Continuing efforts to improve the preservation of food have focused on packaging. Ideally, packaging would prevent bacterial contamination and permeability to both oxygen and water vapor. Control of ethylene buildup around foods is also crucial, as an excess of the gas trapped underneath packaging causes over-ripening and rot.

Control tomatoes (left) rotted after six days while those wrapped in a new clay-based film (right) stayed fresh. Source: Hayriye ÜnalActive food packaging materials developed by researchers at Sabanci University (Istanbul, Turkey) fulfill these food preservation requirements. The team engineered a composite of polyethylene incorporating clay halloysite nanotubes to scavenge for ethylene and provide a gas barrier. The nanotubes prevent oxygen from entering the film, and prevent water vapor and other gases from escaping. The material also absorbs ethylene to keep it from accumulating.

A natural antibacterial essential oil found in thyme and oregano called carvacrol was loaded into the nanotubes, which in turn were applied to the inner surface of the packaging film to kill microbes.

Testing entailed wrapping tomatoes, bananas and chicken in the film to test its effectiveness over varying amounts of time compared to foods wrapped in plain polyethylene. After 10 days, tomatoes wrapped with the new film were better preserved than the control vegetables. The new film helped bananas stay more firm and keep their vibrant yellow color after six days compared to the control fruit. And chicken enveloped with the experimental film and refrigerated for 24 hours showed significantly less bacterial growth than chicken in plain polyethylene.

Future research will test the new film to make sure it is safe and nontoxic.

The research will be presented at the 254th American Chemical Society National Meeting & Exposition, August 20-24, 2017, in Washington, D.C.