Clay-based antimicrobial packaging keeps food fresh for longer

Scientists have developed a new packaging film with clay nanotubes and antibacterial essential oils that can prevent microbial growth and over-ripening of fruits, keeping them fresh for longer.
People around the world have been trying to preserve fruits, vegetables and meats since ancient times. From the traditional methods of salting or fermenting to the more modern methods of canning, freezing or wrapping in plastic films, food preservation has always been important.
"Food packaging that is capable of interacting with food can contribute to safety and prevent economic losses from spoilage," said Hayriye Unal, from Sabanci University in Turkey.
"Specialised films that can preserve a wide array of foods are highly sought after," said Unal.

According to the US Department of Agriculture, about 30 to 40 per cent of the food that farmers produce in the country goes to waste, researchers said.
Over the past two decades, scientists have been developing alternative ways to preserve food, with an extensive focus on packaging.

"While companies can already make many films that prevent fruit and vegetables from drying out, incorporating additional properties in the same film is a challenge," said Unal.
Bacterial contamination and permeability to both oxygen and water vapour are major issues that scientists are addressing. Another challenge is 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.
However, an excess of ethylene trapped underneath the packaging film can cause food to over ripen and rot.
To meet the demand for multi-functional packaging, Unal started with a polyethylene film. To scavenge for ethylene and provide a gas barrier the group incorporated clay "halloysite nanotubes," which are small, hollow cylinders.
The nanotubes prevent oxygen from entering the film, and prevent water vapour and other gases from escaping. In addition they keep ethylene from building up by absorbing it.
The researchers loaded these nanotubes with a natural antibacterial essential oil found in thyme and oregano called carvacrol and coated the inner surface of the packaging film with the loaded nanotubes to kill microbes.

The team wrapped 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.
In addition, the new film helped bananas stay more firm and keep their vibrant yellow colour after six days compared to the control fruit.
The chicken enveloped with the experimental film and refrigerated for 24 hours showed significantly less bacterial growth than chicken in plain polyethylene.