Have you ever put fruit in a paper bag to let it get a bit more ripe? Or been told to place an apple or a banana with an avocado to make it ripen faster? These are not “old wives tales” but rather tried and true ripening tricks caused by ethylene gas.
Science lesson of the day: Ethylene is a gas that naturally occurs when fruit is ripening or when a plant is injured or dying. It is used by the plants while fruit is still growing and maturing as well as once it has been picked and is waiting to be eaten. Some commercial farms use the ripening quality of ethylene gas to their advantage. They can harvest under-ripe fruit, such as bananas, which are firmer and easier to transport. Once the fruit has been packed and shipped to its final destination, such as a grocery store, it is then sprayed with ethylene gas to induce ripening. This method is widely used on grocery store tomatoes as well, which are picked green and will quickly turn red when sprayed. Ethylene gas does not, however, make up the flavors and aromas that come from field ripening of tomatoes. Basically all of the things that make tomatoes taste like tomatoes come along if they get ripe at the farm before they're picked (which is why grocery store tomatoes, although pretty, taste like not much of anything at all).
Some fruits like apples and bananas naturally produce and release more ethylene gas than others, and that can be used to our advantage at home - like helping soften up too-firm avocados or European pears. On the other hand, ethylene emitters can also be detrimental if placed with certain fruits and vegetables while in storage. For this reason, we have separate coolers for our apples and Asian pears that we pick at NSO, since the apples will make the pears ripen too quickly.
This is also a good reason to keep fruits and vegetables in different drawers or “crispers” in your own refrigerator. While the drawers are usually designed to allow for different humidity settings (high humidity to keep vegetables crisp and low humidity to keep fruit fresh), they also allow you to keep ethylene emitters from interfering with your other food. Here's a list of ethylene producing and ethylene sensitive produce.
So if you want to keep strawberries from going bad too quickly or stop carrots from becoming bitter, keep them away from apples in your refrigerator, either by judicious use of the crisper drawers, or by storing your apples in a plastic bag or container in the fridge.
As for the paper bag trick? Well, if you MUST purchase grocery store peaches or pears, sticking them in a paper bag (with or without an apple as well) will likely help them to soften up. But for your fruit from NSO, no bag is needed! Our peaches will soften up just beautifully on the counter in 2-3 days on their own, since we pick them ripe, but firm (learn more here). And they'll look a heck of a lot prettier that way than having a bunch of paper bags sitting around your kitchen!