New plant-based plastic offers opportu­ni­ties for food sector

Biobased plastics are advancing rapidly, but practical use remains challenging. A material must be strong, resist moisture and break down after use. Researchers from Wageningen, Amsterdam and China have now taken a new step. They developed a plant-based plastic that combines these properties. The results were published in Nature Communications.

Protein from corn

The new material was named plantymeer. The researchers made it from zein, a protein from corn. This protein has been known for decades as a raw material for fibers and bioplastics.

To make plantymeer, the researchers dissolve the protein in ethanol and water. They then bring the mixture to a tipping point. This creates a thick, viscous protein phase. PhD candidate Yijie Wang pressed it through a small opening. He also rolled the material out over a flat plate. After drying, this produced fibers and film.

According to Renko de Vries, associate professor of Physical Chemistry and Soft Matter, the key change happens during this processing step. The mechanical force changes the structure of the protein chains. This creates crosslinks, without chemical additives. The result is a plastic that is stronger than widely used polyethylene.

Better resistance to water

Moisture remains a difficult issue for bioplastics. Plantymeer performs better in this respect than soy-based plastic. After one hour underwater, the film had absorbed 25 percent of its own weight in water. For soy-based plastic, that figure is 175 percent. PET, at no more than 0.1 percent, still performs clearly better.

Most of the material breaks down within four weeks. According to the researchers, this leaves no microplastics behind.

Not a packaging material yet

De Vries mainly sees opportunities in agriculture. In that sector, biodegradability often matters more than top-level performance. Wouter Post, a researcher in sustainable plastic technology in Wageningen, also sees potential for disposable products. He cites plastic cutlery, plates and straws as examples.

Further research is needed before the material can be used in packaging. So far, the Chinese researchers have made around one square meter of film. Scaling up appears technically feasible, but corn protein is a bottleneck. “Proteins are valuable and compete with food or animal feed,” says De Vries. That is why the researchers are also looking at feathers from the poultry sector and residual streams from beer production.

Wur.nl