I fried fresh sliced button mushrooms in butter over low heat with no other ingredients. After a short while dark red areas started to appear on the sides of several slices.

I never noticed anything like it before and would be happy if someone had an explanation. Also I would like to know whether or not it is a sign of some sort of danger.

I tried to find information online but the results are mostly recipes and the only instance where someone describes the same, people's responses are not at all helpful (»maybe you cut your finger without noticing«, »maybe you used fly agaric«).

  • Stupid question: Do you have a color vision deficiency? I have a friend who has a mild color vision deficiency and often sees funny colors in food that he fries in a pan. I suspect that the food turned golden brown and the color resembles with red for people with color vision deficiency. Jun 8, 2015 at 9:14
  • interesting approach! but no, haven't noticed anything yet. also, most of the slices were just browning, only a handful (but definitely from more than one mushroom) went clearly red.
    – jshlke
    Jun 8, 2015 at 10:32
  • 1
    I have no idea o.o Do you have any pictures of these mushrooms? Jun 8, 2015 at 18:29
  • 2
    I've seen mushrooms turn a rusty brown or pink color when they oxidize, but never "red". Is it possible that you could provide a picture? It could very well be oxidizing. Heat often increases the rate of oxidation, so its possible that this is what you're experiencing. Does the color go away or become less apparent once the mushrooms are fully cooked, or do they continue cooking into a red color?
    – tsturzl
    Jun 9, 2015 at 0:05
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    I will make an answer to summarize this thread of comments.
    – tsturzl
    Jun 9, 2015 at 15:34

1 Answer 1


According to this article, button mushrooms may turn a pink color if bruised while being stored or handled. This sounds very much like what has happened to you, as you've stated that the mushrooms were old and not stored properly. This is not poisonous or bad to eat by any means, but I understand that one would not want to take the risk, especially when it comes to a fungi such as mushrooms.

For more information on storage, see the article provided above. A short excerpt on storage taken from that source:

Storage - Agaricus bisporus will last longer in your refrigerator than many other mushrooms, usually around a week. It's better to store them in a paper bag rather than plastic. They'll last even longer if you take the time to put them in paper!

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