Clay packaging could help preserve produce

New research shows that clay-based antimicrobial packaging keeps food fresh.

Control tomatoes (left) rotted after six days, while those wrapped in a new clay-based film (right) stayed fresh.
Source: Hayriye Ünal, PhD., Sabanci University, American Chemical Society.

It turns out the answer to rotting fruits and vegetables could be clay.

Scientists have developed a packaging film coated with clay nanotubes packed with an antibacterial essential oil that provides a one-two punch—preventing both over-ripening and microbial growth. The hope is the new film could help improve the shelf life of perishables.

Hayriye Ünal, PhD., Sabanci University, discussed the research during a recent press conference at the American Chemical Society’s 254th National Meeting in Washington, DC.

“The bananas packaged with our film retained their color and were free of brown spots, whereas the control bananas had a darker color and were full of brown spots,” she says. “And strawberries that we packaged with our films demonstrated almost 50 percent less weight loss compared to strawberries packaged with [plain] polyethylene films.”

The team also wrapped tomatoes in the film and compared them to food wrapped in plain polyethylene. After 10 days, the tomatoes wrapped with the new film were better preserved than the control vegetables.

Produce wasn’t the only test food though. The researchers also wanted to see how the film would work on chicken, and the results were encouraging. Chicken enveloped with the experimental film and refrigerated for 24 hours showed significantly less bacterial growth than chicken in plain polyethylene.

Specifically, the film was created to address the issues of bacterial contamination and permeability to both oxygen and water vapor. It also was designed to prevent too much ethylene from building up around foods. Ethylene is a compound naturally released by fruits and vegetables that aids in the ripening process, but an excessive amount trapped underneath the packaging film can cause food to over ripen and rot.

In an effort to scavenge for ethylene and provide a gas barrier, the group incorporated clay “halloysite nanotubes,” which are small, hollow cylinders, into its film. The nanotubes prevent oxygen from entering the film and prevent water vapor and other gasses from escaping. They also keep ethylene from building up by absorbing it.

The researchers loaded these nanotubes with a natural antibacterial essential oil, called carvacrol, found in thyme and oregano and coated the inner surface of the packaging film with the loaded nanotubes to kill microbes.

Ünal says they are working with packaging companies on bringing the film to market.

“I believe the food packaging materials we prepared by using only natural elements have a lot of potential for keeping food fresh and safe,” she says. “[The fact that] all the components are natural makes it very unique, because we have clay, [and] we have thyme oil and polyethylene. So, there’s not much concern about toxicity.”

However, she did say the team did not test the taste of the food they wrapped in the film and that would have to be studied before it was brought to market.

For more information:
The American Chemical Society, www.acs.org.

Looking for a reprint of this article?
From high-res PDFs to custom plaques, order your copy today!

Crystal Lindell has more than 10 years of journalism experience, and worked primarily at daily newspapers before joining BNP Media 2010. Before joining Food Engineering as the Managing Editor, she was the managing editor of a sister publication, Candy Industry Magazine, where she learned first-hand the joys of eating chocolate for breakfast. Lindell holds a master’s degree in public affairs reporting from the University of Illinois – Springfield and a bachelor’s degree in political science from Western Illinois University.