Food waste. Ethylene gas accelerates the ripening of fruits and vegetables and is responsible for millions of tons of food being lost each year during transport and storage. Now, researchers from the University of Copenhagen, among others, have succeeded in making clay capture this gas, and they hope this material will help reduce food waste over the long term. The study’s findings were published in the journal Applied Surface Science Advances.
Much of the fruit and vegetables we eat travel across the world before reaching store shelves in our homes. Yet millions of tons are lost annually before they make that journey.
A key reason is ethylene, a natural gas produced by many fruits and vegetables that governs their ripening. When produce is packed in sealed containers or packaging during transportation and storage, the concentration of ethylene in the air rises, speeding up the ripening process. As a result, a large portion of the shipment spoils before it reaches its final destination.
New research from the University of Copenhagen shows that ordinary clay could likely become part of the solution.
Ethylene is a natural plant gas emitted by many fruits and vegetables that regulates their ripening.
The buildup of ethylene during transit and storage can significantly shorten the shelf life of produce.
In the study, scientists used the clay mineral montmorillonite, which is widespread, non-toxic, and naturally occurring.
To examine how the gas moves through the clay material, the researchers employed advanced measurement techniques using neutrons and X-rays, along with thermal analysis, where the material is heated and the response pattern is measured.
The study demonstrates that chemically modified clay can both increase absorption and hold onto ethylene.
“Clay is an intriguing material because it’s natural, cheap, non-toxic, and found everywhere, plus our bodies can safely process it. We wondered: could we use chemistry and physics to modify clay so it traps the gas and thus slows down the ripening process? We succeeded,” says lead researcher Heloisa Bordallo from the Niels Bohr Institute.
Initially, the researchers tried to capture the gas using clay in its natural state. In this case, only a small amount was captured. By enlarging the voids in the clay’s structure through a gentle chemical treatment, the researchers created space to trap more gas without it being released again, while keeping the material non-toxic.
No previous research had managed to get clay to absorb such a large amount of ethylene, so they believe this concept has potential for use in food packaging.
“We now understand the fundamental physical and chemical processes that affect clay’s ability to absorb and hold ethylene. We didn’t know this before. So now we can control and optimize this process, which is necessary for its industrial application,” says study co-author Karina Kovalchuk, a member of Bordallo’s group at the Lawrence Berkeley National Laboratory.
According to the researchers, the study’s results serve as a kind of blueprint for designing environmentally friendly materials for food packaging that tackle the ethylene problem.
“We envision small sachets or pads made from powdered clay that can be placed with fruits and vegetables during transport to absorb ethylene—similar to the moisture-absorbing silica gel packets often found in packaging for items like shoes and electronics,” says Karina Kovalchuk.
Currently, the research team is working to optimize the chemical process to find the ideal balance between efficiency and environmental friendliness. They are also exploring ways to increase the clay’s ability to absorb ethylene and hold it for longer periods. Next, the clay material will be tested in food packaging, and hopefully, after that, the concept can move to the market.
The new material not only has the potential to cut food waste. Another consequence of the ethylene problem and long-distance shipping is that fruit often fails to develop its full flavor. Many fruits are picked early specifically to prevent them from spoiling in transit. But this means many processes within the fruit are not fully developed and cannot be “restored” later, even if the fruit ripens with ethylene during transport. And this affects taste and aroma.
“If we can solve the ethylene issue, it will serve two good purposes. First, we can reduce the global problem of food waste. At the same time, it will allow fruit to be harvested at later stages of ripeness, so consumers get fruit with the flavor they expect,” concludes Heloisa Bordallo.
Although the research focuses on ethylene and food, the scientists note that the findings could also have implications for other technologies where capturing specific gases with suitable materials is needed.
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