Nature's Own Packaging: How Plants and Insects Coat and Protect Themselves

Field report

Waxy cuticles, resinous sap, and chitin armor do the job without a scrap of plastic.

Katherine Martinko is an expert in sustainable living. She holds a degree in English Literature and History from the University of Toronto.

Plastic packaging is a serious global problem. The Natural Resources Defense Council (NRDC) says that 300 million 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.2

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).3 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.4

Nature, however, beat scientists to the punch by eons. Step outside and run your fingers across the leaf of a rubber tree or a magnolia — the waxy sheen you feel is cutin, a polymer that plants secrete to seal in moisture and block pathogens. It is remarkably similar in function to what the Rutgers team created. Some desert plants, like the creosote bush, coat their leaves in resins so thick and fragrant that the air around them smells like rain after a warm afternoon. Bees collect tree resins and transform them into propolis, the antimicrobial sealant they use to line the walls of their hives — a natural preservative that keeps the colony's honey stores from spoiling for months.

The antimicrobial agents the scientists used include thyme oil and citric acid, both of which are naturally derived — thyme oil being the same compound that gives Mediterranean herbs their heady, protective fragrance — 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%.1 This was likely due to bacteria being unable to infiltrate the coating, thus reducing the rate of natural decay — just as an insect's waxy epicuticle prevents fungal spores from germinating on its body.

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."4

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."1

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 — and nature's own packaging strategies may hold the most elegant answers.

Chang, Huibin, et. al. "High-throughput coating with biodegradable antimicrobial pullulan fibres extends shelf life and reduces weight loss in an avocado model." Nature Food, vol. 3, June 2022, pp. 428-436, DOI:10.1038/s43016-022-00523-w

Lindwall, Courtney. "Single-Use Plastics 101." National Resources Defense Council.

"Agency Response Letter GRAS Notice No. GRN 000645." U.S. Food & Drug Administration.

Jones, Sam. "Spray-On, Rinse-Off Food 'Wrapper' Can Cut Plastic Packaging." Scientific American.

MacPherson, Kitta. "Rutgers Scientist Develops Antimicrobial, Plant-Based Food Wrap Designed to Replace Plastic." Rutgers Today.

Jones, Sam. "Spray-On, Rinse-Off Food ‘Wrapper’ Can Cut Plastic Packaging."Scientific American.

MacPherson, Kitta. "Rutgers Scientist Develops Antimicrobial, Plant-Based Food Wrap Designed to Replace Plastic."Rutgers Today.