A project to develop bioplastic packaging that helps extend the shelf life of food and displays when food is no longer fit to eat is being co-ordinated by Norwegian research organisation Sintef Materials and Chemistry (www.sintef.no/en/sintef-materials-and-chemistry). Nanoparticle components have been added to the biopolymers to provide the packaging with improved food preservation properties, while a sensor can detect, for example, whether the temperature of the food has become too high or if a product has soured, says Sintef.

The packaging is designed to protect the contents from their surroundings and thus extend shelf life, says Åge Larsen, a senior research scientist at Sintef. “We achieve this by means of improved oxygen barriers. Standard plastic packaging allows the entry of air which places restrictions on shelf life,” he adds. The first materials to be developed under the project, which was launched four years ago, are made of PLA and bio-PET.

Four prototypes have been developed. Portuguese rigid packaging producer Logoplaste (Cascais; www.logoplaste.com) has developed, in collaboration with Sintef and other research partners, a blow-moulded bottle, while Greek rigid packaging producer Argo (Athens; www.argo-sa.gr) has developed a pot designed to hold seafood such as crabs and prawns. Both types of container are covered with an oxygen-proof exterior coating developed by Sintef.

In addition, a three-layer coating has been developed consisting of a cellulose-based film sandwiched by two biodegradable polymer layers that serve as oxygen barriers. This can be used in the same way as the rigid plastic currently used as food bowls, Sintef says. The fourth prototype is a blow-moulded film that is essentially plastic foil similar to that used to make plastic bags and as oxygen-protective coverings for plates containing food.

The packaging contains a sensor that notifies retailers and consumers when the food inside is no longer fit to eat. One type of sensor consists of nanocapsules containing signal substances. If the temperature becomes too high or the pH value anomalous, the capsule shells decompose and release the signal substances. "The sensors are sensitive to small changes and the packaging will change colour when the substances are released," explains Larsen. He notes that it could be embarrassing for a food retailer to be faced with rows of red flashing lights, “so we envisage developing substances that are not necessarily visible to customers when they are released. Manufacturers, on the other hand, will be able to use direct-reading instruments."