Further insights into the mechanism of migration from the PVC gaskets of metal closures into oily foods in glass jars

Factors influencing migration from the gaskets of metal closures into oily foods were investigated. Tightening of the lid has an effect presumably through the deformation of the gasket, the amount of oil adhering to the latter, and the proportion of its surface being covered by oil. The substantial difference observed in the migration determined with the jar in an upright or a reversed position is partly related to this. The nature of the plasticizer determines the saturation in the partitioning process between the gasket and the small amount of oil in contact with the gasket as well as the adherence of oil (wettability). If saturation is rapidly reached, the frequency of exchanging the oil by shaking of the jar is an important factor. A complete exchange of the oil in contact with the gasket requires vigorous and persisting shaking, presumably because of the high viscosity and the hindered access to the angle between the gasket and the jar rim. The limited data available on long-term performance suggest that migration accelerates after roughly one year of storage. It is concluded that the extrapolation of long-term migration from short-term data presupposes a deeper investigation of the course of migration over years.