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Sponge, Genoise, Angel Food cakes, Chiffon, Biscuit (French), and some Flourless cakes are known as Foam, Sponge or Unshortened cakes because they contain a large proportion of foamed eggs and/or egg whites to a lesser proportion of sugar and very little wheat flour, if used at all. Much of the cellular structure of the cake is derived from egg proteins and they are classically leavened by steam and air from beaten eggs. As a result most foam cakes can be described as extremely light and fluffy with good volume and an open, even texture, although textures can vary from dense and spongy, to crispy and dry to melt-in-your-mouth tender, depending on any extra ingredients added. These cakes are typically baked in ungreased (tube) pans so as not to deflate their egg white foams and inverted to cool as a result.
Most foam cakes tend to be drier than butter and oil cakes because they typically have little or not fat, with the exception of the Chiffon Cake and some Genoises. Some liquid fat, vegetable oil, is added during the mixing of Chiffon Cakes, although not in great proportion; the fat used is not to serve for its air holding qualities but rather to coat the flour proteins to prevent gluten formation. This results in an extremely tender cake, adds greatly to the perception of moistness and makes it a good keeper. Melted butter (clarified) is optionally folded into a Genoise cake after mixing and right before baking, adding flavor, reducing dryness and/or increasing tenderness.
|Appearance||Thin, golden brown crust
Uniform crumb color
Rough, slightly cracked top crust
|Texture||Light in weight in proportion to
Finer, even, oval-shaped cells with
thin cell walls
Sugary, slightly sticky crust
Soft crust and crumb
Delicate crumb that is easily
|Flavor||Pleasant, well blended
WHAT MAKES UP A FOAM CAKE?
The main ingredient in all foam cakes are eggs; beaten whole or separated, or in a combination thereof. These recipes begin with the Egg Foaming Mixing Method, which is very different from the Creaming Mixing Method used for butter cakes. Simply put, you can perform the Egg Foaming Method by beating a cracked egg in a bowl with an implement, such as a whisk. The result is the egg's yolk and white mixed together with tiny air bubbles, called an egg foam. Egg foams eliminate the need for much flour, added chemical leaveners (baking powder and baking soda), and the necessity for plastic fat (butter, shortening) for encapsulating beaten air in these cakes.
Beaten eggs and the protein meshworks that result in the egg foam, contribute the main structure, strength, stability, and leavening to their recipes. All parts of the egg can be foamed – separated whites and yolks or whole egg. However, not all parts of the egg are equal in their foam ability; separated whites foam the best, followed by whole eggs and then yolks, only. Separated beaten whites have the best potential to form voluminous (leavening) and stable foams (structures with strength and stability) because of their unique proteins, ample water and lack of fat. At the beginning of creating an egg white foam, an acid, such as cream of tartar (or lemon juice or white distilled vinegar), is added. It is used to lower the pH of the whites, stabilizing them and thus helping to increase their volume during whipping. It also whitens the cake and produces a fine grained texture. (The use of salt, another ingredient long thought as a foam stabilizer, is being debated. I add it in with the flour.)
Sugar is an important ingredient when whipping foams, and is the second main ingredient in a foam cake. By raising the temperature at which egg proteins set during baking, sugar delays coagulation long enough to permit entrapment of optimum air. The resulting cakes have tender texture and excellent volume. In some recipes, part of the sugar is added during the egg foaming process (the other part added with the flour), enabling the foam to be whipped more readily, thus becoming more voluminous and more stable. In Genoise cakes, whole eggs are heated with all of the sugar during the foaming process until they "ribbon" which helps dissolve the sugar better and improves the emulsifying properties of the eggs. As a result, it helps them reach maximum volume when beaten.
The third main and optional ingredient to a foam cake recipe can be a small proportion of high starch flour, typically bleached cake, to further help with the foam’s structure and stability. In some roulades, finely ground nuts and the cocoa particles in chocolate stand in for most or part of the flour. Some foam cakes are made without flour, such as meringues and flourless cakes. Meringues are simply comprised of beaten egg whites and sugar without flour or fat, creating especially strong foams. The ratio of these ingredients, how much beating has taken place and baking at different temperatures and times, meringues can range from soft or chewy to crispy.
If the sugar has been separated in two parts, with the first part being used in the egg foaming process, the second part is combined and sifted with flour (and salt) before it is folded into the foam mixture, so it incorporates easily. This sugar disperses throughout the flour, separating the flour's starch particles and keeping them from lumping when the flour is folded into the foam mixture.
Some recipes contain one or more foams, always with at least one type of egg foam, typically an egg white for structure and leavening. The popular Angel Food Cake is made from a single egg foam (egg whites beaten with sugar) until the eggs increase in volume and then sifting flour over them while folding it in, resulting in a snowy-white, airy, and delicate cake that marries beautifully with fruit. Most angel food cakes have a spongy, chewy quality derived from their relatively high sugar content and the absence of egg yolks. The Sponge cake, for example, can contain both an egg white and an egg yolk foam. This dictates a certain mixing (folding) protocol: the flour is sifted and folded into the yolk only foam, so as to create a batter, and then, the egg white foam is folded in. Its resulting texture is spongy and delicate.
Every egg foam’s capabilities and the resulting cake are, of course, influenced by many factors such as type, proportion and timing of ingredients added during beating, the amount and speed of beating and whether heat is applied, tools used, mixer speeds, egg freshness and size, amount of folding, baking pans and their preparation, baking temperatures and cooling techniques.
Baking Pans and Preparation
Cakes pans for foam cakes have to be prepared in special ways appropriate for each type of foam batter so the egg foams can rise to their fullest and/or not collapse. Fat is the enemy of egg white foams, and the recipes containing them must be baked in grease-free pans. Other cakes, such as the Genoise, comprising both egg white and egg yolk foams, folded together, need not be greased on the pan side, but rather on their bottoms, enabling the egg white portion to do its job fully; this is so the egg foam can rise to its fullest without deflating or slipping from the pan sides because of greasing.
SARAH SAYS: Cupcakes (cup cakes) or small, individual cake baked in a paper-lined, cup-shaped mold, such as a muffin pan, that can be made from many different cake batters, such as Shortened (butter or oil) cakes, as well as Unshortened (foam) cakes. (Petits Fours, also known as Petit Four, are also miniature cakes.) If baking unshortened cupcakes, make sure you know how to grease the cupcake liners.
Temperature / Timing
Typical of foam cakes are they need to be placed in a well preheated oven right away. They need the sudden blast for heat and air to be able to rise fully, and set quickly. It's because of the the nature egg foams - beaten air bubbles have a limited life. Beaten whites will coarsen, settle and separate over time, the result being the loss of precious air bubbles and a poorly leavened cake.
Testing for Doneness
The unshortened cake is baked when its surface is lightly browned and springs back slightly when touched or feels firm. Using a toothpick to test for doneness does not work. Some will sound when tapped on the side of the pan with the handle of a wooden spoon.
Some cake recipes needing to be cooled in their pan upside down, such as Angel Food and Chiffon cakes. This enables their stretchy egg proteins, not bolstered by a great proportion of wheat proteins or highly tenderized, to stretch, not sink and compress as it cools, producing the lightest texture.
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