A common household tip is if you buy green, under-ripe lemons or bananas, you can make them ripen faster by keeping them in paper bags.
In the past, Chinese growers used to ripen fruit by keeping it in a room with burning incense. And in the Old West, farmers used to “cure” fruit with kerosene stoves. Those farmers thought it was the heat ripening the fruit.
But when people in modern times tried to replicate those techniques, they realized it wasn’t the heat at all. It was a gas.
Proverbs And Science
The gas involved in all of those processes is called ethylene. It can come form burning fuels like kerosene,but it’s also made naturally by all parts of a plant at one time or another.
Ethylene stimulates germination of the seed, flowering, ripening of fruit, dropping of fruit, dropping of leaves. Ethylene produced by ripe fruit will stimulate another nearby fruit to ripen.
So, there is a chemical basis for the proverb about one rotten apple spoiling the whole barrel.
Bananas, Roses, Tomatoes
Ethylene is used in commercial agriculture, to stimulate the ripening of bananas, tomatoes, and citrus fruits and to help give them the colors people expect; ethylene even makes roses drop their leaves.
Fruit shippers usually want to stop the ripening process, so they store fruit in rooms that have ethylene chemically removed from the air.
The next time you have fruit that you want to get riper, remember that ethylene can help.
Sources And Further Reading:
“Ethylene,” in McGraw-Hill Encyclopedia of Science and Technology, 6th ed. New York, 1987.
Salisbury, F. B., and C.W. Ross, Plant Physiology, 3rd ed. 1985
“Ethylene: The Ripening Hormone.” WSU Tree Fruit Research & Extension Center. October 29, 2010. Accessed June 21, 2017.