The study carried out by researchers in Switzerland found that harmful mineral oils from the printing inks used on the cardboard can migrate into food, even if the packaging is used for the corrugated card transport box that holds individual packs.

Tests on experimental packs of fine noodles showed that food rapidly absorbed 10 times the recommended limit for concentration of these contaminating oils from the transport box.

The standard limit for these oils is 0.6mg in each kg of food, but researchers discovered that after standing in packaging for just six weeks, food could contain 6.1mg/kg.

Many dry foods such as rice, noodles, breadcrumbs, cornflakes and muesli are sold in paperboard boxes, where the recommended limit may be exceeded over 100 times. In addition, foods are stored and transported in larger boxes largely consisting of recycled paperboard.

The study found that even if the food was contained in clean paperboard boxes from fresh fibres, printed with inks free of mineral oil and wrapped into a polyethylene film, mineral oils from the corrugated card transport box far exceeded the limit.

Dr Koni Grob, an analytical chemist who headed the research team, said: “There is a tension between the need to recycle paper and board, and the need to keep food free from high levels of these mineral oils.”

Dr Grob pointed to three possible solutions. The first would be to use paperboard made by recycling carefully selected, cleaner starting materials. Secondly, manufacturers could use new wood fibres when making food packaging and transport boxes.

Third, manufacturers could introduce functional barriers against the migration of mineral oil, either as internal bags or lining the boxes with materials such as special plastics.

Some companies have changed their packaging materials to fresh fibre paperboard printed with inks free of mineral oil, but Dr Krob said this did not go far enough.

“They are still using recycled card in the corrugated board transport boxes, which renders their efforts fruitless. In terms of amounts of food packaging material involved, this problem exceeds all those experienced in the past.”

Maxine Perella

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