Chinese researchers developing spray to extend banana shelf life
Chinese researchers have discovered a substance found in crab and shrimp shells can be used to delay banana ripening, applied as a spray that slows the fruit's respiration and kills bacteria. 
The substance 'chitosan' is already used in many biopesticide solutions in horticulture, but researchers from the Tianjin University of Science and Technology project claim this is the first time it has been applied to bananas.
Dr Xihong Li heads up the research and presented the findings at the National Meeting & Exposition of the American Chemical Society in Philadelphia this week.
He said chitosan was attracting considerable attention in efforts to keep fruits and vegetables fresher for longer due to its low cost, ability to kill bacteria that lead to rot, and other properties.
"We found that by spraying green bananas with a chitosan aerogel, we can keep bananas fresh for up to 12 days," Li said.
"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 explained that the more a banana respires, the quicker it ripens, and unlike other fruits the banana's respiration does not slow down.
The banana's pulp releases a chemical that boosts respiration, and the pulp converts into the sugars that produce that sweet, banana taste. As respiration continues, however, the process speeds up, and bananas become unpleasantly sweet and mushy.
Li said the study showed the chitosan hydrogel coating slowed down respiration and killed bacteria that cause rotting, keeping bananas fresh for almost two weeks.
However, the hydrogel is not yet ready for use as the team are looking for a new ingredient to replace an exiting one in the product that cannot be used commercially.
Bananas are the world's most popular sweet fruit (tomatoes have the largest production) with 102 million metric tons (224 billion pounds) produced each year around the globe, according to Food and Agriculture Organization (FAO) data.
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