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How to Tell If Mushrooms Have Gone Bad

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Wondering if your mushrooms have gone bad?

It’s good that you’re asking this question! It’s important to be cautious and avoid the unpleasant and potentially harmful consequences of food poisoning.

Don’t worry, we’ve got you covered. We’ve put together this guide to take you through the simple steps to know if your mushrooms are still good or if they already past their prime.

Do Mushrooms Go Bad?

The short answer is, yes.

Both fresh mushrooms and cooked mushrooms can go bad if they are not stored properly or kept for too long a time.

So, when exactly do mushrooms start to go bad?

While mushrooms don’t inherently harbor harmful, disease-causing bacteria the way meat does, they can get contaminated with such bacteria from the soil where they grow, during the harvesting process, transportation, or even at the grocery store.1Betts, R. (2021, March 10). What’s the Potential for Mushrooms to Cause Bacterial Food Poisoning? Rapid Microbiology. Retrieved May 11, 2023, from https://www.rapidmicrobiology.com/news/what-39-s-the-potential-for-mushrooms-to-cause-bacterial-food-poisoning

Bacteria — known for their ability to multiply — can find a breeding ground on mushrooms if they are exposed to any temperature above freezer temperature, or 0°F (-18°C). If contaminated mushrooms are kept for an extended period, they can easily become overgrown with pathogens and pose a risk of food poisoning when eaten.

How to Tell If Mushrooms Are Bad

To identify bad mushrooms, use your senses of sight, touch, and smell.

Bad mushrooms may appear shriveled and discolored, feel slimy and mushy, and smell bad. Discard and don’t eat mushrooms if you suspect that they are bad or spoiled, as they can make you sick.2Government of Canada (2019, December 5). Food safety tips for mushrooms. Food Safety for Fruits and Vegetables. Retrieved May 11, 2023, from https://www.canada.ca/en/health-canada/services/food-safety-fruits-vegetables/mushrooms.html

Look the Mushrooms Over

Start by visually inspecting the mushrooms for any visible signs of spoilage.

Check if the mushrooms appear significantly different from when you purchased them. Look for shriveling, excessive browning, dark spots, or mold growth. These visual cues suggest that the mushrooms may have gone bad and may not be good to eat anymore.

Touch the Mushrooms

Perform the touch test. It will help you determine if the mushrooms are still crisp and fresh.

Gently feel the mushrooms to check for any sliminess or a mushy texture. Fresh mushrooms should have a firm and slightly spongy feel. If the mushrooms are slimy or overly soft, they may be spoiled and are therefore not safe to eat.

Give the Mushrooms a Sniff

Take a moment to smell the mushrooms. You want to find out if they have developed any unpleasant smells due to bacterial activity.

Fresh mushrooms have a mild, earthy aroma. If the mushrooms give off an off odor, it’s a clear sign that they’ve gone bad and may no longer be good to eat.

Will Cooking Spoiled Mushrooms Make Them Safe Again?

Let’s dispel a common misconception that home cooks have when it comes to the safety of cooking spoiled mushrooms.

While it’s technically true that heat can kill bacteria, cooking contaminated mushrooms will not necessarily make them safe to eat again.

Certain bacterial strains exhibit a high resistance to heat, meaning that they may survive the cooking process. Furthermore, even if the bacteria are destroyed by heat, some strains can leave behind toxins in the mushrooms that can just as well result in a foodborne illness.3Food Safety Myths. Washington State Department of Health. Retrieved May 11, 2023, from https://doh.wa.gov/you-and-your-family/food-safety/food-safety-myths

If you’re not sure about a package of mushrooms in your fridge, err on the side of caution and throw them away.

This practice aligns with the fundamental principle of food safety: “When in doubt, throw it out.” This rule serves as a reminder that our health should never be compromised when it comes to consuming potentially spoiled or contaminated food, even if it results in food waste.4Murray, S. (2022, September 26). ‘When in doubt, throw it out’ and other food safety tips for power outages. UF/IFAS Blogs. Retrieved May 11, 2023, from https://www.canada.ca/en/health-canada/services/food-safety-fruits-vegetables/mushrooms.html

How to Store Mushrooms

Fresh Mushrooms

Store whole mushrooms in a paper bag in the refrigerator, where they will keep for 7 to 10 days.5Purdue University. Mushroom. FoodLink – Purdue Extension. Retrieved May 11, 2023, from https://extension.purdue.edu/foodlink/food.php?food=mushroom6Harvard T.H. Chan School of Public Health. Mushrooms. The Nutrition Source. Retrieved May 11, 2023, from https://www.hsph.harvard.edu/nutritionsource/food-features/mushrooms/ Avoid storing mushrooms in airtight containers, as they will collect moisture and turn bad quicker.7Oregon State University. Mushrooms. Store Well Waste Less. Retrieved May 11, 2023, from https://foodhero.org/healthy-food/store-well-waste-less-mushrooms

Sliced mushrooms will last for 1 to 2 days in the fridge. Since sliced mushrooms can last only so long, it’s recommended to use them up the same day or freeze them for long-term storage.

Mushrooms don’t freeze well because they consist of 80 to 90% water.

Even so, if you need to freeze mushrooms, you can clean them with a damp paper towel, then briefly steam or sauté them. Cool the mushrooms before transferring them to shallow, freezer-safe containers and putting them in the freezer.

Remember to write down the date of freezing. While the mushrooms will stay safe to eat indefinitely, they will only keep their best aroma, flavor, and texture for 10 to 12 months.8Mushrooms. StopFoodWaste. Retrieved May 11, 2023, from https://stopfoodwaste.org/tips/store/mushrooms9USDA (2013, May 15). Freezing and Food Safety. Food Safety and Inspection Service. Retrieved May 11, 2023, from https://www.fsis.usda.gov/food-safety/safe-food-handling-and-preparation/food-safety-basics/freezing-and-food-safety

Cooked Mushrooms

Cooked mushrooms are a perishable food product. As such, they shouldn’t sit out at room temperature for more than 2 hours (1 hour on warm days, when the outside temperature is 90°F/32°C and above) and should be refrigerated.

Refrigerate cooked mushrooms in airtight containers, or tightly wrapped in aluminum foil or plastic wrap. Properly refrigerated, leftover cooked mushrooms will stay good for 3 to 4 days.10USDA (2020, July 31). Leftovers and Food Safety. Food Safety and Inspection Service. Retrieved May 11, 2023, from https://www.fsis.usda.gov/food-safety/safe-food-handling-and-preparation/food-safety-basics/leftovers-and-food-safety

Bottom Line

To tell if your mushrooms have gone bad, looks for the telltale signs of food spoilage. Bad mushrooms will wrinkle, become slimy, and develop dark spots or mold growth on the surface.

If you suspect that the mushrooms in your fridge have gone bad, discard them and don’t eat them. Cooking or reheating them won’t necessarily make them safe to eat again, as certain bacteria or their toxins can sometimes survive heat.



Dim is a food writer, cookbook author, and the editor of Home Cook World. His first book, Cooking Methods & Techniques, was published in 2022. He is a certified food handler with Level 1 and Level 2 Certificates in Food Hygiene and Safety for Catering, and a trained chef with a Level 3 Professional Chef Diploma.

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