The sausages Marit Kvalvåg Pettersen and Tanja Radusin tested last just as long when packaged in recyclable plastic as in complex materials. Photo: Wenche Aale Hægermark © Nofima

Project Year 2018

Food in recycled plastic

 Food safety and quality  

More plastic needs to be recycled, but recycled plastic cannot automatically be used for food. Researchers are trying to change this.

“To be able to use more recycled materials, we need better sorting systems that can separate both different types of plastic and sub-groups within the different types. It is also necessary to check that hazardous components are not transferred from the plastic to the food,” says Marit Kvalvåg Pettersen, a senior scientist at Nofima.
The majority of households in Norway source sort plastic. Designing better recycling systems must therefore be based on knowledge about the types of plastic in Norwegian households.

Necessary to separate different types of plastic

For seven weeks, 60 households collected all their plastic waste and delivered it to the research project FuturePack. This amounted to roughly 60 kg of plastic. The waste was washed and sorted into five categories: PP (polypropylene), PE (polyethylene), PS (polystyrene), PET (polyethylene terephthalate) and other plastic (either unlabelled or a combination of several types of plastic).
“PP was the largest category, so we chose to concentrate on this and further sort this type of plastic into subgroups. Another important reason for the focus on PP is that different types of PP are used in different processing methods,” explains Tanja Radusin, a post-doctoral researcher in FuturePack. During the first year of the project, she has concentrated on materials and has been stationed at Norner, which is leading the project.

Migration analysis to check that food stays safe

Materials used in food packaging must be guaranteed safe. The transfer of components from packaging to food is called “migration”. The researchers have compared certain types of recycled plastics with new, virgin plastics. Migration of components must be under defined threshold values.
“We have tested ten different qualities of plastic in harsh conditions and different temperatures to determine whether chemical components migrate from the plastic to the food. As expected, there is a clear correlation between temperature and migration. The higher the temperature, the more migration there is,” says Tanja Radusin.

Seven recycled and three virgin

Migration analyses were performed on seven recycled and three virgin types of plastic. Virgin plastic intended for contact with food is safe, but there were large differences between the recycled varieties.
“Some recycled plastics cannot be used for food packaging, while others seem promising. Based on the tests, we see that more detailed sorting is a prerequisite for being able to use recycled plastic in food packaging,” concludes Marit Kvalvåg Pettersen.

Facts about plastic

There are many types of plastic qualities. The most common main categories found in Norwegian households are described below.

• Polypropylene (PP) comes in both flexible and rigid variants that can also be applied high temperatures. It is used for bottles and packaging for fresh meat and ready meals that are to be heated in a microwave oven. Flexible PP is used widely in packaging for vegetables.
• Polyethylene (PE) occurs also in different varieties, from very soft and flexible to completely rigid. PE can be used in many applications from plastic wrap (bread bags, carrier bags) to bottles, bowls and cups.
• Polystyrene (PS) is transparent, rigid and fairly brittle and has a relatively low melting point. Disposable glasses are often made of PS. PS is also often used for dairy products, such as yogurt.
• Polyethylene terephthalate (PET) is strong, rigid and easy to recycle. Plastic drinks bottles are usually made from PET.

Many products can be made of several different types of plastic. What determines what type of plastic manufacturers choose is what the plastic will be used for, how long it will have to last, and how robust it needs to be.

Norner, the Paper and Fibre Research Institute (PFI), Østfoldforskning, the Department of Chemical Engineering at NTNU and participating companies.)

The Research Council of Norway and participating companies

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