Have you ever wondered why placing a bunch of bananas in a bag of unripe tomatoes can help them to ripen quickly? The secret chemical responsible for ripening of fruits is Ethylene, C2H4! Fruits such as apples, tomatoes, bananas release ethylene gas in the ripening process. The ethylene gas produced can cause surrounding fruits to ripen more quickly. Ethylene gas is sometimes sprayed onto fruits and vegetables to speed up the ripening process.
To maintain fruits freshness, ethylene can be removed via oxidation to ethylene glycol, CH2OHCH2OH (or even CO2). This is done industrially using potassium permanganate, KMnO4. However, there are simpler ways to keep your fruits stay fresher for a longer period of time. (1) Avoid placing ripe and unripe fruits such as bananas, oranges and apples together, (2) Using zeolite (volcanic mineral), a microporous natural material (commonly found in washing powder or even cat litter) that readily adsorbs gases and ions. Zeolite is commercially available (and cheap) and you can even DIY your own zeolite pouches to place around fruits that you would want to keep fresh for a longer period of time!