into the packed food during long‐term storage of a dry food like rice. Three closure designs were tested with the surrogates also used for determining barrier efficiency and applying the criterion that no more than 1% of the substances in the board should reach the food. Boxes were formed from paperboard with an efficient PET/PE barrier and spiked with surrogate substances. They were filled with rice and stored under various time/temperature conditions. Two closure designs represented those commonly observed for dry foods; the third avoided flaps reaching into the box by joining barrier surface against barrier surface. For the first two closure designs, migration into rice reached several per cent after just a few weeks. The third design resulted in clearly lower migration but still more than 1%. It is concluded that functional barriers on the internal surface of recycled paperboard may only reduce the migration below the proposed 1% criterion if specially designed closures are used.

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