Web offset: a boon for package printing for the food industry

Slightest migration of inks can turn into a major disaster for package printers to meet the high demands of food producers and here comes the VSOP variable web printing press from Muller Martini lets printers meet these challenges. “For all of our packaging materials, we require our printers to use only state-of-theart printing methods that are designed for food contact applications,” says Dr Stéphane Papilloud, packaging group manager, Quality & Safety Department, Nestlé Research Center in 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, colour or appearance), and that 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. “That’s why Nestlé only considers suppliers that can meet our commercial and technical requirements in a sustainable way,” Papilloud says.

In-house standards
In addition to the legal requirements imposed, for example, by the European Union, the US Food and Drug Administration or the Chinese government, Nestlé sets its own, stricter standards for food packaging, for instance for the printing of the inside and outside of packaging and for UV inkjet printing and residual solvents. “We always keep our suppliers updated about those requirements,” Papilloud says.

The expert from the global corporation is 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, managing director 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
According to the printing press expert from Muller Martini, there is another important benefit of web offset: the growing range of printable substrates. “Until a few years ago, certain substrates such as polyethylene could not be processed or require special knowledge of the complex printing process. Today, advances in technology enable the stable and reliable printing of such substrates using web offset.”

Whether it be the thermoplastic synthetic material polyethylene, polylactic acid (PLA) 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, good cooperation between Muller Martini and suppliers is contributing considerably to new substrates establishing themselves increasingly quickly, Sauter explains. Another example is LPDE (low density polyethylene), 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 HDPE (high density polyethylene) and barely rustles. Due to these specific qualities, it is ideally suited to the packaging of frozen foods.