For a confection with so few ingredients—just egg whites, sugar, and perhaps a pinch of acid like cream of tartar—meringues are surprisingly versatile and complex creatures. They can be hard, crisp shells (like vacherins) or cake layers (like dacquoise), or they can be soft, cloudlike toppings for pies and tarts. Meringues can also be troublemakers. They can weep, they can bead, and they can be too soft. As any pastry chef knows, making a light, stable egg-white foam—the basic component of a meringue—is no simple matter.
Beaten egg whites whipped with sugar
A meringue is simply a mixture of beaten egg whites whipped with sugar until the volume increases and peaks form. Egg whites have a superb capacity to foam; as long as certain precautions are taken (see the sidebar opposite), they can increase in volume by up to eight times.
The first step in making meringue—beating air into egg whites—causes one of the egg-white proteins (conalbumin) to unwind, or denature. The unwound proteins link loosely together around the air bubbles, establishing a-foam.
The key during this initial step is to beat the egg whites just until the proteins are loosely linked, which a pastry chef recognizes as the soft-peak stage. These loosely linked proteins allow the air bubbles to expand when they’re heated so the soft meringue can rise until heat sets all the proteins.
If the egg-white foam is overbeaten, however, the protein bonds will tighten and the foam sets even before it gets heated. Then, when it is heated, the foam won’t puff at all in the oven. If the beaten egg whites start to look at all dry, hard, or lumpy (as do the whites in the photo at right), then they’re probably overbeaten.
The right amount of sugar stabilizes the egg foam
Sugar is a vital part of meringues. Besides adding sweetness, sugar helps stabilize the meringue’s structure. When sugar is beaten into an egg-white foam, it dissolves in the protein film on the surface of the air bubbles. This sugary syrup film prevents the proteins from drying out and tightening up too fast.
Once you add sugar, you can beat the egg whites without worrying too much about their getting lumpy or overbeaten. But at the same time, sugar dramatically increases the beating time required to get good volume. Pastry chefs deal with this double-edged sword in different ways: some chefs add sugar to the whites in the beginning, turn the mixer on, and walk away, but most prefer to get some volume and structure in the whites first, and then start adding the sugar.
The proportion of sugar to whites determines the meringue’s texture. When you beat sugar into egg whites, the sugar draws the water out of the whites. Then, when the meringue is heated (either in the oven or by pouring in a boiling sugar syrup), the heat evaporates the water from the sugar-syrup-encased air bubbles, and you end up with delicate, sugar-crusted bubbles.
The more sugar there is in a meringue, the more water can be drawn out and evaporated, and the drier and stiffer the meringue will be. In general, hard meringues require 4-tablespoons of sugar per large egg white. For soft meringues, the traditional formula is 2 Tbs. of sugar per egg white.
A meringue that’s too soft or that can’t hold its shape may simply not have enough sugar. For their cookbooks on healthful eating, Time Life chefs found that they needed at least 1-1/2 Tbs. of sugar per egg white to get a stable meringue.
The solution to weeping and beading meringues
Two common problems that occur with meringues are weeping, which are “tears” of liquid that collect in a puddle under the meringue, and beading, brown droplets of syrup on the outer surface of the meringue.
Weeping is caused by undercooking. If the proteins don’t get hot enough to cook (or firmly set) the foam, it collapses, and the liquid film on the surface of the bubbles leaks out. If a soft meringue on a pie starts to weep after the meringue is baked, the meringue didn’t get hot enough to cook all the way through. It helps to pile the meringue on a piping-hot pie filling rather than on a chilled one. Another trick, gleaned from Roland Mesnier, the White House pastry chef, is to sprinkle fine cake crumbs (nothing fancy—I’ve even used Twinkies) on the hot filling before mounding on the meringue. The combination of crumbs and hot filling can give you an incredibly dry seal between the meringue and the filling.
Lowering the oven temperature and increasing the cooking time can help with weeping, too. Food reaches higher temperatures in the center when cooked at lower temperatures for a longer time. So to get my nine-egg-white-high meringue cooked through, I cook it at a fairly low temperature—300° to 325°F—for 30 to 45 minutes.
For soft meringues that aren’t baked but are just heated by a boiling sugar syrup (an Italian meringue), weeping could be a result of the sugar syrup’s not being hot enough to fully “cook” the meringue.
Beading is caused by overcooking. The proteins tighten and squeeze out water droplets, which brown because of the sugar they contain. Try lowering the temperature or decreasing the baking time, or both together, to solve a beading problem.
You can actually undercook and overcook the meringue at the same time and have both weeping and beading occur. If you pile the meringue on a cool filling and cook at a high temperature (425° to 450°F) for just a few minutes, the surface will have beads from overcooking, and underneath will be puddles of liquid that drained from the undercooked bottom
Everything matters when making meringues
Condition of the eggs
Room-temperature whites whip faster than cold whites. Old egg whites whip faster, and to a slightly greater volume, but fresh whites make a more stable foam that holds up better during cooking.
Fats destroy eggwhite foams, and egg yolks and olive oil are two of the most destructive. One tiny smidge of yolk in the whites, or of grease on the beaters or bowl, can give you a thick, gray mess rather than a light, stable foam.
Type of sugar
For soft meringues, superfine sugar (also called bar or castor sugar) is preferable because it dissolves faster. For hard meringues, confectioners’ sugar will give a lighter result.
Type of bowl
A copper bowl is best, a plastic bowl is worst. Beating whites in a copper bowl seems to help increase the volume during baking. Avoid plastic, which is difficult to rid of trace amounts of fat.
Type of whisk
For hand beating, use a balloon whisk with many tines—more tines incorporate more air faster. For an electric hand mixer, be sure to move the beaters around in the bowl.
How long to beat
Beat the whites first to soft peaks. Then add the sugar, gradually while beating, and beat until the whites are firm enough to hold detailed swirls. It’s imperative that you beat the meringue until it’s very firm.
Avoiding the dreaded shrinking meringue
When meringues are baked in the oven, the tightening of the egg-white proteins causes the meringue to shrink. It also makes the meringue difficult to cut smoothly. My solution to this problem is to add a little cornstarch paste to the meringue. Cornstarch prevents the egg-white bonds from tightening (in the same way that it prevents eggs from curdling in a pastry cream) so the meringue doesn’t shrink. This tender meringue with starch cuts like a dream.
To add cornstarch to a meringue, you should first dissolve it in water (dry cornstarch can’t access the water in the meringue—the sugar has it all) and heat it. Dissolve 1 Tbs. cornstarch in 1/3 cup water and heat it until a thick paste forms. After all the sugar is beaten in and the meringue is firm, keep the mixer running and add all the cornstarch paste, a teaspoon at a time.