If freshly bought bananas are stored in a full fruit basket, they won't stay yellow very long. The reason for the rapid ripening is the chemical compound known as ethylene. The gaseous plant hormone not only functions as a messenger substance within an individual fruit, but also influences other specimens nearby.
Ethylene triggers a real chain reaction by stimulating the production of (more) ethylene in other plants and fruits. And more ethylene means faster ripening. Therefore, fruits like apples that emit particularly high levels of ethylene cause premature ripening in, say, banana, which shows a particularly strong reaction in response to the hormone. When storing this foodstuff together, rapid ripening can become an undesirable side effect. Fruit cannot be stored as long—which not only leads to losses of food at home in the fridge, but also in the entire supply chain from the importer to the wholesale and retail trade.
In short: To counteract the accelerated ripening process, ethylene must be kept away from fruits and vegetables. For this purpose, Empa/ETH Zurich researchers Huizhang Guo and Mirko Lukovic have developed an idea to degrade ethylene released by fruits and vegetables.
The concept is based on a delignified wood structure enriched with a catalyst that is dispersed at an atomic level. Wood consists of three basic substances: cellulose, hemicellulose and lignin. The researchers used a protocol developed in the Wood Materials Science professorship at ETH Zurich and Empa and with the help of an acid solution dissolved both lignin, wood's binding substance, and a part of the hemicelluloses.
This makes the remaining cellulose structure extremely porous with a very large specific surface area. These properties make the delignified wood a perfect natural scaffold for a catalyst.