Egg Science

[A Scottish Chef]

I'm sure I read something on eGullet recently about how exposing eggs to stainless steel for too long turned them green. I'm not absolutely certain however, but, in any event, I'd like to know if this is indeed the case.

If it is so, why does this happen and how best can it be avoided?

[g.johnson]

Stainless steel contains chromium and some nickel. Chromium and nickel salts can be green. Something in the eggs might react with the metals, though it doesn't sound altogether likely. Stainless steel is called stainless for a reason.

[Suzanne F]

Cooking a boiled egg at too-high heat, for too long, can cause the yolk to take on a green cast where it meets the white. Is that perhaps what you're thinking of?

BTW: So what was it that lived under the grill? (I ask since you changed your mind, and your signature )

[maggiethecat]

McChef:

Actually, what I have been told is that silver andcarbon steel should never touch eggs. It does discolour both the egg and the metal.

Stainless steel? Never had a problem.

And, with Suzanne, what was it that lived under your grill?

Edited February 18, 2003 by maggiethecat (log)

[chopjwu12]

i have to say that stainless is ok and that i never had a problem. The green can be one of two things. Ive seen it in a reaction with alluminum pots when the eggs have been cooked to long. But in the case of the improperly cooked hardboiled egg that suzanne described that is a sulfer ring. There is sulfer in eggyolks. So when they are over cooked teh sulfer rises to the surface of the yolk.

[Richard Kilgore]

Another egg science question: Grade A vs Grade AA eggs - can you tell a difference?

[Holly Moore]

Cooking a boiled egg at too-high heat, for too long, can cause the yolk to take on a green cast where it meets the white.  Is that perhaps what you're thinking of?

BTW: So what was it that lived under the grill?  (I ask since you changed your mind, and your signature  )

Pulling out my notes from Food Prep 220 (see first cookbook thread):

Egg whites contain hydrogen sulfide. Egg yolks contain iron. Hydrogen sulfide and iron form Ferrous Sulfide which turns the yolk green where yolk touches white. The longer the egg is cooked the more green Ferrous Sulfide is formed. Also from the notes, the fresher the egg the less likely that ferrous sulfide will form.

[Suzanne F]

Richard K -- one should be able to. AA eggs are the freshest: the albumin sits higher (instead of being spread out and somewhat watery); the yolk sits well on top, in a rounded mound. As time goes on, the egg will kind of sag (rather like us women ).

That said, I don't really know if one could, if not viewing them side-by-side.

[A Scottish Chef]

BTW: So what was it that lived under the grill?  (I ask since you changed your mind, and your signature  )

It's a chiding/piss take comment used by Chefs at CaterinCo to suggest you might want to rush and check on an item being cooked.

Chef A, "Whats black and live under the grill?"

Chef B, "Fuck!"

Chef B hastily moves to grill to discover whether the bread/bacon/steak/sausage/burger/oats/etc are charred to death or the piss taking Chef A has saved the day for him.

Others I have heard include,

Q. "Whats red and black and lives on the stove?"

A. Burnt plum tomatoes.

Q. "Whats yellow and green and lives in the steamer.?"

A. Those damned scrambled eggs I asked about initially.

I had read here, or either from a link here or after searching for something after reading a post here, that the reason the eggs may have turned green could be from too long an exposure to stainless steel. The eggs scrambled in the steamer are cooked in stainless steel gastronorm pans.

I suggested this to my colleagues and they rounded on me to tell me they were simply overcooked. Now I knew about the reaction that Holly described, but I was/am unsure this would be applicable to eggs beaten to be scrambled. I'm thinking I may have come across the information after searching for the McChef wannabe Ferran Adria or in a link to the Fat Duck site. I can't find the site where I read it now!

Edited February 19, 2003 by A Scottish Chef (log)

[A Scottish Chef]

And, with Suzanne, what was it that lived under your grill?

And the reason I changed the signature is the fact I no longer kill things with the grill.

I've finally gotten used to CateringCo style kitchen layout whereby the grill is located 30 yards around a corner from the main cooking range.

It's less than ideal for cooking attentively, but is fantastic for personal fitness.

[Elissa]

aren't copper bowls made for eggs?

[Dave the Cook]

aren't copper bowls made for eggs?

Mostly for whipping egg whites. A copper-related chemical reaction stabilizes the foam, much like cream of tartar does.

[nervousnelli]

I've been told that if you're going to scramble eggs and then hold them for a while (for example, at a lunch buffet) you should add a few drops of citrus juice to them before scrambling. When hard boiling eggs I've found that starting with the eggs in cold water, bringing it to a boil and then turning off the flame and covering and allowing to stand for 10 minutes will produce good results and never a hint of green.

[chopjwu12]

I've been told that if you're going to scramble eggs and then hold them for a while (for example, at a lunch buffet) you should add a few drops of citrus juice to them before scrambling.  When hard boiling eggs I've found that starting with the eggs in cold water, bringing it to a boil and then turning off the flame and covering and allowing to stand for 10 minutes will produce good results and never a hint of green.

yeah thats right about the way to cook hard boiled eggs. But i think teh time is actually 18 to 20 minutes for a fully cooked yolk. Im going to run some tests and find out though.

[Elissa]

a vinegar poach may be the greatest. why?

[Elissa]

haven't found that pressureized steam and eggs go well.

Edited February 22, 2003 by lissome (log)

[Suzanne F]

a vinegar poach may be the greatest. why?

Because the vinegar (acid) helps the white to set faster -- in effect it partially "cooks" the white as soon as the egg hits the liquid, even before the heat works. Same principle as how citrus juice (=acid) "cooks" the fish in ceviche. Something to do with acid denaturing protein, IIRC.

That's also why some instructions say to add a little vinegar to the water for eggs cooked in the shell -- so that if the shell happens to crack, the leaking white will sort of self-seal the break before too much oozes out.

[Elissa]

Do you think tarragon white wine vinegar would be the best choice then? Rice vinegar? Apple cidre?