Avocados are tricky things. They make you wait until they decide to ripen, then quickly speed past the sweet spot into mushy, sad goo. They're also not cheap. So when the avos are in, you really want to squeeze the most value out of them by storing them right. For the longer term, there are just a couple methods to preserve them.
For the most part, avocados do not ripen on the tree. This is good news in that they are able to be shipped in their durable, unripe state.
It's best to plan ahead and buy avocados a day or two in advance of when you plan to use them, so they have time to ripen properly.
Most importantly, do not refrigerate your avocados, at least not initially. Once picked from the tree, avocados, much like bananas, produce ethylene, which triggers the ripening process. The optimal temperature for this is 68°F/20°C. Fresh-picked avocados should ripen under these conditions within three to six days. When ripe, the avocado should yield gently to pressure, but not be squishy.
If you want to accelerate the ripening process, place the avocados in a paper bag. This concentrates the ethylene gas. If you add other fruits, such as bananas and apples, they will all ripen more quickly together.
Once an avocado is ripe, you can hold it in that state longer by placing it in the refrigerator. While this will not halt the ripening process altogether, it will retard it greatly.
Similarly, if you have a lot of avocados and want them to ripen at different times, you can keep them in the refrigerator until a couple days before you want them to ripen.
Cut avocados oxidize quickly and turn brown. While this does not impact the edibility of the fruit, it is aesthetically unpleasant.
To save a cut avocado, brush the exposed flesh with lemon juice, cover with cling wrap, and refrigerate. The acidity of the lemon juice helps stop oxidation, as does limiting the amount of oxygen that comes into contact with the flesh.
For long-term storage, freezing is the only effective method. The National Center for Home Food Preservation (NCHFP) recommends mashing the ripe avocados into a purée to freeze; whole or sliced avocados do not freeze well. For best results, add a tablespoon of lemon juice to every two avocados to preserve color.
Another method of extending avocados' life span is in the form of a quick pickle. Cubed avocado can be pickled in a simple vinegar brine, or feel free to add some spices to the mix. The pickled avocado will keep in the refrigerator, so long as it stays submerged, up to two weeks. The color will fade over time. This pickle is not recommended for canning.