Migration testing on food contact materials requires analytical know-how, specialist tools as well as a deep understanding of current food contact legislation. At Siegwerk, we have accumulated vast knowledge within this field. Besides various test laboratories we have established a global analytical network with core competencies not only in Europe but also within the Asian market. As a special service to our customers, we also recommend independent external analytical institutes for the migration testing of food packaging printed with Siegwerk inks and varnishes.
We have also developed our own migration cell “Sieg-Mi-Flex” together with a partner. This unique cell is used for sample preparation in the measurement of migration of low molecular weight substances from packaging materials and subsequent analytical quantification. Learn more about migration and migration testing by exploring our FAQ section.
Frequently Asked Questions
What is migration?
Migrants are substances which, due to their chemical characteristics and molecular size, move from a printed layer into the packed food. In line with the European Food Safety Authority (EFSA), it is commonly accepted that substances with a molecular weight higher than 1000 Daltons do not migrate. There are, however, different types of migration:
a) Set-off migration
Migrants can migrate from one layer to another, such as a surface printed layer to the non-printed food contact surface which is later brought into contact with food. If these are in direct or close contact like in a reel or a stack after printing, set-off migration can occur due to the pressure existing in the reel or stack.
b) Diffusion migration
Small and mobile molecules can easily penetrate into and diffuse across packaging material layers. This can occur even if the printed material has not yet been converted into a food package and filled with food, or later on when the printed package is filled with food and the food starts to “extract” the migrants from the packaging material.
c) Gas-phase migration
Migrants can also migrate from a cardboard (the “releasing reservoir”) via the gas phase within the pack, to end up in food which acts as “recipient reservoir”. This can, for example, occur with migrants such as mineral oils or some UV photoinitiators that might not be generally known as being volatile, e.g. organic solvents.
Which factors influence migration?
The following factors most significantly contribute to migration:
- Size of migratable substances: small substances have a higher migration tendency
- Storage temperature: the higher the temperature, the faster the migration of substances
- Storage time: the longer the exposure time in food packaging, the higher the risk of migration
- Packaging structure: different substrates have different functional barrier properties (PE < PP homo < PET, PBT, PS < Alu)
- Kind of foodstuff packed: different polarities of foodstuff and packaging material influence the migration behavior
- Application weight: the lower the amount of ink applied, the lower the migration risk
- Food packaging size: the bigger the amount of food packed to the packaging’s surface area, the smaller the risk of potential migration
How can migration be prevented?
Generally, migration can only be prevented by an absolute barrier. However, there are many factors influencing the efficiency of barriers, amongst others the material itself, the thickness of the layer or the filling conditions of the packed food. Aluminum foil (min. 6 µm) and glass can be considered as an absolute barrier. On the other hand, even rigid materials such as PE bottles are not always a sufficient barrier.
How is migration testing anchored within current legislation?
According to the Commission Regulation (EU) No 10/2011, “demonstration of compliance may be based on migration testing. As migration testing is complex, costly and time consuming it should be admissible that compliance can be demonstrated also by calculations, including modelling, other analysis, and scientific evidence or reasoning if these render results which are at least as severe as the migration testing. Test results should be regarded as valid as long as formulations and processing conditions remain constant as part of a quality assurance system.”