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I was separating egg whites today and one of the yolks broke and contaminated my bowl of whites. I started from scratch, but I'm wondering if I really needed to; would a tiny bit of yolk (say, 1/8 tspn in 4 egg whites) mixed in with the whites make a big difference?

To provide some context, I was about to whip the whites with castor sugar to make almond macaroons.

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5 Answers 5

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Yes, it matters a lot. When you are separating egg whites, it is for whipping them into a foam. This foam is a protein-based foam, relying on protein ends hooking into each other. Even small traces of fat will prevent the foam from forming. Egg yolks contain high amounts of fat. Once an egg yolk breaks in your whites, you have to start the separation anew, because it can prevent your foam from forming. Also, don't use plastic bowls for whipping egg whites (their surface retains some fat molecules even after washing, giving you a less stable foam) and only whip with a cleanly washed whisk or mixer attachment (not one you have just used for something else, not even if you wiped it clean).

To prevent big mishaps, just separate each new egg in a teacup and only add the new white to the old whites after it has separated cleanly. Else you are in big trouble if you are separating a lot and the last egg contaminates the whole whites with yolk. And a single contaminated egg is easily reused for a quick egg-and-feta sandwich or something else.

Contamination the other way round isn't so worrisome. You still want to work as precisely as possible, as yolk-only recipes will often have somewhat worse texture if eggwhite is included, but small contaminating amounts are usually not noticeable in the finished product, even in foams (zabaglione, mayonnaise). This is because yolk foams are fat-based, and small amounts of protein don't prevent a fat foam from forming.

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Excellent answer. –  Chris Cudmore May 12 '12 at 13:04
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I would add that it is especially important for something like macaroons, meringhe, etc. where a stiff foam is very important. You may get away with it if just lighly beating egg whites for a cake, though. –  nico May 12 '12 at 13:58
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Nice answer. Pastry chefs use copper bowls for making meringues, as copper ions transfer to the egg whites and help stabilise them, preventing overbeating. –  ElendilTheTall May 12 '12 at 18:28
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@ElendilTheTall you don't need copper. Acid does the same job as copper ions. So most recipes call for a pinch of cream of tartar (very weak acid, no taste). And it doesn't color the foam the way copper does. –  rumtscho May 12 '12 at 19:04
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@Cerberus I suspect that it depends on the type of plastic too. My measuring cups seem to be made of PLA or some similar hard plastic, while the plastic which always feels "greasy" is usually nylon-based. But I never tried it myself, only read about the problem in sources I consider reputable (I think McGee mentions it too), and of course for most applications, you don't want the stiffest meringue possible, just soft peaks. –  rumtscho May 12 '12 at 19:06

Before discarding, you can give this a try. Worked for me today (I was making tiramisu).

  1. Lift as much of yellow specks from the egg whites in your bowl as you can and then start beating it, adding little sugar at a time.
  2. Even after beating long enough if you do not see the anti-gravity feature of the meringue, just let your bowl sit undisturbed for some time (maybe half an hour).
  3. Once you are back, you should see a foam-like surface on the bowl.
  4. Scoop the foam up carefully with a spoon (don't dig too deep, else the liquid might come in too) and now hold the spoon upside down.
  5. If the foam doesn't fall off, yippee, there you have your meringue!!
  6. Collect as much of this foam as you can(remember to check for the anti-gravity feature) and add it to your cream mixture (in case of tiramisu), very gently mixing it in. You will find that the cream slowly thickens.

Ofcourse, this method will not produce as much meringue as expected out of x number of eggs, but, it does come in handy.

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There's no cream in a meringue. And I don't really understand how a foam substitutes for one. Can you clarify your answer please? Is this actually a method for recovering a meringue or is it just what it sounds like, some way of reusing the failed attempt? –  Aaronut Sep 3 '13 at 19:16
    
I have done this too. Just whipping what you can whip and scoop out the stiff peaks. –  Mien Sep 3 '13 at 19:46

I know that this question was from over a year ago, but id just like to point out that i make meringues at least once a month and often a little bit of yolk gets in.

This is never a big issue!!I just whisk the egg whites like normal and almost always it is fine.

Good Luck with future meringues!!

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"almost always" and "never a big issue" contradicts itself a bit, I'm afraid. –  Mien Jan 2 at 14:37

I had the same problem this morning as I was trying to make waffles, but I still got stiff peaks. I had a significant amount of yolk in my whites and what I did was I tried to scoop as much yolk as I could out of the whites with a spoon and, even though there were still some wisps of yolk leftover, the whites still became stiff peaks quite quickly (of course I was using the second highest setting on my electric mixer). Waffles were delicious!

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Honestly it doesn't really matter. If you want to separate the yolk, then you should break the egg and then slowly tip the yolk between the two shell halves. The other way is a bit more messy; first rule wash your hands. Then break the egg. Tip it into your hand and then roll it between your hands the white will filter out between your fingers. I have found that the best thing is to have 2 bowls, one for whites and one for yolks. This way if things get messed up then you won't ruin a whole meal.

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