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.
So then, i can add vinegar, lime or lemon juice to egg whites if i don’t have the cream of tartar?
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
Would lemon zest compensate for any of the acid to lessen the need for as much liquid?
I have three recipes for Pavlova. Two ask for vinaegar. Of those
two, one cornstarch, the other cream of tarter. The third, (MarthaStewert) has neither. Whattodo? for the best results… other than making 3 Pavlova?
Hehe, hey Jackie!
Do both the cornstarch and the vinegar, especially if this is a first time. The acid will help ensure a high whip and the cornstarch will help prevent weeping. Have fun!
– Joe
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!)
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
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.
Hey Henry!
I’m not aware of that, but I’ll have a look. It’s hard to imagine it making much difference…but who knows, maybe it does!
– Joe
http://www.finecooking.com/articles/angel-food-cake.aspx
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?
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
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:
Jim, as always, I thank you.
– Joe
First time at this site. I like the layout and simplicity. I like the combination of the chemistry and theory. I’ll be back.
First time at website. I’ll be back. I like the theory, simplicity of the answers and comments.