Bad onions are obvious. Onions that are mushy should be discarded without a second thought. The same holds true for pungent onions and onions with high moisture.
Small brown spots, moist spots, or a softer feel are some of the less evident indications that may be present.
An onion is safe to use if it is possible to remove these spots from a portion of the onion without affecting any other parts of the onion.
A sprouting onion with no other evidence of deterioration is the same. Remove any sprouts or shoots you don't want to eat by slicing up the onion in half, and you'll be good to go.
However, if you see mold or have any question that the onion is still safe to consume, it is advisable to discard it.
Whole onions should be stored in a cool, dry, out-of-the-sun pantry or cabinet. Depending on the storage temperature, they'll survive weeks to months.
Prevent the deterioration of your potatoes and onions by not storing them together. Next to the potatoes, onions will begin to soften and liquefy.
After peeling and slicing an onion, it is recommended to store it in the refrigerator. Any unused onion halves should be wrapped in plastic wrap or stored in an airtight container.
You should also avoid storing onions in the refrigerator, since the cold and humidity can cause them to soften and develop moisture spots.