General Question

josie's avatar

What makes hard boiled egg yolks turn grey around the edge. And while we are all here, is it grey, or gray?

Asked by josie (27501points) February 5th, 2013

I occasionally eat a hard boiled egg as a quick “to go” snack or on a salad. It is really the only time I eat eggs so I boil up a dozen and keep them in the refrigerator for a couple of weeks until they are gone. I notice that some of them, I figure the older ones, turn grey around the edges of the yolk. They must not be rotten, because I eat them and nothing bad happens. But why does that happen. Why do they turn grey? Or do they turn gray?

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22 Answers

thorninmud's avatar

It’s caused by overcooking. It’s unsightly, but not harmful.

English (and commonwealth) yolks turn grey, while American yolks turn gray.

Blondesjon's avatar

God I am so sick of this discussion! Who cares if eggs are gay? It’s the eggs choice what it wants to do in the bedro . . .

Oh shit, my bad. It’s because they are overcooked and the correct spelling is monochrome.

gasman's avatar

I think grey is preferred in British usage/spelling (including Canada), while gray is preferred American. Either is correct.

Buttonstc's avatar

It’s due to the sulphur coming to the surface of the yolk .

And even tho you didn’t ask, there’s a way to avoid it. First, donth cook them for too long. 10–15 mins is sufficient.

Secondly, as soon as you take them off the stove, immediately dump out the hot water and surround them with icy cold water and leave them there till they’re cool enough to handle..

That’s Julia Child’s method and it works every time. No more grayish green ring.

CWOTUS's avatar

The way I learned to cook them was to bring them to a boil, starting from cold water, and then turning off the heat and letting them soak in the boiling water as soon as the rolling boil starts. I only rinse them under cool water enough to be able to handle them while I scoop out the delicious insides, so they’ll still melt the butter.

Oh, and what others said about overcooking, sulphur, okay to eat, and grey or gray.

augustlan's avatar

I found a method that works perfectly every time. I know it sounds silly, but follow the steps exactly, and you’ll never see grey/green in your hard boiled eggs again.

Put the eggs in a largish pot, cover with COLD water to about an inch over the top of the eggs. Bring to a boil on high heat. Once you have a rolling boil (large bubbles popping frequently), immediately remove from heat and cover the pan with the lid. Let sit for 15 minutes, drain and rinse in cold water immediately until eggs are cool to the touch. Perfect every time.

I know “gray” is American, but I prefer “grey”.

Edit: Or, you know, what @CWOTUS said. :p

zenvelo's avatar

It’s Grey if you are Zane-y

Bellatrix's avatar

Don’t leave them sitting in the hot water after you have cooked them. That will stop this happening.

ragingloli's avatar

Letting it cook for too long, it can also turn dark blue/black.
And it is spelled “grey”.

bookish1's avatar

I had no idea why they would turn gris. Thanks for asking!
I recently began putting the eggs into an ice water bath after cooking them, and have never had this problem since.

WillWorkForChocolate's avatar

Because they’re overcooked, like ^^ the others have mentioned.

And I’ve used both gray and grey. I tend to use whichever one I’m in the mood for at the time. :D

JLeslie's avatar

As far as I know grey and gray are completely interchangeable, even here in America. I use both.

I’m going to try @augustlan‘s perfect hard boiled egg recipe.

Sunny2's avatar

My spell check doesn’t approve of grey. I couldn’t care less. I prefer grey and I’ll use an e in knowledge or judgment or not or not. I have free choice in the matter.

Soubresaut's avatar

Well what everyone else said—cooked/heated too long.
The way I’ve always known to hardboil eggs is to start them with the water cold, and turn off the flame when the water boils, too.

Just another comment, and though I’m not sure why this is, it seems to be true from my experience—older eggs are actually better to hardboil, particularly if you want them to look pretty when peeled—they peel easier. The fresher the egg, the more the shell sticks and the more the egg gets all mangled. (Anyone know why this would be true? I’ve always just likened it to how overripe fruit is better to bake with, but I know the actual reason has very little to do with ripe fruit.)

I write ‘gray’ ‘cause I’m from ‘merica, but I always want to write ‘grey,’ I think the word looks prettier with an e.

Buttonstc's avatar

Here’s why older eggs peel better. Even tho it’s solid, the shell is semi-permeable so that moisture is lost over time. That’s why the air pocket is larger on the fatter end (and that’s the best place to begin peeling because of that).

As the egg loses moisture, that thin membrane surrounding the white shrinks back from the shell and thus makes it easier to peel the shell away.

harple's avatar

Grey is the colour’s spelling, whilst Gray is the surname’s. :)

Sunny2's avatar

^^ That’s interesting! Thanks for the info.

JLeslie's avatar

America has tons of people with the last name Grey.

Sunny2's avatar

^^ Perhaps we imported them from the British Empire.

JLeslie's avatar

@Sunny2 Maybe they mispelled the surname at Ellis Island. Happened a lot.

Sunny2's avatar

^^^But there are no scz’s in Gray or Grey.

JLeslie's avatar

What do you mean? Are you trying to say the hungarians had more trouble getting their names spelled right? Or, maybe you mean Russians or the Polish? I think Hungarian for SZ. LOL. My married name has a Z in the middle. When my FIL was born the hospital worker spelled it incorrectly, she spelled it phonetically in Spanish (he was born in Mexico). He was the only sibling of 8 who had all his documents wrong. When he got married the guy who wrote the marriage license wrote it correctly when my FIL told him his license was incorrect. So, he was the only one in his family of his wife amd three children who had his surname spelled incorrectly. I finally helped him with the paperwork here in America to change his name. But, he lived even here for years with the wrong name.

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