Muller Martini says the variable sleeve offset printing (VSOP) variable web printing press is viable for food contact applications.
“For all of our packaging materials, we require our printers to use only printing methods that are designed for food contact applications,” says Dr. Stéphane Papilloud, packaging group manager, quality & safety department, Nestlé Research Center in Lausanne, Switzerland.
That means that there cannot be any harmful effects on human health or any unacceptable changes to the organoleptic characteristics of the product (detrimental effects on smell, taste, color or appearance).
Everything must comply fully with all relevant statutory regulations of the country in which the products are sold.
The producers of packaging materials have to demonstrate their compliance with Nestlé’s requirements – both physical, such as artwork, and chemical, such as migration values, as well as sensory harmlessness of the printed packaging materials.
In-house standards
In addition to the legal requirements imposed, for example, by the European Union, the US Food and Drug Administration and the Chinese government, Nestlé has stricter standards for food packaging, for instance for the printing of the inside and outside of packaging and for ultra-violet (UV) inkjet printing and residual solvents.
“We always keep our suppliers updated about those requirements,” Papilloud says.
She was impressed by electron beam inks.
“It’s a good technology that does not require photo-initiators, so that there cannot be any resulting migration. However, the principles of low migration potential and low odor must also apply to the rest of the printing ink formulation such as acrylates resins, oligomers and additives.”
Environmental goods
Since the costs of compliance with extensive environmental requirements (exhaust air treatment and explosion prevention) do not apply due to the use of UV or electron beam printing inks, the environmental factor is one of the three major advantages that the web offset printing method offers for food packaging, explains Bernd Sauter, MD of Muller Martini Printing Presses GmbH, Germany.
“There are neither residual inks nor residual solvents, and neither are explosion-proof storage for inks and solvents nor a wash-up system for machine parts, cylinders and inking rollers required. That leads in total to far lower insurance costs for a production site.”
Growing range of substrates
Sauter notices a growing range of printable substrates.
“Until a few years ago, certain substrates such as polyethylene could not be processed or required special knowledge of the complex printing process. Today, advances in technology enable the stable and reliable printing of such substrates using web offset,” he says.
Whether it be the thermoplastic synthetic material polyethylene, polylactic acid consisting of corn starch, or stretch sleeves, which are increasingly widespread thanks to the new web tension regulation on the VSOP variable web printing press, cooperation between Muller Martini and suppliers is contributing considerably to new substrates establishing themselves increasingly quickly, Sauter explains.
Another example is low density polyethylene (LPDE), used by another of Muller Martini’s European customers for printing.
The LPDE foil feels softer and thicker, has lower density than a traditional foil made from high density polyethylene and barely rustles.
These qualities enable the packaging of frozen foods.
