Wrapping food in plastic can reduce spoilage, but there are some big downsides – for a start it doesn't work all that well, and it creates waste that can clog up landfills and our oceans for years. Biodegradable alternatives like chitosan and essential oils have been studied as potential replacements, and now scientists have used the milk protein casein to create a packaging film which is degradable, edible and much better at preventing spoilage than plastic.
Coming out of research from the US Department of Agriculture, the casein film has much smaller pores than existing packaging options, which reportedly makes it up to 500 times better than plastics at locking out oxygen. Besides reducing waste by increasing the shelf life of food, the milk protein base also means the packaging will biodegrade quickly when thrown out, or can just be eaten along with its contents.
"The protein-based films are powerful oxygen blockers that help prevent food spoilage," says lead researcher, Peggy Tomasula. "When used in packaging, they could prevent food waste during distribution along the food chain."
During early attempts at developing the packaging, the researchers used pure casein, and while they found it to be effective at blocking oxygen, the resulting material wasn't very flexible and tended to dissolve too quickly in water. To combat this, the team added citrus pectin, which has been used in other edible coatings, to make the film more durable and increase its resistance to heat and humidity.
Being edible, the casein packaging will still need to be wrapped in protective outer layers to keep it dry and clean, so while it might not completely replace plastics, it could significantly cut down on the amount used.
"The coatings applications for this product are endless," says Laetitia Bonnaillie, co-author of the study. "We are currently testing applications such as single-serve, edible food wrappers. For instance, individually wrapped cheese sticks use a large proportion of plastic — we would like to fix that."
A sprayable version may open up further applications, such as keeping cereal crunchy in milk – a much healthier alternative to the current method of coating it in sugar. It could also be used as a laminate-like barrier between food and its packaging – keeping pizza boxes from getting greasy, for example. With the US Food and Drug Administration (FDA) recently tightening the use of existing perfluorinated grease-proofing agents, the researchers suggest casein may provide a safe replacement.
While a milk-protein-based packaging has clear advantages over petroleum-based plastics, it's worth noting the dairy industry is itself not without environmental impact, which may make other biodegradable packaging based on waste materials like crustacean shells and fruit peels a more attractive alternative.
The team is continuing to improve the casein packaging and is currently producing samples of the film for a Texan company. The hope is to have the material on the market in the next three years. The research is being presented at the 252nd National Meeting and Exposition of the American Chemical Society this week.
The team describes the casein film in the video below.