How to know if mushrooms have gone bad

You can usually tell by feeling if your mushrooms have gone bad as they develop a sticky/slimy surface and get darker in color. Once this starts, it quickly destroys them. Once you begin to feel a slime on the mushroom, cook them quickly to extend their shelf life for a few more days.

Eating spoiled or rotten mushrooms can cause gastrointestinal illness and even poisoning. It’s not the mushrooms that will get you – it’s the microbes that eventually colonize and take over mushrooms once they are spoiled. As much as possible, eat fresh mushrooms and try to consume them before they begin to shrivel up.

Eating bad mushrooms could mean the mushrooms were actually of a potentially toxic, wild variety or that the mushrooms were once safe but were eaten long after their prime. However, cooking a poisonous mushroom variety will not remove the toxins, so it’s still incredibly dangerous, and they should never be eaten.

Odor. Mushrooms give off a rather pungent, ammonia-like odor when they are past their best. They can also smell somewhat fishy, too. Anything other than a regular earthy smell is not a good sign.

Store-bought mushroom poisoning is highly unlikely, although eating a bad or spoiled mushroom could cause illness or an upset stomach. If they are left out for hours after cooking before placing them in the refrigerator, for instance, they could cause stomach problems once reheated.

The good news is that if you do happen to eat a bad mushroom, it most likely won’t be a huge deal. Mushroom poisoning from store-bought mushrooms is very unlikely. However, if you eat mushrooms well past their prime, you might get an upset stomach or feel sick.

Get rid of mushrooms that smell sour or fishy.

Fresh mushrooms should smell slightly sweet and earthy, but not foul. If you give them a whiff and they smell fishy or pungent, it’s time to toss them. Discard spoiled food promptly to prevent bacteria and mold growth from spreading to other items in your fridge.

Cultivated mushrooms are usually cooked, which kills any harmful bacteria that may have contaminated them from soil, insect pests, rodents or handling during processing.

Mushrooms and botulism

The conditions in which mushrooms are packaged and stored can also contribute to the growth of harmful bacteria. Storing fresh mushrooms unrefrigerated in an airtight container may promote the growth of harmful bacteria that could cause botulism.

Raw mushrooms and raw mycelium may pose health hazards from harmful pathogens and heat-sensitive toxins—potentially causing red blood cell damage¹, gastrointestinal irritation and allergic reactions, such as skin rashes².