Evaluating Food Contact Declarations for Paperboard Barrier Coatings
Evaluating paperboard barrier food contact declarations requires verifying specific migration limits, functional barrier continuity, and total NIAS disclosures.
Ink Set off Migration
Contact Transfer
Unintentional transfer of printing ink components from the printed outer surface of a sheet or web to the unprinted food-contact surface occurs when the material is stored in tightly compressed rolls or stacks. This ink set off migration represents a major risk for food packaging converters, as chemical compounds like photoinitiators or plasticizers can contaminate the food-contact side before the carton is assembled. The process occurs during the storage period between printing and converting, without any physical damage to the paperboard itself.
It is distinct from gas-phase migration, relying entirely on the direct physical contact between the two surfaces under pressure.
Stack Pressure
Pressure distribution within a printed pile or a tightly wound reel accelerates the molecular diffusion of mobile ink components across the interface. Heavy ink coverage and slow-drying ink formulations exacerbate the phenomenon, as the wet or semi-cured ink film remains highly receptive to transfer. Adjusting the spray powder application or utilizing ultraviolet-cured inks with low-migration properties helps minimize this molecular transfer.
Barrier Shield
Packaging designs can mitigate the risk by incorporating functional barriers or unprinted margins. A protective overprint varnish can lock the ink film in place, preventing it from contacting the adjacent surface. This protection is required when packaging fatty or dry foods that are highly sensitive to chemical taints.