Avocados, once fully ripe, can turn to mush overnight. Avocados are picked and loaded in various state of ripeness before sending the fruit to your store. When purchasing avocados at the store, the key is to pick a variety from not quite ripe to fully ripe. Ripeness can be determined by how soft the avocado is when the skin is pressed. The softer the avocado, the more fully mature and ripe the fruit is.
Feel the flesh of the avocado immediately upon purchase or picking. This will determine how ripe the fruit is. Firm fruit is still immature. In general, the darker the color the more ripe the avocado. Bright green is a sign of immaturity, while dark green or brown is a fully ripe fruit.
Store soft avocados in a brown paper bag in the refrigerator and use as soon as possible. If a paper bag isn't available, use a plastic storage bag, but do not seal it shut. In most cases, a soft avocado should be eaten within two days after refrigeration. Longer storage will turn the green flesh to an unattractive brown, which will have an off-taste.
Allow unripe avocados to sit on a counter until the flesh becomes soft. Once soft, store in the refrigerator.
Make guacamole from ripe avocados to extend the life of the fruit.
Dip avocado slices in lemon or lime juice to prevent browning of the cut fruit.