Bananas tend to turn brown and ripen very fast. However, they can be preserved in different ways and the ripening process can be controlled. One way to preserve bananas is to separate them rather than leaving them as a bunch. The second way is to leave them in a polyurethane bag so that it does not react with the air which can lead to browning of the bananas. The third option is to store them in the refrigerator. Even if the skin of the bananas turns brown, the inside would not ripen as fast. Always keep the bananas separated from the vegetables, because the gases emitted from the vegetables can brown them faster. Incase the bananas ripen before they can be preserved, do not throw them out. Delicious dishes can be churned out with them. Try some of the recipes listed here - http://www.ifood.tv/network/ripe_banana_recipes/recipes