Mushrooms are an edible fungus with a rich, earthy flavor. There are several varieties of wild and cultivated mushrooms that you can use fresh or dried to prepare tasty and nutritious meals. Exotic mushrooms, such as maitake and shiitake can be found dried rather than fresh, unlike white mushrooms such as button mushrooms and cup mushrooms, which are widely available fresh. Fresh white mushrooms have a short shelf-life and degrade easily in the presence of light, heat and air. Carefully inspect white mushrooms when purchasing and before cooking, to determine whether they are safe for consumption.
Examine the color and texture of the white mushrooms. Mushrooms that are old and spoiled due to dehydration have a dried, grayish tinge and are shriveled. White mushrooms should be unblemished with a smooth texture and bright white color.
Check the cap of white button mushrooms and cup mushrooms. Turn the mushrooms over to examine the caps. Open caps indicate that the mushrooms are old, whereas closed caps are a sign that the mushrooms are young and tender. Mushroom caps open up as the mushrooms age.
Observe the surface of the white mushrooms. If you notice mold and a thin layer of slime covering the mushrooms, they are spoiled.