A study has found that mineral oils from the printing inks used on cardboard can migrate into food if recycled cardboard is used for food packaging.
In tests on experimental packs of fine noodles, researchers in Zurich, Switzerland, found that food rapidly absorbed 10 times the recommended limit for concentration of these contaminating oils from the transport box.
The world-recognised 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.
And this was in food that had a two-year shelf life, so it is quite possible the value could increase further over time.
The research showed 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 (also free of mineral oil); mineral oils from the corrugated card transport box far exceeded the limit.
"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. Koni Grob, an analytical chemist who headed the research team based at the Official Food Control and points out that none of the three presently discussed solutions are easy to put into practice, said.
Many companies have realised the problem and recently some have changed their packaging materials to fresh fibre paperboard printed with inks free of mineral oil.
"But they are still using recycled card in the corrugated board transport boxes which renders their efforts fruitless," Grob said.
"In terms of amounts of food packaging material involved, this problem exceeds all those experienced in the past. It needs to be addressed with corresponding care," Grob added.
The findings were published in the latest edition of Packaging Technology and Science.