How to avoid ink migration into food in packaging printing

Ink is a basic element both to exploit the communicative potential of packaging and to ensure its protective function

One of the main issues to keep in mind in food packaging printing is consumer safety. Therefore, there are strict regulations regarding ink components and application conditions on different substrates. The ultimate goal is to ensure that there is no migration of any toxic products into foodstuffs.

Packaging’s main function is to preserve the nutritional values of the packaged food, to protect it from hazardous interactions, whether microbiological, chemical, physical or mechanical, and to attract consumers. Additionally, packaging is the place where the pertinent product information and brand messages are included. Thus, the ideal packaging is the one that fulfills its protective function while developing its potential as a marketing tool. Ink plays a key role in fulfilling both objectives.

UV initiators or photo filters

A basic principle in food packaging printing is that the ink must always be on the side of the substrate that will not touch the contents. We must bear in mind that inks and varnishes are made up of various components which, as already said, cannot be transferred to foodstuffs.

Among the most common components are UV initiators or photo filters, usually belonging to the benzophenone group, which have the function of preventing solar radiation from degrading the colors of the packaging print during its journey through the supply chain and its stay on the retail shelves.

Benzophenone works as a barrier against UV radiation when activated by the UV curing process. The ink printed on the substrate is instantly polymerized and thus protected from the sun’s rays.

Choosing the right material as printing substrate

But not all substrates are completely safe from the possibility of migration of substances from UV initiators or photo filters. This is why it is essential to choose the right material for food packaging if printing on it is required. The barrier properties of plastic and glass, for example, are great, while paper and cardboard need an additional plastic layer to prevent migration.

To ensure consumer safety, EU regulations follow the precautionary principle, even when there is no clear evidence of the toxicity of a given substance. The two main legal references to bear in mind are Regulation (EU) No 10/2011, on plastic materials and articles intended to come into contact with food, and Regulation (EC) No 2023/2006, on good manufacturing practice for materials and articles intended to come into contact with food.

Following assessments by the European Food Safety Authority (EFSA), the European Union sets the allowed limits on the use of substances, such as benzophenone, in inks, varnishes and photo initiators, and establishes the way in which the printing of packaging materials must be carried out in order to prevent contamination of foodstuffs.

Another factor to bear in mind with regard to food packaging is the possibility that, if it is made from recycled plastic or cardboard, it may contain traces of ink. To make sure that there is no migration, it is imperative that the materials have undergone a recycling process to eliminate any previous printing.