The research was led by Bordallo’s group at the University of Copenhagen in collaboration with her group members, Karina Kovalchuk and Leander Michels at Lawrence Berkeley National Laboratory.
Photo Credit: Lawrence Berkeley National Laboratory
Scientific Frontline: Extended "At a Glance" Summary: Ethylene-Absorbing Montmorillonite Clay
The Core Concept: Researchers have engineered a chemically modified form of the naturally occurring clay mineral Montmorillonite that absorbs and retains large quantities of ethylene gas (\(\text{C}_2\text{H}_4\)), effectively delaying the ripening and degradation of agricultural produce.
Key Distinction/Mechanism: While untreated clay captures minimal gas, this modified variant undergoes a mild chemical treatment to expand its structural voids. This physical chemistry approach allows the non-toxic material to trap significantly higher volumes of the ripening hormone without releasing it back into the immediate environment.
Major Frameworks/Components:
- Montmorillonite: A widespread, inherently non-toxic smectite clay mineral utilized as the highly porous base structure.
- Ethylene (\(\text{C}_2\text{H}_4\)): A gaseous plant hormone responsible for accelerating the ripening and eventual senescence of climacteric fruits and vegetables.
- Void Expansion: The application of targeted chemical treatments to increase the internal surface area and porosity of the clay lattice.
- Advanced Metrology: The use of neutron scattering, X-ray characterization, and thermal analysis to quantify and observe gas kinetics within the clay matrix.
Branch of Science: Materials Science, Physical Chemistry, and Agricultural Science.
Future Application: The integration of ethylene-absorbing clay powders into small, permeable packets or pads—similar to silica gel desiccants—placed inside commercial food packaging and shipping containers.
Why It Matters: Controlling ethylene accumulation offers a dual benefit: it promises to drastically reduce the millions of tons of global food waste generated during transit, while also allowing producers to harvest crops later in their growth cycle to ensure optimal flavor development.
The gas ethylene causes fruits and vegetables to ripen faster and is responsible for millions of tons of food being lost annually during transport and storage. Now, researchers from the University of Copenhagen, among others, have succeeded in modifying clay to collect the gas and hope that the material can help reduce food waste in the long term.
Avocados from Chile, bananas from Costa Rica, tomatoes from southern Spain, and mangoes from Brazil—many of the fruits and vegetables we eat have traveled across the globe before reaching store shelves at home. However, millions of tons are lost every year before they make it that far.
One of the main reasons is ethylene—a natural gas that many fruits and vegetables produce and that controls their ripening. When fruits and vegetables are confined in closed packaging or containers during transport and storage, the concentration of ethylene in the air increases, accelerating the ripening process. As a result, a large portion of the cargo ends up rotting before it reaches its final destination.
Clay May Be the Solution
New research led by the University of Copenhagen shows that ordinary clay could be part of the solution.
"Clay is an interesting material because it is natural, cheap, nontoxic, and found everywhere—and we can absorb it safely into the body. Our thought was: Can we use chemistry and physics to modify clay so that it captures the gas and thus slows down the ripening process? We have succeeded in doing so," says Associate Professor Heloisa Bordallo from the Niels Bohr Institute, who led the new study.
First, the researchers tried to capture the gas with clay in its natural form, which captured only a small amount. By increasing the voids in the clay's structure with a mild chemical treatment, the researchers made room for the clay to capture more gas—without allowing it to escape—while keeping the material nontoxic.
Researchers had never previously succeeded in modifying clay to absorb such large amounts of ethylene, which is why they believe the concept has potential for use in food packaging.
"Now we know the fundamental physics and chemistry of the process that affects the clay's ability to absorb and retain ethylene. We didn't know that before. So now we can control and optimize the process, which is necessary for it to be used in industry," says Karina Kovalchuk, a member of Bordallo’s group at the Lawrence Berkeley National Laboratory and first author of the study.
Degasser in Food Packaging
According to the researchers, the results provide a design manual for developing sustainable materials for food packaging that tackle the ethylene problem.
"We imagine small bags or pads of powdered clay that can be placed with fruits and vegetables during transport and absorb ethylene—in the same way as the moisture-absorbing silica bags that often come in the packaging when you buy, for example, shoes and electronics," says Kovalchuk.
The research group is currently working on optimizing the chemical process to strike the right balance between effectiveness and environmental friendliness. They are also investigating whether they can make the clay capture even more ethylene and retain it for even longer. Next, the clay material will be tested in food packaging, and hopefully, the concept can then be brought to market.
Two Good Purposes
The new material has the potential to do more than just reduce food waste. Another consequence of the ethylene problem and long transport times is that fruits often do not develop their full flavor. Much fruit is harvested early precisely to prevent it from rotting along the way. However, many biological processes in the fruit are thus not fully developed and cannot fully catch up later, even if the fruit ripens with ethylene during transport. This ultimately affects the taste and aroma.
"If we manage to solve the problem with ethylene, it serves two good purposes. First, we can reduce the global problem of food waste. At the same time, it can make it possible to harvest fruit later in the ripening process, so that consumers get fruit that tastes as it should," concludes Bordallo.
Although the study focuses on ethylene and food, the researchers point out that the results may also have implications for other technologies where materials need to collect certain gases.
Funding: The research is supported by the Laboratory Directed Research and Development (LDRD) Program of Lawrence Berkeley National Laboratory and the Carlsberg Foundation.
Published in journal: Applied Surface Science Advances
Authors: K. Kovalchuk, L. Michels, W.P. Gates, M.L. Martins, G.W. Greene, and H.N. Bordallo
Source/Credit: University of Copenhagen
Edited by: Scientific Frontline
Reference Number: ms062226_01