Technology & Science

Milk protein used to make biodegradable food wrap

A new biodegradable film made of milk protein has the potential to keep food fresher and replace plastic wraps, according to researchers from the U.S. Department of Agriculture.

Researchers say food could stay fresher if casein-based film replaces plastic wrap

Cheese slices and cheese string come wrapped in a lot of plastic. What if that wrap was biodegradable, or even edible? (American Chemical Society)

A new biodegradable film made of milk protein has the potential to keep food fresher and replace plastic wraps, according to researchers from the U.S. Department of Agriculture.

Lead researchers Peggy Tomasula and Laetitia Bonnaillie plan to present their work before a conference of the American Chemical Society on Sunday in Philadelphia.

Bonnaillie says the substance they created is made of casein, a milk protein, with the addition of citrus pectin and some salts to make it stronger and more resistant to moisture. It behaves much like a plastic cling wrap, but it's biodegradable, even edible, and there is no danger of harmful compounds leaching into food.

"It feels like plastic wrap, when you look at it and when you hold it, but it does not stretch as much," Bonnaillie, a research chemical engineer with the USDA, told CBC News. She explained that while plastic wrap can stretch as much as 100 per cent, the casein film has about 20 per cent stretch. 
Casein, a milk protein, is being adapted as a film that could be used to replace plastic wrap. (American Chemical Society)

For products such as cheese slices, packaged meat or individually wrapped snacks, it would take packaging that now goes into landfill and replace it with a material that breaks down in the environment.

The film can be folded and sealed around food products. It is as strong as plastic wrap but not as sticky.

Reducing waste

"Applications we are thinking of now are those little single-serve packages that use so much plastic," she said. "If you have children, they love them. It kind of hurts to use them but it's so practical. One possibility is to wrap those tiny snacks with our film."

Bonnaillie also envisages the film could be used to line pizza boxes, so pizza grease doesn't soak through.

"The purpose was to make a packaging that had zero waste," she said.

Would anyone really want to eat the casein cling wrap? Probably not now, as it is currently tasteless, but it could be improved with flavourings.

Tomasula and Bonnaillie work in the dairy research unit of the USDA and hit on the idea of creating a packaging material when they were looking for a use for some of the dry milk that is produced in excess in the U.S. As milk consumption falls, dairy farms have continued to produce too much milk, which is being stored as milk powder.

Excess milk powder

Tomasula "was listening to producers who were asking for something to do with that milk," Bonnaillie said. 

Casein previously has been used in paints, in glue and in some forms of plastics.

The casein film could also help keep food fresher longer, as protein-based films are powerful oxygen blockers that help prevent food from spoiling. As an oxygen barrier, the casein film is 250 times better than plastic wrap, Bonnaillie said. It also has the potential to block light more effectively than plastic.

In spray form, the casein film could be used to keep cereal crunchy, replacing the sugar that manufacturers currently use to stop milk from making the flakes soggy.

Bonnaillie says a small Texas company is already interested in further developing the product, and companies such as Whole Foods have been monitoring their progress as they would like to wrap products in something sustainable.

One drawback — it won't replace the outer packaging, either a cardboard or plastic container that sits on grocery store shelves to keep individual servings clean and dry. It is resistant to humidity but wouldn't stand up if it was immersed in water.