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One of the greatest feats of culinary magic is taking a few egg whites and whipping them into a billowy mound of cloudlike foam that fills the entire bowl. A range of recipes—from soufflés to angel food cake to lemon meringue pie—rely on whipped egg whites. But they don’t rely on whipped egg whites alone: Stabilizers are key.
There are a few different ways to stabilize whipped egg whites. Sugar and cream of tartar are two of them. When writing about egg white stabilization for a chapter in The Science of Good Cooking, Associate Editor Dan Souza and I spent a good amount of time brainstorming the best way to show, not just tell, the story of this science. But before we get too deep into the complexities of cream of tartar, let’s start simple: Egg whites. What’s even going on when you whip them up?
As an egg white is beaten, its proteins unfold and bond to create a meshlike network. This network coats and reinforces the surface of the air bubbles produced by the whipping. (Egg whites are composed of about 90 percent water, so these air bubbles are really floating in a sea of water.) These unfurled proteins actually increase the viscosity of the water immediately surrounding the air bubbles, enhancing their stability.
As the whites are beaten further, more air bubbles form and more proteins bond to coat and reinforce them. Eventually the whole mix puffs up and takes on the firm texture of shaving cream.
As a rule, whipped egg white foams are temporary things. The water surrounding the air bubbles will eventually succumb to the force of gravity and begin to drain away, causing the foam to separate and release its liquid. The goal? To delay this as long as possible.
Here’s where stabilizers come in. Sugar works by slowing down the drainage of moisture from the film surrounding the air bubbles in egg foams, helping the whites to remain stable, as well as to achieve maximum volume. But when it came to our experiment, Dan and I decided to concentrate on another stabilizer: cream of tartar, an acid that alters the electric charge on the proteins of the egg white, in turn reducing the interactions between protein molecules. Because this delays the formation of the foam, whipping takes longer but also results in a much more stable foam.
In the end it was pretty simple: Dan whipped up some egg whites with—and without—cream of tartar. We sat back and watched what happened.
Dan beat eight batches of four egg whites in a stand mixer until they achieved stiff peaks.
To half of the batches he added ¼ teaspoon of cream of tartar before whipping, while the others he left plain.
After transferring the foams to funnels set over beakers, Dan collected the water that dripped out for an hour.
The whites whipped without any stabilizers lost 23 grams of liquid on average.
The whites stabilized with cream of tartar lost less than half that amount, about 10 grams on average.
The interesting thing is that the foams made with and without cream of tartar didn’t look different—both were light and fluffy and held their stiff peaks. But they were certainly different inside, releasing a drastically different amount of liquid with time. Without stabilizers the egg foam oozed liquid, leaking at a pretty steady rate. Not so the foam with cream of tartar. While that may not make much of a difference in the texture of foams sitting in funnels, it can be a deal breaker when baking, causing weepy meringues or baked goods that deflate disastrously in the oven. And nobody wants that.
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Got any egg-white–whipping questions? Leave ‘em in the comments.