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How to Tell if Mushrooms Are Expired

Updated June 13, 2017

Eating spoiled food is a major cause of food-borne illness. The common culprits such as milk and meat aren't the only foods that can go bad and make you sick. Though spoilage takes longer, fungus-based foods like mushrooms can go bad, too. With a little information, you can make sure the mushrooms you're eating are fresh and wholesome.

Examine the package for an expiration date. Since mushrooms breathe after harvest, packaging that cuts down on air circulation helps retard spoilage, according to Ramaswamy Anantheswaran, Ph.D., an associate professor of food science in the College of Agricultural Sciences at Pennsylvania State University. Plastic, however, is not foolproof. Do not buy or eat mushrooms past the printed expiration date.

Sniff the mushrooms. Mushrooms sold individually will not have printed expiration dates, and you can use your nose to make up for that. Fresh mushrooms should smell lightly of earth. A sharp, acrid or vinegary smell indicates spoilage.

Wipe the tops of the mushrooms with a paper towel. As with most other foods, water on the surface of mushrooms speeds up the spoiling process. You should get a little dirt or a tiny amount of moisture off the surface of your mushrooms. A slimy or viscous residue means the mushrooms have gone bad.

Cut the mushrooms in half with a paring knife and inspect them. Good mushrooms should have a uniform colour, with the gills a few shades darker than the flesh. Green, blue or white spots indicate harmful mould or bacterial growth.

Tip

Cooking fresh mushrooms in tomato sauce adds a depth of flavour to pasta and pizza.

Warning

Unless you forage with a trained mycologist, never eat wild mushrooms. Many dangerous species closely resemble edible varieties.

Things You'll Need

  • Your fingers
  • Your nose
  • Paper towel
  • A paring knife (optional)
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About the Author

Melanie Greenwood has been a freelance writer since 2010. Her work has appeared in "The Denver Post" as well as various online publications. She resides in northern Colorado and she works helping to care for elderly and at-risk individuals. Greenwood holds a Bachelor of Arts in pastoral leadership from Bethany University in California.