How to select inks for food packaging?

Let us first look at categories with migration risk

The following table gives a non-exhaustive overview on the major packaging categories with risk of migration, set-off and/or organoleptic deterioration, as well as recommendations with regard to the selection of ink types and validation measures by the printer.

In case of packaging with an identified migration risk, only inks and varnishes explicitly intended for food packaging should be used.

Special attention must be paid to applications subject to high temperature exposure, such as pasteurisation, sterilisation (dry or in an autoclave), microwave or baking oven. To prevent migration of cleavage products from certain yellow, orange or red pigments, selection of special ink shades, based on appropriate high-performance pigments, may be required. This applies especially if the packed food will be subject to more than 200 °C in a microwave or baking oven; equally a particular choice of alternatives is necessary if food is to be boiled, pasteurized, sterilized, or cooked in a microwave or baking oven, and is packed in structures which do not provide a functional barrier to migration.

A printer should additionally use the checklist: “Processes and Parameters which potentially trigger non-compliance [sic] (migration, organoleptic effect)” for verifications (see article Compliance: Ink migration in food packaging). Packaging intended for particularly sensitive consumer groups (such as infants and small children) requires formal qualification in any case.

Categories without migration risk

Cases of unintentional and intentional direct food contact

Particular cases of unintentional but foreseeable direct food contact of the printed ink layer

There are cases where unintentional but foreseeable direct contact of the printed and dried or cured ink and/or varnish layer to the food is possible. This is associated with a higher risk for the consumer as there is no barrier function of the packaging material between ink and food.

Some examples:

Lamination print job where the printed layer may be exposed to food at the cutting edges, or

a packaging line where wrappers of food packages are partly folded so that a small area of the printed surface is turned inside (e.g. butter wrappers), or

food that could be spilled onto a surface print upon opening of the package by the consumer (who may lick it off), or

articles with transient food contact like napkins, placemats, tea tags and others.

In accordance with Good Manufacturing Practice principles, Siegwerk recommends precautionary measures to the converter to minimize the risk of migration. Otherwise, colored matter could end up in food (so-called ‘bleeding’), and/or non-visible migration could occur via solubilization of the printed layers. To prevent any risk of bleeding and solubilization, the resistances of the printed layers to the relevant foods are to be guaranteed as measured by the relevant fastness standards:

 ISO 2836 (Assessment of print resistance to various agents; in particular with regard to water, oils and fats, cheese and spices),

ISO 11628 (Determination of print resistance to acids)

EN 646 (Paper and board intended to come into contact with foodstuffs – determination of color fastness of dyed paper and board) for towels and napkins.

The printer is responsible for the selection of printing inks and varnishes which are resistant to the respective foodstuff. To the extent that the information is not already declared in Siegwerk’s Technical Data Sheets and related documentation, the required typical fastness data is available on request. As a further measure, Siegwerk recommends the assessment of potential migration of the relevant migrants via a worstcase calculation or – preferably – via a practical migration test.  

Direct food contact applications

In the vast majority of food packaging structures, the printing ink is applied to that side of the packaging which is not in direct contact with the packed food. But there are some instances with intended direct food contact of printing inks (or protective coatings, heat-seal coatings, anti-fog coatings or slip coatings). It is obvious that in comparison with non-food prints there is a massively increased risk of migration into the food.

In Europe, today, in the absence of specific legislation concerning printing ink products intended for direct food contact, only raw materials are used that are included in positive lists and/or have been evaluated by a recognized expert body. However, the situation is about to change: the German Ordinance on Printing Inks will provide a positive list of substances that are allowed to be used for direct food applications as long as the given migration limits are met.

Under FDA provisions, direct food contact refers to a printing ink or coating (e.g. protective, sealing, antifog, slip lacquers) that is intended by design to be in direct contact with a food product. By virtue of this intimate contact, components of the printing ink or coating have the potential to migrate to food and, therefore, must be in compliance with the indirect food additive guidelines at 21 CFR Parts 173-178. Indian Standard IS 15495 addresses also printing inks and varnishes for direct food contact. It is stipulated that, “if for some specific requirements it is necessary for the printed surface to be in contact with food, the printing inks shall be formulated with materials which are acceptable as food additives” and “produce a non-toxic printed surface that complies with the appropriate regulations”.

In any case, for such critical DFC applications, the printer is advised to use only designated inks for intended direct food contact and to safeguard with great care that no inacceptable migration takes place under the foreseeable conditions of use.