Digital Print for Food-Safe Packaging
Consumers have more choices than ever. Boutique brands, regional providers, and craft products fill shelves and generate demand for packaging. Print providers eyeing this market face unique challenges, including food safety.
The term “Low migration” (LM) in the ink market is linked to packaging compliance and the production of indirect food contact packaging, where the foreseeable use does not result in direct contact between foodstuff and print.
The digital printing industry finds itself under scrutiny, given the growing prominence of digital print for food packaging. With the potential to achieve scale, image quality, and running costs rivaling conventional technologies, inkjet printing holds particular promise. Not surprisingly, the next generation of presses has been developed with compliance in mind.
Migration and what to do
In simplest terms, ink migration is the transfer of unwanted substances from the printed surface to the product.
Migration results from four primary causes: diffusion, set-off, vapor phase, and condensation extraction. Each presents unique challenges.
Packaging safety is determined by substrate type and thickness, ink laydown and print coverage, end-use conditions, and the foodstuff itself. Each step of the manufacturing process impacts compliance, including package design.
Converters install controls on press to prevent non-visible set-off, and ensure full ink and varnish curing and drying. For water- and solvent-based inks, any residual solvents and volatile substances can be controlled. For UV-curable inks, full curing must be assured.
For example, Screen’s (Booth 10951) Truepress Jet L350UV+LM UV inkjet press features inks and a nitrogen purge mechanism to reduce extractable ink components, and mitigate diffusion migration risks. Because oxygen interferes with the curing process and prohibits full polymerization, nitrogen is used to purge oxygen, and sensors shut-down the press when it is detected.
Ultimately, ink innovation ensures packaging compliance. Because UV inkjet ink’s nano-sized Initiators and monomers can penetrate general packaging when insufficiently cured, Screen’s LM ink works with the nitrogen purge mechanism to accelerate and deepen UV curing, minimize odors, and eliminate impact on food flavor. Third-party testing laboratory Triskelion (TNO) in The Netherlands have certified these results.
Testing shows Screen’s LM inks can be used without migration risk with a PET layer greater than 25 microns, or a 40 micron PP barrier for non-fatty dry food. Additionally, functional barriers prevent migration in use and during processing.
Non-print factors may also affect chemical migration from contact materials to food. Subsequently, testing laboratories work closely with ink manufacturers. Screen, for example, has worked with laboratories TNO and Swiss Quality Testing Services (SQTS).
Legislation and conclusion
Regulations vary globally. The European Printing Ink Association (EuPIA) provides enhanced Good Manufacturing Practices (GMP) guidelines for varnishes, coatings, and inks. The USFDA regulates food contact materials with the basic assumption that packaging materials will infiltrate food unless documented testing proves otherwise. Nestle Guidance Notes are widely revered as global industry benchmarks.
Ink manufacturers work with these agencies to document compliance. Screen’s LM Inks comply with the EuPIA’s Exclusion Policy for Printing Inks & Related Products (December 2018), Suitability List of Photo-Initiators for Low Migration UV Printing Inks and Varnishes (February 2013), and Good Manufacturing Practice (GMP) Printing Inks for Food Contact Materials (March 2016). It has also received positive list on Swiss Ordinance (SR 817.023.021 Annex 6, 10); and the Nestle Guidance Note on Packaging Inks (August 2016).
Ultimately, packaging manufacturers bear responsibility. Compliant solutions are a result of design, materials, construction, process, and product. Choosing the right OEM partner is the first step in demystifying these challenges.