Mineral Matters

29 September 2020

Over the past decade, mineral oil migration has brought the food packaging industry some of its most damaging headlines. Have we learned our lesson, or will the same hold true for the 2020s? Tim Gunn asks food chemist Dr Ulrich Nehring about the issue and the development of best practices to deal with it.

It started with newsprint. Your paper’s repackaged stories were recycled into packaging, and into that packaging went your food. No one realised it was meant to be an exchange, but in 2011 dailies and weeklies across Europe flipped the supply chain, tearing their stark black serifs straight from cereal boxes, which, so they announced, could cause cancer.

Those headlines were made of mineral oils – more or less refined, and, depending on how they’re encountered, more or less harmful, petroleum products. Researchers in Switzerland had begun to detect worryingly high levels of non-food-grade ones in foods packaged in recycled paper. The prime source was newspaper ink.

And so the war on mineral oil hydrocarbons (MOH) migration began in earnest. Other types of migration may have made headlines more consistently, but only one has prompted the re-evaluation of the worldwide food supply chain in the decade since. The packaging industry has now established a robust set of best practices around using vegetable-oil-based inks and functional barriers against migration, but, as recently as 2017, Dutch cheese biscuits were recalled from the market because of their incredibly high levels of mineral oil contamination.

What’s more, from a scientific and regulatory perspective, the issue is humblingly complex: although it was first studied in the early 1990s, we still don’t have a good way to measure MOH migration. Each mineral oil is less a particular substance than a unique and complex blend of distinct chemicals – different hydrocarbons with different chemical structures and molecules of different weights and sizes, each of which could migrate or impact humans differently. Even the most expensive toxicological and analytical tools are incapable of accurately tracking so many variables. The traditional test can only give an approximate quantity for the sum of all the components in a particular blend. A second tool can be used to establish some of the possible sources of the different hydrocarbons, but it gives absolutely no indication as to the quantities in which they are present.

“We know some of the typical components of mineral oil hydrocarbons, and we know that there are, for instance, potential carcinogens, but for many of the components in such a blend, we do not have any clue about their safety,” points out Dr Ulrich Nehring, a food chemist and consultant to the metal packaging industry, as well as the former scientific director of the Institut Nehring food testing laboratory (now a part of Eurofins). “That, in fact, is the whole issue – we do not really know how to evaluate these blends, and so the legislator does not have a clear idea about how to set a limit for them. A legal limit is usually based on toxicological evaluations, and this is not possible here.”

Trials and errors

What chemists like Nehring can say is that there are two general types of MOH: saturated (MOSH) and aromatic (MOAH). It’s known that the smaller aromatic fraction of an MOH blend can contain carcinogens (and, accordingly, it was this fraction that accounted for the most lurid headlines in 2011). As yet, there is no evidence of carcinogens in the saturated fraction, which typically makes up about 80% of a given mineral oil. Elements of MOSH have been shown to accumulate in human tissue, but, as Nehring puts it, “accumulation is not a toxicological end point, and we don’t fully know its effects”. If this is beginning to sound at all straightforward, note that the way MOSH chains and MOAH ring structures are differentiated depends on the tools one uses to identify them. Those used to investigate migration typically record some saturated chains in the MOAH fraction.

Equally, as scientists can only estimate the quantity of MOSH and MOAH in foodstuffs, the whole enterprise is beset with error. The same product can be tested in two different laboratories and produce two different results. Since 2017, the analytical technique for quantifying MOSH/MOAH in certain foods has been standardised across Europe, but Nehring is quick to point out that the technique is far from perfect, and that the comparability of analytical results is still “very, very poor”.

That’s today. In the immediate aftermath of the Swiss study, when tools and tests were even less refined, numerous brands and retailers felt they had no workable option but to rethink their commitment to a circular economy.

“You have to keep in mind that there are contradictory interests in this whole story,” says Nehring. “On one side, we are all asked to use as little fresh paper as possible and to recycle all packaging material. On the other hand, retailers who pretend to be green and environmentally friendly can just ask their suppliers not to deliver any food in recycled paper packaging – of course, it’s an ecological disaster if large retailers do this, but they did it in the past.”

Not that it was much of a solution. Even when brands used fresh-fibre primary packaging, MOHs kept showing up in their foods. The more volatile hydrocarbons from recycled transport boxes were still evaporating, passing through all the intermediate layers and entering food as gases. There was a delay before this became apparent, and after it did some brands tried to exert more control over transport boxes. Now, however, most have given up on such uncompromising and ecologically damaging requirements. “They’ve realised that it is, in fact, impossible to deliver everything in fresh fibre paper,” says Nehring. “It’s impossible.”

The problem persists

Other solutions proved more achievable. Before long, cleaning and recycling processes had been refined, and effective plastic and foil barrier layers developed to keep potential carcinogens out of foodstuffs – a particular challenge given the aforementioned variety of MOH blends. In Europe, most newspapers even shifted to using vegetable oils in their inks; and still the MOH kept coming.

After a regrettable 2012 Christmas season, during which the prevalence of MOH in advent calendar chocolate put it back in the headlines, the German confectionery industry (BDSI) moved to take control of the narrative. Advent calendars were a particular problem because brands outsourced the production of their packaging to specialists, but even after that had been addressed, the industry continued to investigate how MOH was getting into its food and began to develop a toolbox for keeping it out.

190 mg/kg
The highest measurement of potentially carcinogenic mineral oil aromatic hydrocarbons found in Dutch cheese biscuits recalled from the market in 2017.
Food Packaging Forum

What chocolatiers realised was that the levels of MOSH/MOAH in their products remained troublingly high even when there was no possibility of either migrating from packaging materials. That is, apart from the jute sacks used to store and transport the raw cocoa beans in and from their countries of origin, which are treated with mineral oils to increase their flexibility and moisture-resistance. But even when cocoa beans were picked and transported without contamination (and not, for instance, dried on asphalt), chocolate products were shown to contain MOH. Of course, none of those products could exist without machines, and machines need lubrication. Lubricants, it goes without saying, are made with mineral oils.

0.5 mg/kg
The maximum limit for mineral oil aromatic hydrocarbons in draft German legislation.
Food Packaging Forum

Then again, even apples have a natural wax outer layer made of saturated hydrocarbons that most analytical tools wouldn’t differentiate from MOSH. Moreover, numerous important food additives and components of food contact materials like paraffins are ‘MOSH-analogues’ also derived from mineral oils, which are common ingredients in baby oils, cosmetics and ointments, too. Then there are polyolefin oligomeric saturated hydrocarbons (POSH) and other MOSH-like structures derived from plastics, which can migrate into food from the very barriers used to prevent MOSH/MOAH doing so.

2.2 mg/kg
The average concentrations of mineral oil aromatic hydrocarbons found in food on the German market in a 2011 Swiss study.
Food Packaging Forum

It’s here that the idea of a toolbox based on the British health and safety principle of ‘as low as reasonably achievable’ (ALARA), rather than a legislative limit, proves its value. The work started by the BDSI has since been adopted by the German Federation of Food Law and Food Science (BLL), and Food Drink Europe (FDE). Nehring was part of the BLL working group that adapted it for use in other industries besides confectionery, and continues to work on refining and updating it. The pithily titled ‘Toolbox for Preventing the Transfer of Undesired Mineral Hydrocarbons into Food’ is available from the FDE website.

“I think the industry has accepted that you need to apply the ALARA principle, but it is difficult to prove this by analytical tools, and it is impossible to regulate it by legal limits,” Nehring explains. “Nobody really wants to tackle this on a political and legal level because it’s a minefield. You get lost. It’s quite impossible to differentiate the quantity of contamination coming, for instance, from a polypropylene bag, and mineral oil contamination coming from machine lubricant. And from a legislative point of view, it’s very difficult to reason why the saturated hydrocarbons coming from mineral oils are treated differently than almost the same chemical substances coming from a polypropylene bag. How do you explain that to consumers?”

A regulatory nightmare

As such, attempts in Germany to pass an ordinance restricting MOAH levels to 0.5mg/kg in food products have repeatedly failed, and seem to have been abandoned. Tellingly, there’s no scientific basis for such a limit, as any level of carcinogenicity can cause cancer. Instead, the figure is based on the fact that chemists and toxicologists cannot safely or reliably detect, or quantify, lower concentrations. The standard test recommended in the FDE industry toolbox is only suitable for MOSH and MOAH concentrations above 10mg/kg each in food based on vegetable fats.

“Nobody’s really tackling this issue on a legal level, because it’s a disaster, a legal disaster,” Nehring continues. “You don’t have toxicological proof for any limits, and you don’t have the safe and reliable analytical tools to enforce such a law.” Nevertheless, a number of retail companies in France and Germany have instituted their own rules for MOSH/MOAH levels in the products they sell.

Nehring is more supportive of the European Commission’s 2017 decision that member states should monitor the levels of mineral oil hydrocarbons in their food. Still, as the only countries with laboratories capable of carrying out such tests are Germany, Switzerland and Austria, it’s yet to have any real effect.

That said, Nehring believes the issue of MOH migration has already changed packaging for the better. “We still have this problem that mineral oil hydrocarbons may contaminate food,” he says, “but mainly from other sources. There may be some sources that we haven’t thought of yet, but the packaging material itself is no longer the problem.”

At the same time, the growing acceptance of the applicability of the ALARA principle reflects a more realistic understanding of the fact that humans have to live with carcinogens. “We’ve known for decades that, for instance, if we fry or grill our food, we will find some carcinogens in it,” Nehring sighs. “But if we do not fry our meat, or grill it on a barbecue, we do not really like it. That’s the nature of our food. The better it tastes, the worse it is for our health. And, as a food chemist, I have to say that this is not news.” 

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