You can tell mushrooms have gone bad by their appearance, texture, and smell. They may become slimy, shriveled, and occasionally sticky. u003cbr/u003eu003cbr/u003eThey may also have an unpleasant smell, and may have some mold on them.u003cbr/u003eu003cbr/u003eIf your mushrooms are fresh, they should be firm, smooth, and have an earthy smell that is pleasant.