Spray-on Biodegradable Produce Coating Could Replace Plastic Packaging

Imagine if you could buy fresh produce that didn't come swaddled in disposable plastic packaging. Instead, it came covered in a thin gauzy layer of something that could be rinsed off under the tap, revealing a perfectly intact fruit or vegetable beneath. No rotten bits for your compost bin, no added plastic in your trash.

This description is closer to reality than you realize. Last year, a group of scientists from Rutgers and Harvard organized a study and came up with a spray-on antimicrobial and biodegradable food covering that rinsed off with water. It could replace single-use plastic packaging, they said, by guarding against spoilage and transportation damage.

Plastic packaging is a serious global problem. The Natural Resources Defense Council (NRDC) says that 300 millions tons of plastic are produced annually—"nearly equivalent to the weight of the entire human population"—and half of that is for single-use items. A vast majority (91%) does not get recycled (because recycling is largely a myth), but rather ends up in landfills or the natural environment.

The innovative protective coating, described in detail in a study published in the journal Nature Food, was made using pullulan, an edible polysaccharide fiber that the U.S. Food and Drug Administration says is "generally recognize[d] as safe" (GRAS). The pullulan was spun using a technology called focused rotary jet spinning that had previously been used for tissue engineering and was likened by one scientist to a cotton candy machine.

According to a Rutgers press release: "Like the webs cast by the Marvel comic book character Spider-Man, the stringy material can be spun from a heating device that resembles a hair dryer and 'shrink-wrapped' over foods of various shapes and sizes, such as an avocado or a sirloin steak. The resulting material that encases food products is sturdy enough to protect bruising and contains antimicrobial agents to fight spoilage and pathogenic microorganisms such as E. coli and listeria."

The antimicrobial agents include thyme oil and citric acid, both of which are naturally derived, and nisin, a bacterially produced compound used as a food preservative. All are deemed safe for human consumption in the quantities used for this coating.

The researchers used avocados to test the coating, as these fruits are prone to uneven ripening and quick decay. When the time came to remove the coating, it could be washed off in water in a matter of seconds, and was found to extend an avocado's shelf life by 50%. This was likely due to bacteria being unable to infiltrate the coating, thus reducing the rate of natural decay.

Not everyone is convinced it's a surefire solution to the plastic pollution problem. Duke University environmental toxicologist Nishad Jayasundara said he's excited about any biodegradable alternatives to plastic, but that we need to understand more about the rinsing method of disposal, i.e. asking whether this could cause nontoxic materials to break down in potentially harmful ways.

"As a toxicologist," he told Scientific American, "the primary thought whenever you see a newly synthesized product is 'Do we know enough about it?' ... When we first thought about plastics, they were deemed pretty safe molecules. But over time we realized, 'Oh, actually, no, that's not the case.' Now we know that plastics at all levels, regardless of the size, have cellular-level effects, molecular-level effects and ecosystem-level effects."

The scientists behind the spray-on coating remain optimistic. As they point out in the study, the use of micro- and nanofibers for food packaging has been limited up until now due to their reliance on non-GRAS materials and chemical processes. They see this new development as a valuable breakthrough: "This study demonstrates a scalable fibre spinning system for sustainable food packaging technology that enables the one-step synthesis and direct coating of antimicrobial fibres onto fresh foods without further treatment."

While this solution won't work for every kind of food, it's certainly good news for a plastic-ridden world. We need all the help we can get to phase out single-use plastics and come up with alternatives for preserving food to reduce food waste. It will be interesting to see what comes of this particular discovery.