Researchers from the Fraunhofer Institute for Process Engineering and Packaging (IVV) and Albstadt-Sigmaringen University have created a prototype of an almost entirely bio-based, thermoformable multilayer film for packaging food under protective gas.

According to its developers, the packaging is derived from bio-based polylactide (PLA), soy protein and sunflower wax and was developed under the "PLA4MAP" project.

Sensitive foods, such as fresh meat, sliced sausage or cheeses products, for instance, typically need to be packaged under a protective gas atmosphere to prevent the growth of germs as well as to extend the shelf life of the product. To maintain such an atmosphere for a long period of time, the packaging materials must possess gas barriers, which many currently available bio-based packaging does not.

As such, the researchers created a tray composed of a four-layer composite material under project "PLA4MAP." The four layers feature one thin protein layer of soy protein concentrate, which serves as an oxygen barrier; a thin wax hot-melt layer to serve as a water vapor barrier; and two PLA cover layers that surround the oxygen and water vapor barrier layers.

The team used sunflower seed wax for the wax layer because it is a by-product of edible oil production. Meanwhile, the sealing film was also based on PLA but enhanced with metallization.

The team added that the composite material fulfills all the barrier properties required of such packaging and only the inorganic layer of the lid film and segments of the wax hot-melt layer are not sourced from plants.