A lot of fruits start to turn colors once they've been cut due to an enzyme called polyphenol oxidase that turns the fruit colors when it's exposed to oxygen. You can prevent this reaction in apples with a honey-water bath, but what about avocados?
Many claim that leaving the pit in the cut half of the avocado keeps it fresh for longer, which is why some avocado storage devices have a place for the pit, but I've never had any luck with this method. Others say to squirt fresh lemon or lime juice onto the exposed surface, but that can make it slimy.
Some people swear by rubbing a very thin coat of oil onto the cut surface, then wrapping the avocado tightly in plastic wrap. Much like cheese, this creates a kind of seal from the air. Olive oil is the most common suggestion, but you could go one step further and use avocado oil to keep that avocado-y flavor, if you have it on hand.
However, The Kitchn's Dana Velden has found that the best way to keep an avocado from turning brown after it's been cut is to store it with an onion.
It works because onions contain sulfur, which prevents the enzyme from interacting with the air. Just put the cut avocado in an airtight container with a piece of onion, cover with a lid and store in the refrigerator. It should keep for a couple of days.
This is the same exact method that CHOW recommends, but they prefer to use red onions, chopped at the bottom of the container instead.
Dana says a layer of diced onions on top of guacamole works the same way, though I just cover it with water instead.
How do you store cut avocados? Got any more tips for keeping them fresh longer? Share with us in the comments.