Ink specifications and migration limits are vital
Food manufacturers need to be clear about the printing inks they specify, say ink suppliers, and the European Commission (EC) needs to lay down realistic migration limits for sensitive chemicals.
Incidents involving the transfer of inks from the outside to the inside of the pack (also called set-off) have prompted a flurry of activity from, among others, the EC. Says Dr Erich Frank, head of technology management at ink manufacturer Flint Group: "The authorities have understood that specific legislation for printing inks was required. But no one knows when the legislation will emerge, or what form it will take."
One major industry concern is that the EC will set a zero level of chemical transfer. That will simply be unworkable, says Frank: "We need clear definitions and maximum permitted levels, as you have with plastics additives."
Flint is a member of the European Printing Inks Association, which has published its own guidelines for Good Manufacturing Practice with regard to ink handling and printing. But Frank, who specialises in inks for the offset litho process, adds: "Communication among suppliers, print shops and food manufacturers has to improve. The print shop will tend to use the cheapest standard ink, where possible." Unless the food company specifies and defines the inks it requires, potentially dangerous situations can still arise, he argues.
Just over two years ago, Nestlé baby milk products were hit by a crippling recall in southern Europe. Traces of the ultraviolet (UV) photoinitiator isopropyl thioxanthone (ITX) had been detected inside the Tetra Pak cartons used.
In this case, set-off happened when the printed material was wound on a reel. Frank explains: "Print operators have to ensure that the ink is absolutely dry before this kind of contact can happen, and they need active quality control to verify that no transfer has taken place." Solutions could include a zigzag-style arrangement post-UV curing, or interleaving a buffer material in the reel.
