Onions have layers and layers of skin, so it seems like they never go bad, but they do. Even if stored under the best conditions, they will start to get icky after two or three months. Onions that are stored near potatoes will spoil even faster. The chemicals that both onions and potatoes emit react in a way that causes both vegetables to spoil, so be sure to separate the two. You’ll be able to tell when onions are spoiled by the way the smell, look, and feel.
Look at the onions. Fresh onions look clean and firm. The onion should not be sprouting or have dark spots or signs of decay. Avoid onions that look like they have any moisture on the neck.
Feel the onions. Onions should be firm and smooth to the touch. Any onions that have soft spots or feel less than firm should be trashed.
Smell the onions. Decaying onions will give off distinct foul odor and should be thrown out.
- Store green onions in the refrigerator and use within two weeks.
- Store dry onions (yellow, white, red) in a basket in a dark, cool area with plenty of air.