Foam cakes and sponge cakes are delicate cakes made with little or no fat, such as butter, oil, or shortening, making them lighter and airier than butter cakes.
Most foam cakes recipes have no little or no chemical leaveners such as baking powder or baking soda; instead, they depend on a large amount of either whole or separated eggs that are whipped and filled with air bubbles to provide the leavening ingredient to make the cake rise during baking.
Because foam cakes have a high proportion of eggs to flour, they have a light and spongy texture not found in butter cakes.
The basic types of foam cakes are Angel food, chiffon, Genoise, and sponge cakes with separated eggs.
Angel food cake contains no fat and is made with only egg whites and plenty of sugar to provide a moist and tender extra sweet cake.
Chiffon cakes are made with oil and separated eggs; the oil and egg yolk produces a tender crumb and is beaten.
Egg whites and a small number of chemical leaveners produce a light and airy rise. Genoise is a classic European cake; the eggs are heated with sugar, beaten until thick, and combined with flour.
Separated egg cakes are the typical sponge; the egg yolks and egg whites are beaten separately, then gently combined and folded with the flour. Genoise and separated egg cakes may contain butter to provide a moister and more flavorful crumb.
Foam cakes such as Angel Food and Chiffon are moist enough to be served without soaking syrup added.
Classic Genoise and Biscuit Sponge cakes start off drier but with a sturdy structure, making them able to drink and hold lots of moisture. After cooling, the extra moisture is added by sprinkling a soaking syrup onto each layer.
Soaking syrup is simply sugar and water boiled together, and then a liquor, juice, or extract is added in a flavor that complements the cake.
How to Make a Foam Cake
The creaming step to produce air bubbles is eliminated in preparing the batter for foam cakes. Instead, various techniques are used to incorporate air into the eggs.
The recipe may use whole eggs in Genoise cakes, separated eggs in a classic Sponge cake, or egg whites only, such as in an Angel Food cake.
1. Beating Egg Yolks
Egg yolks will generally need to be whipped before using to incorporate air bubbles before being added to the batter. Place room-temperature egg yolks in a small or medium size bowl.
The recipe may also state to add sugar and flavoring to the yolks. Beat the egg yolks with an electric hand mixer or by hand using a wire whisk.
With a hand mixer, beat for 3 to 5 minutes on medium-high speed until the egg yolk foam becomes thick and lemon-colored and drops in ribbons when the beater is lifted. By hand, this will take a bit longer, depending on how fast and how long your arm can endure.
2. Egg Yolk Ribbon Test
Recipes using beaten egg yolks may state to beat until the yolks drop in ribbons.
Lift the beater 2 or 3 inches out of the beaten egg yolks to test for this.
The yolks should be light in color and fall to the surface in thick “ribbons.”
You usually want a three-second ribbon which means from the moment the ribbon hits the surface until it disappears from sight and sinks back into the body of the foam, you have been able to count one one-thousand, two one-thousand, and three one-thousand.
3. Heating Whole Eggs
To make Genoise cakes, whole eggs, and sugar are first heated over a pan of simmering water to dissolve the sugar. This step also increases the mixture, holding more air bubbles.
After warming, beat the egg and sugar mixture using an electric stand mixer for 6 to 7 minutes, or 8 to 10 minutes if using a hand mixer, until it is thick, light in color, and billowy like whipped cream.
Use the ribbon test to determine if the eggs are sufficiently thick.
4. Beating Egg Whites
Egg whites whipped with sugar form meringue, the basis of many foam cakes. The egg whites usually are beaten until they are stiff but still moist.
Once the egg whites have reached the consistency of stiff peaks, stop beating them. Egg whites that are over-beaten become lumpy and dry lose their ability to retain air, and are difficult to blend with other ingredients.
After beating, egg whites begin to break down very quickly; therefore, they should be beaten at the end of the recipe, just before they are folded into the batter, to retain as much air as possible.
Using a copper bowl to beat egg whites is considered ideal; the copper reacts with the egg whites to produce greater volume, stabilizing the whites to hold their shape better.
However, not everyone has an expensive copper bowl sitting in their kitchen. Stainless steel bowls work just as well as copper, and adding a small amount of acid should generate the same result as a copper bowl.
Plastic and wood bowls should not be used to beat egg whites as they are difficult to completely clean of all dirt and grease.
Aluminum bowls are also not a good choice as aluminum is corrosive and can impart a grayish color.
Glass bowls may work fine for making meringue, but don’t drop the bowl, as there is always a chance of breakage.
The bowl and beaters you are using to beat egg whites must be clean and free of any dirt or grease; there cannot be even a speck of yolk in the egg whites, or the fat from the yolk will prevent the egg whites from expanding to a whipped texture.
You can beat the egg whites by hand with a wire whisk; however, using either an electric stand mixer or a hand mixer is far easier. Use room-temperature egg whites and use a large size bowl.
Beat egg whites starting with an electric mixer on medium-low to medium speed. The whites will look frothy at first, with bubbles forming. Cream of tartar or lemon juice is added at this stage. Increase the mixer to medium to medium-high speed.
As you continue beating, soft peaks will begin to form; soft peaks gently droop when the beater is lifted. If the recipe adds sugar, add at the soft peak stage, adding the sugar one tablespoon at a time or in a slow, steady stream while continuing to beat the egg whites.
Also, add any flavorings at this point. Continue beating the egg white mixture on medium to medium-high speed until stiff peaks form; stiff peaks will look like a soft glossy meringue and hold their shape when the beater is lifted.
Whipped egg whites are often used to leaven and lighten cake batter; however, whipped egg whites alone cannot provide support for the trapped air in the cake.
Therefore if no whole eggs, yolks, or unbeaten whites are used in the batter, the cake will rise beautifully in the oven and then collapse as soon as the cake begins to cool.
To prevent this collapse, whole eggs or egg yolks are typically added to the batter before the whipped egg whites are folded in.
For cakes made with little or no flour, more egg yolks are generally needed to support the cake. The cake will still probably fall a bit when cooled, resulting in a moist and tender cake.
5. Folding Ingredients
Folding is a technique for blending two mixtures and is used when one of the mixtures is fragile or needs special care to prevent the mixture from deflating.
Generally, the lighter mixture, such as egg whites or whipped cream, is folded into the heavier mixture, such as chocolate or flour.
Recipe directions may also specify folding ingredients such as flour, chocolate, nuts, and fruits into a batter to avoid over-mixing.
When folding in egg whites or whipped cream, the recipe directions may specify to first fold a partial amount to lighten the batter, and then the remaining egg whites or cream is folded in.
Spoon the light mixture on top of the heavier one. Using a balloon-type whisk or large rubber spatula, first cut down through the center of the batter. Use a circular motion with your arm and sweep the whisk or spatula toward you under the batter, across the bottom of the bowl and up the side to the top of the batter, then down through the middle again.
Continue this circular motion, rotating the bowl slightly each time.
Occasionally run a spatula around the inside edge of the bowl so that all of the ingredients get fully incorporated. It may take 2 or 3 complete 360-degree turns of the bowl to fold the ingredients completely; stop when no dry particles are left.