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Coatings protect from mineral oil residues in recycled fibres

By Joe Whitworth+

17-Apr-2014

Recycled fibres in paper packaging can contain mineral oil residues but coatings can protect foods from these substances, according to BASF.

The firm said paper packaging for the food sector can be lightweight, space saving when stacked and be transported cost-effectively.

BASF has developed barrier coatings made from polymers that are applied to the internal surface of the cardboard box.

Only very small molecules like water vapor, can pass. Larger molecules such as mineral oil residues cannot cross and the polar nature of the barriers hinders the migration of the molecules.

Why use cardboard?

Cardboard packaging for food is often produced from recycled waste paper, such as newspapers.

This paper contains residues of newspaper printing inks which include mineral oils not approved for food contact. However, the mineral oils cannot be completely removed in the recycling process and can enter the packaging.  

"Studies by the official Food Safety Authority of the Canton of Zurich have shown that about 30% of all migratable substances have entered the food after two months at room temperature," said Heiko Diehl in BASF’s ‘Science Around Us’ series.

"Once the contaminants have accumulated in the food, they can no longer be removed or made safe by washing or boiling.”

Mineral oils contain hydrocarbon compounds which can travel from the cardboard into the foods.

This can happen without direct contact between the cardboard and the food as some mineral oil residues evaporate at room temperature. This mixture of gases disperses inside the packaging and the substances can be absorbed by the food.

Migration concerns

BASF told FoodProductionDaily.com that a lot of food is already packed into packaging containing sophisticated barriers.

“Here migration of contaminants is not an issue. However, especially dry food packed into pure paper and board, like today normally does, do not require any additional barrier coating,” said Dahl, who is responsible for BASF's Paper Chemicals division.

“Small ambient molecules like water vapor or oxygen can pass the trans missive nature of paper and board. The whole food supply chain for dry food and its quality control are adjusted to this principle.

“Applying now e.g. sophisticated oxygen barrier onto board to prevent migration would interact with the natural gas exchange of dry food with the environment.”

Unavoidable inclusion of recycled materials

Mineral oil residues in foods and their effects are being looked at by the competent supervisory authorities in Switzerland.

Dr Konrad Grob, from Zurich Food Safety Authority, said that the use of cardboard for food packaging is so high that the inclusion of recycled material is unavoidable.

“No legally binding limits have yet been established, only official recommendations. With normal recycled cardboard, however, for most products stored for prolonged periods these values cannot be complied with without a barrier.”

BASF added that specific shelf life tests must ensure that this intervention has no impact on food quality.

“Therefore we developed functional barrier coatings that allow fully e.g. transmission of water vapor or oxygen through the packaging but stop selectively the transmission of especially hydrocarbon based gases or vapors having larger molecule size such as MOSH and MOAH.

“The natural characteristics of paper and board food packaging are not affected by the barrier coating, but our migration barriers eliminate the basic weakness of the trans missive nature of fiber based materials against contaminants.”

Protection length

Barrier coatings that are only 10 to 15 micrometers thick already protect food from the contaminants for up to three years.

This means products like noodles that remain for an average of 15 to 24 months in the packages are protected.

"The most important requirement for the barriers is that the breakthrough time – which is the period until a barrier can become permeable and allow health hazardous substances to penetrate into the food – is longer than the shelf-life of the packaged product," added Diehl.

BASF added paper protects the products against moisture, contamination and damage.

“A fiber based food contact material having a high recycling material content and protection by a migration barrier is a very innovative packaging material and contributes to sustainability by an environmental friendly footprint.

“At the moment we do not see a similar non-fiber based packaging material in the packaging industry.”

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