Safer Inks Limit Chemical Migration

A 21.7-ounce box of Apple Jacks costs around $3.44 at Walmart. But if your kids’ breakfast cereal smells or tastes odd in the morning, who cares what you paid for it? Imagine taking 28 million boxes of Apple Jacks, Corn Pops, Froot Loops, and Honey Smacks off of shelves nationwide as Kellogg did...


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A 21.7-ounce box of Apple Jacks costs around $3.44 at Walmart. But if your kids’ breakfast cereal smells or tastes odd in the morning, who cares what you paid for it? Imagine taking 28 million boxes of Apple Jacks, Corn Pops, Froot Loops, and Honey Smacks off of shelves nationwide as Kellogg did three years ago. Talk about a brand marketing and public relations nightmare!

The voluntary product recall came in response to about 50 people who called to complain about stale, metallic, and soap-like tastes and scents emanating from the cereal boxes’ plastic packaging; five of them reported nausea and vomiting. Although Kellogg said the potential for serious health problems was low, the manufacturer initiated the recall out of concern that the “uncharacteristic off-flavor and smell” could cause nausea and diarrhea among more sensitive consumers, especially children to whom the products are largely marketed.

Company chemists studied whether a wax-like compound in the packaging may have been the culprit. “It appears that the cereals were packaged in cereal boxes with waxed paper liners that imparted bad taste and odor to the food,” the US Food & Drug Administration (FDA) said in a statement. The FDA added that waxed papers are legal and safe to use in food packaging “but only when they are manufactured and used in compliance with Federal Food, Drug and Cosmetic Act requirements and FDA regulations.”

Although this particular recall was not print-related, per se, package printers worldwide need to be ever mindful of the rules regulating ink and its possible chemical molecular migration onto food products, said Tony Bean field marketing manager at Sun Chemical Corp. “Printers need to realize that the game field is changing, and they need to be proactive to eliminate potential problems,” Bean noted. “It is the brand owners, such as Kellogg’s and Nestle, who are driving this change” because their brand’s reputations are at stake. Like catalogers who dread the expense and hassle of product returns, consumer packaged goods (CPG) companies cannot afford the negative publicity that accompanies product recalls. “It’s even worse in other countries,” he added, citing dramatic television news footage of uniformed police officers in Italy literally pulling Nestle pasta packages from store shelves amid a horsemeat scandal this past February.

Print providers need to use low-migration inks “on all food packaging structures where a risk of transfer of substances from the ink to the packed foodstuff cannot be excluded, ” according to an online blog from ink manufacturer Siegwerk. “Substance transfer can take place via either migration through the substrate or set-off or even vapor phase transfer (which does not even necessitate direct contact of the packaging structure with the packed foodstuff).

It must be understood, the blog continued, that, “a polypropylene pouch in a cardboard box would not be seen as an effective barrier against migrants originating from the printed film on the outside of the cardboard box. Thus, there would be no alternative than use of low-migration inks for such kind of food packaging.” Most of the scandals around printing inks have been related to UV inks because they contained photoinitiators with high migration potential. But water-based, solvent, oil, and other inks used in food packaging must be compliant and checked for migrating substances as well.

5 Years and Counting

Since drupa 2008, finding new food-friendly packaging inks and coatings has become more of a priority among printers and converters as well as their brand-owner customers. Even long-accepted standards and products are being called into question by a steady stream of studies and news reports detailing how chemicals used for packaging can migrate into food, pointed out INX International Ink Co. (Sakata INX Group).

Low migration has become a major issue for ink manufacturers such as Flint Group, INX, Siegwerk, Sun Chemical, and their customers. Some food packaging print/converters find themselves dealing with issues that didn’t directly impact them before. Veteran providers are employing new products and technologies to comply with stringent global governmental regulations and standards as well as additional demands from food marketers. INX’s Jon Graunke, VP of UV/EB technology, and Kevin Facklam, director of regulatory affairs, have served on panels in recent months at PackExpo and the UV Print Conference.

Low-migration inks really are nothing new at Sun Chemical, Bean added, which has been formulating low-odor and low off-taste inks since the early 1980s. “They just didn’t call it ‘low migration’ back then,” he said. Chris Bonk, VP and sheetfed director for INX lent his 21st-century perspective: “There is no question that, during recent years, the focus on packaging has turned noticeably inward. While exterior package ink and coating properties such as brand color fidelity, gloss, rub, and chemical resistance remain key concerns, issues involving chemical migration have dominated the dialog,” Bonk said. “Indirect as well as direct food contact packaging is under the microscope. Every step in the process is being scrutinized, from selection of raw materials for inks to print-production additives such as adhesion promoters and foam suppressors.”

Siegwerk defines low-migration ink as “suitable to be used for food packaging. It will contain only substances that either do not migrate, or other substances in such small amounts that the migration limits, specific and overall, can be met by the final packaging. Of course, every packaging structure is different, and every substrate that is printed has different barrier properties,” Siegwerk continued. “Thus, it is very important to evaluate the real packaging scenario as a whole and to choose the right ink for every scenario.”

At drupa 2012 a year ago, INX and INX Digital highlighted a range of low-migration ink and coating products for flexographic and offset production and sheetfed folding carton food packaging, among other applications. “Due to our global presence and long-term relationships with food marketers and package printers, we have been intimately involved with all aspects of emerging food packaging challenges,” said INX’s Bonk.

Bonk pointed out while government regulations and industry standards protect the food-consuming public, these requirements along with publicity regarding this issue have catalyzed development of advanced package printing products. A number of Sakata INX Group’s low-migration ink and coating solutions were showcased at drupa and also can be seen at the quadrennial PRINT 13 tradeshow in Chicago this September:

  • High performance EcoTech LM sheetfed folding carton inks
  • Energy Curable Low Migration flexographic and offset inks
  • Oil-resistant gas barrier coating material for food packaging
  • Energy Curable Low Migration coatings

Technology and Testing

“INX offerings meet the most stringent standards,” Bonk added. “For example, EcoTech Low Migration sheetfed process color inks are specifically designed for indirect food contact folding carton applications. The EcoTech LM system is formulated without mineral oil, is cobalt-free, and has minimal residual odor. These inks comply with the Nestle Guidance Note on Packaging Inks and conform to U.S. and European food packaging guidelines for outer printing. They also meet ISO 2846-1 standards and are suitable to GRACoL G7 certification.”

Bonk indicated that low odor is a key INX criterion when selecting raw materials, in order to avoid unwanted transfer to the packaging while also avoiding potential health hazards due to chemicals from the graphic process.

“We recommend that low-migration ink testing be performed under actual press conditions,” he cautioned. “This will ensure that a given ink not only meets the single specific migration limit of individual components, but an overall migration limit on all components as well. Of course, it must also comply with brand owner specifications.” Bonk further suggested that brand owners, printers, and converters spell out and publish their respective migration protocols, as Nestle has done with its guidance procedures.

While Nestle has published its own list of “negative chemicals” that either migrate or are odiferous, Sun’s Bean said the FDA makes it very clear that the onus of ink responsibility and testing falls on package printers and converters. “18-point board itself won’t migrate, but there may be concerns over front-to-back contact off a sheetfed stack, for example. Printers can’t turn a blind eye to this anymore,” he warned.

Like many ecological, “green” solutions, low-migration inks do cost more than conventional inks. “Some cost only about five percent more,” said Bean, but others can be double the cost. “UV-curing products are expensive because the photoinitiators are specially made at low volumes,” he explained. “Using bigger molecules drives up the energy costs because you have to use more of them.” Ink manufacturers continue to push, “taking costs out,” he noted, and coming up with economical solutions. “The barrier coating market has been around for a while, but a new twist is developing barrier products for recycled paper board to prevent the migration of mineral oil.

“No-migration inks are coming,” Bean predicted. “Analytical techniques are too good today – they can identify a single atom.” The FDA regulates parts per billion (ppb) – even parts per trillion (ppt) – for poisons or toxicological hazards, Bean pointed out. “One ppb is the equivalent of one drop of water in a 10,000-gallon swimming pool.”

Organoleptic properties are the aspects of food or other substances as experienced by the senses. Organoleptic tests are conducted to determine if package materials and components can transfer tastes and odors to the food in which they are packaged. This is usually done by human tasters. Precise analytical testing is not inexpensive, Bean noted, “but it’s cheaper than lining up 12 [taste] experts.”

Resources

“Low Migration Inks in Packaging,” a guide to help food package providers deal with myriad of challenges, is available from INX International. The publication summarizes the latest, most relevant regulations and standards—including FDA (U.S. Food and Drug Administration) requirements for the U.S., Canada and Europe—plus packaging supply chain links and responsibilities, and practical recommendations for print-production processes. It also includes a glossary of relevant abbreviations and definitions, and a helpful tool for easily interpreting regulations, special precautions and recommendations.

In addition, a Siegwerk brochure entitled “Know How – Customer Guidance: Printing Inks for Food Packaging” contains useful information on food packaging structures and migration risks. Download it here: MyPRINTResource.com/10941207

Also, a 10-page PDF document outlining Nestle’s guidance on packaging inks is available from Xeikon and can be found here: MyPRINTResource.com/10941204

Food-safe Guidance

Jarek Sliwinski, technical development manager at Siegwerk/Environmental Inks, passed along information regarding printing inks for food packaging. Generally, the following parameters may increase the amount of migrants in the ink layer and/or the diffusion of migrants:

  • Drying processes—drying by heat (insufficient drying may lead to increased residual solvents that might migrate)
  • High printing speed—insufficient drying energy (oven temperature, drying air flow)
  • High amount of ink/varnish printed on substrate—insufficient drying energy (oven temperature, drying air flow)
  • Too high amounts of retarder in ink—insufficient drying energy (oven temperature, drying air flow).
  • UV curing—insufficient curing may lead to unreacted monomers and increased photoinitiator amounts
  • High printing speed—insufficient UV drying energy
  • Loss of power of aged lamps—decrease of UV radiation dose at print surface
  • High amount of ink/varnish printed on surface—insufficient drying energy (UV radiation dose at print surface)
  • Addition of photoinitiator and/or acrylate monomer—insufficient drying energy (UV radiation dose at print surface).

Use Care when Printing

The higher the contact surface and the lower the volume/weight of the packed food, the more migrants may end up in the food. Even the type of food makes a difference. Some foods enhance the diffusion of migrants through the substrate/packaging material and/or mobilization of migrants present because of previous set-off. Aqueous, acidic, and/or fatty liquid foods are among the worst. Fatty solid or liquid food in aqueous liquid food, such as mozzarella cheese, also have high uptakes of migrants, as do powdery foods and pastries.

Siegwerk advises against printing additives to make press-ready inks. Also, “inappropriate printing machine cleaning agent substances may carry over to and contaminate the non-printed ink and thus the print,” the firm said. In addition, inappropriate cleaning of equipment in contact with inks, such as rollers and rubber blankets for offset, pose a risk for carry-over if the printer uses the same equipment for inks that are not intended for food packaging. The same is true for fountain solutions.

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