What effect does cream of tartar have on an egg white foam?

This is one of the most popular questions here on joepastry.com, reader Nance! And no, you definitely can’t make an angel food cake with out it (or some other kitchen acid). But let’s start at the beginning. The reason egg whites whip so nicely into foams is because of the proteins they contain. These proteins naturally occur in clumpy balls. But apply a little shearing force and the proteins uncoil, at which point they begin to bond to one another, forming networks. These networks collect on the surfaces of air bubbles, preventing them from popping. The result is foam.

The problem is that the same whipping action that uncoils egg proteins will cause them to clump back up again if you don’t quit while you’re ahead. The point of no return occurs somewhere right after the stiff peak stage, when the proteins that were arranged in nice regular lattices, bonded elegantly, cradling big bubbles of air…start to lose their mojo.

What happens? In a nutshell, the excess agitation causes the protein molecules to bond excessively to their neighbors and gather together in masses (coagulate). At that point they can no longer do their job on the watery bubble surface. The forces of surface tension start to take over again and the bubbles start to pop. The foam turns grainy, then clumpy, then watery, at which point it’s pretty much useless.

What to do about it? While nothing can ultimately protect an egg foam from too much whipping, there are a few steps you can take to broaden your margin of error. Specifically, you can add various substances to the mixture that preemptively plug up the proteins’ bonding sites. Copper ions serve that purpose very nicely, which is why more than a few egg white whippers like to use copper bowls.

On the less expensive side of the spectrum are some simple additives. Copper ions can be had in the form of a dietary supplement, available at your friendly neighborhood health food store. A somewhat less effective yet much more readily available option is acid in the form of vinegar, lemon juice or cream of tartar. Acids don’t affect the proteins’ bonding sites directly, though by changing the pH of the mixture they increase the number of free hydrogen molecules, and they gunk up the works quite nicely.

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12 Responses to What effect does cream of tartar have on an egg white foam?

  1. Melody says:

    So then, i can add vinegar, lime or lemon juice to egg whites if i don’t have the cream of tartar?

    • joepastry says:

      You can, though the cream of tartar is preferable since it won’t add more liquid to the batter. Also I don’t know how much lemon juice it would take to compensate for at least a full teaspoon of cream of tartar. I expect a fair amount.

      - Joe

      • Linda says:

        Would lemon zest compensate for any of the acid to lessen the need for as much liquid?

  2. Susan says:

    I had to whip some egg whites for a recipe one day. Worried that any invisible fat residue in my (clean) bowl would hinder the volume, I squeezed some lemon juice into the bowl for insurance and wiped it out with a paper towel without rinsing the bowl out. My egg whites seemed to whip so beautifully that particular time that I’ve continued to use that method to clean my bowl before whipping egg whites ever since. I never thought that it might have more to do with the action of the acid on the surface of the bowl than just using a squeaky clean bowl! Do you suppose that the acid residue from the juice on the surface of my bowl might have been enough to produce a noticeable difference? ( btw…I don’t whip egg whites for a recipe often enough to really know that my above method was anything more than a clean bowl, perfect temp egg whites, add acid or a happy combination of the three!)

    • joepastry says:

      I’d say that’s a fair bet, Susan! A small amount of acid is really all you need to stabilize a couple of egg whites. It sounds to me like you stumbled onto a great technique!

      - Joe

  3. Henry says:

    Long time no see Joe! What do you think of Flo Braker’s technique of folding in some confectioner’s sugar along with the flour at the end to tenderise the cake? Not many angel food cakes use two kinds of sugar.
    Another question, and a more important one personally: is it possible to cut down on the staggering quantity of sugar in an angel food cake without turning it into dry rubber? I understand that in the absence of fat, sugar acts to tenderise the cake.

  4. Henry says:

    Oh, also, Flo Braker advises against whipping egg whites to a stiff peak because it would make folding in the flour more difficult and hence more loss of volume. What do you think is the optimal state of the egg white foam for this cake?

    • joepastry says:

      Hey Henry!

      Nice to have you back! This particular recipe is less sweet than many. I’ve seen in excess of two cups of sugar for twelve egg whites. That helps the cake whip up high and gives it a very tender texture, but I can’t take the sweetness. 1 1/2 cups is what I’m accustomed to, but you can cake it down to 1 1/4 cups if you like, much below that I think you’re going to have trouble with both texture and volume….but it would be worth a shot to see, I think.

      Cheerio,

      - Joe

  5. I can’t swear that this 6th century recipe (from Anthimus’ “De Observatione Ciborum”) is the first recorded use of foamed egg whites, but it’s a strong contender:

    Greek afrutum, which in Latin is called spumeum [“foaming”], is made of chicken and egg white. But put in a great deal of egg white, so that it becomes like foam – the dish afrutum – ; thus pour over it prepared gravy and oenogarum in a bowl mixing it so that it makes a little mound. And place the bowl on the coals so that the liquids steam and cook the afrutum. And put this bowl in the middle of a platter and spread over it some unmixed wine and honey, and eat it with a spoon or a tender new growth [sic]. However we usually mix in good fish with this preparation or at least sea-scallops, which are best and sufficiently abundant among us. And of these pure scallops make snowballs.

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