Here's How To Keep Avocados From Going Bad
Avocados are so good, but they can go bad so fast. They have an ideal window in which to eat them that seems to last approximately 45 minutes. However, there are some tricks to help keep avocados good a little bit longer.
Most people buy avocados that still need a few days to ripen, as it's very difficult to find any in the store that are in that sweet spot where they are ripe enough to eat, but not so soft they are starting to go bad. It's better to just buy some that need a little time to ripen. Now, how you store them depends on when you plan to eat them. If you are going to eat the avocado within a day or two, the counter is the best place to store them. This allows them to breathe and ripen (via Cooking Light).
However, if the avocados aren't ripe, which they usually aren't, place them directly into the fridge. Three days before you plan to eat it, place the avocado on the counter to ripen (via Mind Body Green).
Now you may have another problem. Depending on what you're using the avocado for, you may have some leftover that has now been cut. If you are eating half of the avocado, use the half without the pit first, as the pit will help preserve the other half. Take some lemon or lime juice and rub it on the visible green flesh of the avocado.
Preserving leftover avocado
This will prevent the avocado being exposed to oxygen, which is what causes the browning process. Next, wrap the avocado in plastic wrap that is covered as tightly against the green flesh as possible to further prevent any air getting through. This will give you an additional day or two to finish it.
Another trick that helps preserve a cut avocado is to store it in a reusable container and add a piece of onion before sealing the container shut. The sulfur in the onion can help prevent browning. Store the container in the refrigerator. This has the potential drawback of the avocado picking up a slight oniony flavor. Most likely, you won't notice it, though it's probably best not to use this method if you will be using the avocado in something sweet (via Today).
If you are worried about that onion taste, try brushing oil, such as olive oil (or even avocado oil if you have it) on the green fleshy part of the fruit. Then place the avocado in an airtight container and you will likely have an extra day or two to use the avocado.
Another method for storing avocado is to submerge it in water in a reusable container and store it in the fridge. This method is best if you will be using the avocado in something where you will smash it, such as guacamole.
Storing guacamole so it won't turn brown
The water method, though, doesn't work great for slices. You can turn the avocado upside down on a dish to drain as much excess water as you can a few minutes before using it, but that won't entirely get rid of the mushiness.
To store guacamole, you want to make sure you store it airtight. Cover the bowl or reusable storage container with plastic wrap. Don't just cover the container, though. Instead, take the plastic wrap and place it directly against the guacamole. You should be able to feel the texture of it and push out any air bubbles to prevent any exposure to air, and therefore oxygen, which will turn your guacamole brown. You should be able to store the guacamole in the fridge for a day or two. If any air does get in, you can scrape off the brown part and eat the rest of the guacamole.