Most of us have had the unfortunate experience of discovering some leaky, moulding fruit at the bottom of a plastic carton. Now, researchers may have a solution: a flexible nanofiber mat, infused with antioxidants isolated from red wine, could help tackle this inconvenience—along with the enormous challenge of global food waste.
Several million tons of food are wasted around the world every year, partly due to spoilage. One of the biggest culprits behind that spoilage is oxidation, a natural process that occurs when air that comes into contact with food and sets off a chain of molecular reactions, triggering the release of new compounds—which is what makes food turn brown, go soft, emit unpleasant odors and generally become unpalatable.
But, antioxidants can slow down this process by stabilizing molecules, and in the case of produce, keep it fresh for much longer. The challenge is finding a way to provide a sustained source of antioxidants to treat food. Writing in the journal ACS Applied Materials and Interfaces, the researchers, from Texas A & M University, explain how their mat—bristling with antioxidant-infused fibers—might provide a solution.
To craft the mat, they first had to find a suitable antioxidant. For this, they settled on tannic acid, a molecule that happens to be abundant in red wine, and is known to be antioxidant-rich, thanks to compounds within it called polyphenols. An added bonus of tannic acid is that it contains antibacterial and antiviral properties, too.
The researchers then mixed the tannic acid with polymers, to create the substrate that would go on to form the mat. To transform this into a fibrous material, they used a technique called ‘electrospinning’. This process relies on the use of an electrical charge to draw out microscopically-fine threads, with nanoscale diameters, from a syringe. Using those fibers, the researchers were then able to weave them into a cloth-like mat.
The researchers invented the mats with a diversity of biomedical and environmental applications in mind. But the food industry is one clear potential beneficiary, says Svetlana Sukhishvili, lead author on the study, and professor of materials science and engineering at Texas A & M University. “Oxidation is an essential part of food spoilage, thus coating or packaging materials which slow down oxidation are promising for protecting food,” she says.
The researchers haven’t yet tested the mats out on food, Sukhishvili explains. But she thinks there are several ways the versatile product could be used to keep food fresh. “At this point of the technology’s development, we envision application at the smaller scales, such as for wrapping or lining paper for fruit and veg trays.”
This isn’t the first time scientists have developed antioxidant mats. But typically, they’ve been made into thin, flat, one-dimensional sheets. The benefit of this new invention is that the use of nanoscale fibers dramatically increases the surface area, and thus boosts exposure to the antioxidants.
What’s more, the researchers discovered that their mats could go on emitting tannic acids and their associated antioxidants into the surroundings for up to 20 days. This large window of protection could be a game-changer for keeping produce fresh throughout the supply chain, and in grocery stores—and potentially even in consumers’ homes.
In making the mat, the researchers also selected a polymer called polyvinylpyrrolidone, which is able to use hydrogen to bond especially well with tannic acid. This made the mats 10 times stronger than others that have come before it, which also means they could more reliably fulfill their antioxidant role. Plus, “importantly, the components of our fiber mats are ‘edible’, or considered as generally regarded as safe for food consumption,” Sukhishvili added.
With further refinement—which is the researchers’ next goal—this fibrous mat might one day bring an end to soggy-bottomed fruit—and become a valuable tool for fighting food waste.
