Check the expiration date on the olive can or container. If the expiration date has already passed, the black olives could be bad.
Smell the olives. If they do not have a smell or they smell metallic or unpleasant in some way, they are probably bad and should be thrown out.
Examine the olives. If black olives have white fuzz on them, seem overly greasy and slimy or look patchy and discolored, they are bad.
Read more: How to Tell If Black Olives Are Bad | eHow.com http://www.ehow.com/how_6908065_tell-bla...
Of course, olives last for a shorter period of time if they are not stored properly. But remember, olives, like a lot of other fruits, usually have a best before date and not a use by date. Because of this distinction, you may safely use olives to compliment your favorite meals even after the best before date has lapsed.
How to tell if olives are bad, rotten or spoiled?
Practicing proper hygiene and food safety discipline will help prevent food borne illness. Your sense of smell is usually the best way to tell if your olives have gone bad. The olives will begin to have an odor if they are going bad. Their texture and color may also change and they may develop mold if spoiled. If the top of the lid on the jar or can is rounded and dome shaped instead of flat across, the olives have most likely gone bad probably because the jar/can was not sealed properly. If you open the jar and do not a hear the normal pop then the seal had been broken. There are, of course, certain health risks associated with spoiled olives, so always remember to practice food safety and enjoy your olives prior to the eat by date.
How to store olives to extend their shelf life?
Proper food storage is the key to extending the expiration date of food. You can help olives stay fresh longer by storing them unopened in the pantry where the temperature is always less than 75 degrees Fahrenheit. Once opened, the olives should be kept in the fridge, fully submerged in their liquid. Do not store open cans in the fridge, place the olives and liquid in a jar or plastic container before putting them in the fridge. Some benefits of proper food storage include eating healthier, cutting food costs and helping the environment by avoiding waste.