In This Article
In ancient Egypt, farmers would take a batch of unripe figs and slash open a few of them to get them to ripen sooner. In China, it was common practice to burn incense in a storage room of unripe pears to get them to ripen.
Perhaps you remember your grandmother putting ripe bananas in a brown bag with unripe avocados to get them to ripen by dinner time. Or, maybe your mother would remind you to hang your bananas away from the other fruits. In the twentieth century, farmers would burn kerosene to heat the sheds in order to ripen citrus fruits in Florida – but was it the heat that incited the ripening?
The Secret Fruit Ripening Ingredient
Way back in 1924, Frank Denny, a scientist from the Department of Agriculture, discovered that smoke from kerosene contains small amounts of a molecule called ethylene and that treating fruits with a small amount of ethylene gas would encourage them to ripen. He found out that all fruit ripens faster when exposed to even the smallest amount of ethylene gas.
It turns out that Chinese incense had minute amounts of ethylene gas and was known as an accelerator for ripening fruits.
Further experiments showed that the air around ripening fruits is rich in, you guessed it, ethylene gas. As it turns out, all fruits emit ethylene gas when they start to ripen. One whiff of ethylene gas on an apple tree and the whole tree of fruits starts to ripen. In fact, ethylene gas acts as a hormone for fruits, letting them know when to ripen. The release of ethylene gas is determined by the season, environmental stressors, drought and other factors.
Ripening is Contagious
Once one fruit releases ethylene gas, the entire bunch jumps on the ripening wagon, and soon the whole tree is an ethylene smoke signal. Animals that love fruits are able to detect the ethylene gas for miles and track down the ripe fruit. By making sure all the fruits ripen at the same time, the tree ensures that all the fruits are eaten at one time as well. In this way, all the seeds are carried about and dispersed, allowing for the growth of new fruit trees.
So, grandma had it right! Want to eat those avocados soon? Put them in a bag with some soft bananas and wait a couple of hours.
Enjoy in good health!
- Chamovitz D. What A Plant Knows. Scientific American Press. New York. 2012 p29-31.