Wednesday, August 22, 2012

New product can keep fruit fresh for two weeks

A spray that stops bananas from rapidly turning to mush is being developed by scientists.
When used to coat green bananas, it slowed their ripening and so kept them fresh for almost a fortnight.
By contrast, supermarket-bought bananas often go brown and soggy within two or three days.

It is believed that the spray could help save some of the 1.6million bananas thrown away in Britain every day.
Dr Xihong Li, who made the spray from chitosan, a substance derived from shrimp and crab shells, said: ‘We found that by spraying green bananas with a chitosan aerogel, we can keep bananas fresh for up to 12 days.
‘Once bananas begin to mature, they quickly become yellow and soft, and then they rot.
‘We have developed ways 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.’

The spray, which is being developed at Tianjin University of Science and Technology in China, is clear and tasteless and said to be completely safe.
It works by killing bacteria and slowing down the rate at which the fruit breathes.

Bananas breathe by taking in oxygen and giving off carbon dioxide but do it through their skin.
The faster they breathe, the quicker they ripen, until they start to become soggy.
Bacteria on the skin then thrive and the banana rots.
But an American Chemical Society conference heard the recipe has to be refined to make it suitable for commercial use.
Bananas are usually transported while still green and ripened in warm humid conditions similar to those they have experienced naturally.
The gas ethylene is used to start the ripening process.
Bananas also produce ethylene as they ripen, which is why they rot faster when kept in a bag, as the gas builds up.


The coating is a so-called hydrogel, a type of superabsorbent material with many medical and commercial uses. 
It is made from chitosan, derived from shellfish.
Scientists sprayed the covering all over the fruit, which blocks the bananas' respiration. 
The covering also kills bacteria on the bananas' skin that otherwise promotes rotting.
The covered fruit stayed fresh for 12 days, while non-sprayed fruit rotted much more quickly.
The scientists hope it could be available commercially to growers, supermarkets and consumers to use at home.
By Mail Online

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