Shrimp shells could delay the ripening of bananas. (Photo: Stock File)
Crustacean shells used to lengthen shelf life of bananas
Monday, August 27, 2012, 14:10 (GMT + 9)
Scientists have figured out how to use chitosan -- a substance derived from shrimp and crab shells -- to delay the ripening of bananas for up to two weeks. Scientists speaking in Philadelphia at the 244th National Meeting & Exposition of the American Chemical Society described experiments designed to develop a spray-on coating that consumers could use themselves.
The coating, a "hydrogel," is a superabsorbent material made from chitosan. Xihong Li, PhD, who presented the report, noted that chitosan is a great option for the feat because of its action in killing bacteria that cause produce to rot.
"We found that by spraying green bananas with a chitosan aerogel, we can keep bananas fresh for up to 12 days," said Li, the study's leader, with Tianjin University of Science and Technology, Tianjin, China, Science Daily reports.
"Once bananas begin to mature, they quickly become yellow and soft, and then they rot. We have developed a way to keep bananas green for a longer time and inhibit the rapid ripening that occurs. Such a coating could be used at home by consumers, in supermarkets or during shipment of bananas," Li continued.
Li explained that bananas, like other fresh fruit and vegetables, are alive and actually "breathing" even after picking, releasing carbon dioxide through their skin. The more a banana breathes, the quicker it ripens.
Unlike with many other fruit, bananas’ respiration rate does not slow down and bananas do not ripen slowly. The banana's pulp discharges a chemical that increases respiration and the pulp turns into the sugars that give bananas its sweet flavour.
As respiration continues, the process speeds up and bananas become exceedingly sweet and mushy. That is when bacteria on the skin start to thrive and cause the banana to rot.
In the study, Li's team showed that the chitosan hydrogel coating put the brakes on the bananas’ respiration and killed bacteria that cause rotting, keeping the fruit fresh for almost two weeks.
Li's team is now working on a new ingredient for producing the hydrogel that would replace an existing ingredient that cannot be used commercially.
This study was supported by a National Natural Science Foundation of China Grant and the China Postdoctoral Science Foundation.
By Natalia Real