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The Party That Is Egg Foam

By Brian Geiger, contributor

February 12th, 2009

Kitchen Mysteries is a weekly exploration of oddities surrounding cooking and food. They could be recipes that fail when they shouldn't, conflicting advice from different sources, or just plain weirdness. If it happens in a kitchen, and you're not sure why, send a tweet to The Food Geek to find out what's happening.

In response to last week's article about stabilizing whipped cream, Friend of the Food Geek hkmouse asked on my web site,

Would cream of tartar work as a stabilizer?

The short answer is no, not with whipped cream. Cream of tartar works as a stabilizer for egg foam. The techniques mentioned for stabilizing whipped cream will stabilize egg foam as well, but it doesn't work the other way around. In order to know why, we'll have to explore what an egg foam is.

If you take a glass of water and a drinking straw, and instead of drinking through the straw blew into it, you would generate a bunch of bubbles. I suspect you've done this before, and you may very well have delighted your parents with seemingly endless displays of your bubble-making skills.

The thing about those bubbles is that they don't stick around very long. On the one hand, this is great because homes all over the world aren't filled with bubbles created by bored children. On the other hand, foams are handy in cooking. If we went back to the first hand, we'd mention how unsanitary a foam created by blowing bubbles into the foaming liquid would be for cooking. Fortunately, there are better (and cleaner) ways.

Because eggs, even egg whites, are filled with many chemical goodies, making an egg white foam is an involved affair. The first thing that has to happen is the water in the egg whites has to be convinced not to collapse so quickly. Water really likes water. Water likes water even more than sugar likes water, and that's a lot. 

When water gets near something else, like air, it tends to cling to other water molecules. This is called the surface tension, and it's what allows bubbles to form in the first place. With pure water, though, it quickly tires of the "being friendly with the air molecules" game, and goes back to gossiping about air's poor grooming habits with the other water molecules.

The problem is that egg white foam is a party, and for a successful party, you need everyone mingling and chatting amongst themselves, not huddling together in their own corners. Egg whites have most of the elements of a successful party, but encouragement is still needed. 

The first thing that egg whites do to their water is to mellow water out and convince it that hanging out with air isn't so bad. It points out that air has some funny jokes, and really is kind of cool if you take the time. That sort of thing. It reduces the surface tension. You can see this when you first start to whip the egg whites, and bigger bubbles form and just sit there rather than collapsing immediately.

The whisk is the host of this party, mingling among the guests and convincing them to mix. Pulling some air over here, some water over there, and saying "Hey, you both like golf! Tell him about the time you sank that hole in one next to Tiger Woods," or similar.

So you have your first stable bubbles from basic introductions, which is cool but you need more. So, as you go through with the whisk, some of the proteins start to unwind. They take some effort, though, so you have to physically pull them off the couch and get them working. Because sometimes that's not enough, the whisk creates a conga-line of air and water molecules, and the some of the proteins unfold and get seriously into this conga line.

What you've made here is the basic egg foam. It will go for a while, certainly much longer than a cream foam, but it's not a serious party yet. There are still a bunch of people curled up on the bean-bag chairs reading books, some are playing video games, and honestly you can only do a conga line for so long before everyone is exhausted and collapses into a heap. That's when you over-whisk your foam and it breaks.

There's one protein in egg whites that is very prominent but terribly resistant to the hosting abilities of your whisk to mix and match: ovalbumin. Ovalbumin comes to the party to eat the food and sit around, but it doesn't contribute much to the festivities. The ovalbumin basically keeps its coat on so that, whenever it's ready to go, it doesn't have to ask the host to get its coat, it can just leave whenever.

The trick is to turn up the heat and cook the foam a bit. This does a couple of things. First, it convinces the ovalbumin to ditch the metaphorical coat, stretch out, and really join the party. With all the ovalbumin contributing, the party becomes quite permanent. The other thing it does is convince whatever water isn't currently involved in mingling with other protein or air or someone to just take off and evaporate.

Still, heating up the party might not be what you need for your dish. If you want to keep the party going but not change its texture quite so dramatically, you'll want to bring out the "special punch." For proteins, this means acid.

From a molecular standpoint, protein uses sulfur to hold hydrogen like you might hold on to an appetizer. After a while, though, the appetizers run out, and protein uses the free hand to grab the hands of other protein molecules, so that they form tight clumps of proteins, which ruins our party mix. Acids ensure that there are lots of hydrogen ions free for the taking, like glasses of special punch. This keeps the hands busy and prevents them from making Sulfur-Sulfur bonds, thus preserving the party.

Cream of Tartar is an acid, which is why it acts as a stabilizer. It keeps the protein's sulfur "hands" occupied holding drinks and consequently encourages the sociability of the protein with the other molecules. Lemon juice would also work.

However, if you add an acid to cream, it will just cause it to curdle, which is good in some cases, but bad for whipping. By and large, you'll probably want to avoid that. Still, now you know how to have a successful party and/or keep an egg foam stable.

posted in: Blogs, food geek, egg, acid, meringue, foam, egg whites, whisk, cream of tartar
Comments (6)

user-563676 writes: I agree with food geek. I truly appreciate the attempt but personifying the elements of egg foam was distracting.... and a bit frustrating to get through. Thanks for the simple, more direct version.
Posted: 2:43 pm on December 2nd

Coco_Bean writes: I loved the post. I am a molecular biologist fresh out of school, but for exams I would make little stories like this to remember complex pathways or protein associations. Science is fun, but sometimes it needs a literary boost! Posted: 11:22 pm on March 4th

hkmouse writes: Thanks so much for an answer that was as entertaining as informative, especially for someone who doesn't have much experience with cooking besides following a recipe! Posted: 9:37 pm on February 18th

TheFoodGeek writes: Is it that hard to follow? My apologies.

The short form is that basic whisking mixes in air and starts to stretch out some of the protein molecules. The protein molecules form a mesh around the water, which surrounds the air. If you over-whisk, then the proteins coagulate and the water and air fall out.

If you want to stabilize the foam, you can cook it. Adding heat causes the protein ovalbumin to unfold, which increases the number of proteins immensely. It also causes a lot of the water to evaporate.

The proteins tend to connect to each other by losing the hydrogen in the sulfur-hydrogen bonds and forming sulfur-sulfur bonds. The more sulfur-sulfur bonds you have, the more intra-protein connections you have, which means the proteins are coagulating, which causes the water to fall out and the bubbles to collapse.

Adding an acid increases the number of hydrogen ions in the mix, so if one of the proteins lose one, chances are another one will reattach itself to the opening before another protein molecule with a loose sulfur molecule comes along to attach itself. As cream of tartar is an acid, it fulfills this role. Posted: 5:59 pm on February 18th

foodgeek writes: I appreciate that you wanted to "dumb down" the stabilization technique, but I thought your explanation was a little difficult to follow. You seemed to rattle on and on about nothing. It would've been easier to follow if you had just given the bare facts. A little science never kills anyone. Posted: 4:07 pm on February 18th

jfield writes: I love the way you explain things. Why hold this knowledge sacred for the few in the know? That's what I love about Fine Cooking--it's the only food mag I subscribe,too. Thanks for making food accessible to all:) Posted: 11:22 am on February 13th

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