Making food last for longer is something humans have been working on for millions of years, and we’re not out of ideas yet.
Since ancient times, food preservation has meant that more people get fed, over a wider span of time, and helped protect against food scarcity. In the more modern era, it also means being able to try foods from far-flung places – and outside of season.
Researchers led by a team from Kyushu University in Japan, publishing their work in Food Research International, have now come up with an innovative new method of food preservation that’s natural and straightforward. It could cut down on packaging waste as well as food waste.
It’s based on a nanomaterial with one key ingredient: leftover pumpkin peel.
“Our lab has long focused on extending the shelf life of agricultural produce while reducing reliance on petroleum-based plastics,” says food scientist Fumihiko Tanaka from Kyushu University.
The peel was prepared for its alternative use by being heated under high pressure, after which it was freeze-dried to break it into carbon quantum dots (CQDs), very tiny black powder particles previously shown to have useful properties for food packaging.
After being combined with plant fibers and gelatin, the new peel-based material was tested against conventional plastic packaging and no packaging at all, with cherry tomatoes used as the test foodstuff.
Analyzing the tomatoes after 20 days, the researchers found the pumpkin peel material outperformed having no packaging at all, and beat standard plastic on blocking ultraviolet (UV) light, curbing microbial growth, and preserving antioxidant activity – though conventional plastic still did better on limiting moisture loss.
The material based on these little carbon dots is well within thresholds for toxicity too, the researchers point out.
“We understand safety is a key concern,” says food scientist M.A. Reshaka Kavindi from Kyushu University.
“Cell viability tests confirmed the material is non-toxic below 2 mg/mL, and the coating itself uses only a fraction of that amount, at roughly 0.01 millimeters thick. Consumers can further reduce exposure simply by washing or peeling.”
The benefits keep on coming. The nanomaterial can be sprayed on as well as used in actual packaging, which is useful for protecting specific spots on fruit and vegetables – and further reducing waste.
Given that the peel accounts for around 10–12 percent of the total mass of a pumpkin but is usually tossed aside (even though it is edible), it’s a neat way of doing something useful with food waste.
“Conventional antimicrobial packaging typically relies on metal nanoparticles like zinc oxide or silver, which carry a larger environmental footprint than CQDs,” says food scientist Fumina Tanaka from Kyushu University.
“Ours are derived from organic matter and show good biocompatibility at effective concentrations, something critical for any food contact material.”
Food waste is a significant issue. It’s estimated that around 40-50 percent of harvested fruits and vegetables never reach consumers.
The peel packaging isn’t ready to be rolled out to stores yet, though – it’s only been tested with one food, in limited conditions for 20 days – but it’s a promising start.
Looking ahead, the team hopes to incorporate more natural agents into the packaging film, to further protect the food it’s wrapped around (against aggressive mold, for example). There’s also work to do in scaling up this idea.
There’s a nice added bonus – CQDs glow under UV light as well, which is something the researchers might be able to find a use for, too.
Related: Scientists Discovered An Amazing Practical Use For World’s Leftover Coffee Grounds
“Beyond the environmental benefits, I’d also love for this material to bring a bit of fun to food packaging,” says Fumina Tanaka.
“Under UV light, the carbon dots fluoresce, and the color shifts with particle size. If we could eventually find a way to render text or illustrations with it, that would be pretty exciting too.”
The research has been published in Food Research International.
This article was fact-checked by Rebecca Dyer and edited by Peter Dockrill. While we pride ourselves on our process, we are only human. If you spot a mistake, please let us know.
