Consuming mushrooms provides several health benefits. According to the Mushroom-Appreciation website, "Most mushrooms provide around 20 to 30 percent of high protein content by dry weight." Mushrooms also are rich in fiber, Vitamin D and other essential supplements. Like all foods, mushrooms can go bad. Consuming spoiled mushrooms can make individuals very ill, so it's imperative to learn the signs that mushrooms that are no longer fit for eating.
Read the expiration date on the packaging, if applicable. Flip over the container or package if you cannot find an expiration date on the top.
Look over the mushrooms for spots. Patches begin to emerge in shades of dark brown and black when mushrooms are no longer fit for consumption.
Feel the mushrooms for a slimy coating. The top part, also known as the head of the mushroom, is predominately where symptoms of slimy spoilage occur.
Inspect the gills underneath the head of mushrooms for darkening. If your mushrooms have darkened considerably since purchase, toss them out.
Observe if your mushrooms appear dry or wrinkly. Feel the stems and heads for folds found on the mushrooms. Wrinkles indicate that the mushrooms are not edible.
Smell the mushrooms for an ammonia-like odor that indicates spoilage. If mushrooms smell differently than an earthy, natural aroma, throw them away.