I can’t imagine a baker’s kitchen without that little container of cream of tartar on the shelf.
Why? With cream of tartar (a.k.a. tartaric acid, the powdered form of the white crystalline acid that forms on the insides of wine barrels—a natural byproduct of wine fermentation), you can make your own baking powder by mixing 2 parts cream of tartar to 1 part baking soda. Or stabilize whipped cream by adding 1/4 teaspoon cream of tartar to 1 cup of cream before you whip it. Or prevent simple syrup (or other sugar syrups) from crystallizing by adding a little cream of tartar to them while cooking. But there’s another use of cream of tartar—stabilizing egg whites—that will forever raise your game as a baker and dessert maker.
Perfectly beaten egg whites can make the difference between a superbly creamy mousse or Bavarian cream that serves 6 and one that’s too dense (and possibly grainy) that only serves 4! Perfect egg whites gets you soufflés that rise, shapely ladyfingers, successful angel food, and so much more. I’m not exaggerating when I say that cream of tartar can transform a good or even very good dessert maker into a great one—simply by helping you get perfectly whipped egg whites!
If you cook, and especially if you bake or make desserts, you’ve noticed that recipes regularly instruct that we whip egg whites until they are stiff but not dry. But I’ve noticed that even good cooks—because they don’t have a pastry chef or baker’s regular (daily!) experience with egg whites—may not recognize dry, over-beaten egg whites, much less realize the impact it can have on final results. How many times have you tried to fold whipped egg whites into a batter or a mousse and found the foam impossible to fold without stirring and deflating it in the process? Remember the mousse, meant to serve 6, that only filled 4 of the ramekins—and the soufflés that didn’t rise? You all know who you are! Now, let me introduce you to cream of tartar.
More: Alice can make meringues with any amount of egg whites—and you can too. Here are her tips for truly great meringues.
A little acid—like cream of tartar— loosens the egg white proteins and allows them to whip up faster and with more volume. Speed and volume are nice, but the biggest advantage of the acid is that it helps keep the egg white foam moist and elastic, thus sturdier: This allows you fold ingredients into the foam (or the foam into a batter or mousse) easily, with a few strokes of the spatula, without breaking the air bubbles and deflating the mixture.
Elastic foam means the air bubbles in the foam will expand rather than burst when heated in the oven, and it prevents the membrane around each of the bubbles from tightening and leaking moisture. My own less-than-scientific mental picture of the perfect foam is a bowl of microscopic balloons, each blown up just enough so that the latex remains flexible and the balloons are bouncy and resilient enough to be handled or even expanded without bursting! A moist, elastic foam means that soufflés, tortes, and sponge cakes will rise, and soft pie tops are less likely to weep. Cream of tartar doesn’t completely prevent over-whipping—you must still be careful—but it helps tremendously, which is why so many baking professionals use it.
I use cream of tartar as a stabilizer in any recipe that calls for whipping egg whites, even when the recipe doesn’t call for it. I simply add 1/2 teaspoon cream of tartar per cup of egg whites—or 1/4 teaspoon for every 4 egg whites—to the bowl with the egg whites before I begin whipping, and then proceed with the recipe as written. Some of my most respected colleagues use twice as much cream of tartar as I do, so you can choose how much to use.