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Sponge, Genoise, Angel Food cakes, Chiffon,and some Flourless cakes are known as Foam, Sponge or Unshortened cakes because they contain a large proportion of foamed eggs to a lesser proportion of sugar and very little wheat flour, if used at all. These cakes typically contain little or no added fat and some are baked in ungreased (tube) pans and inverted to cool as a result. Foam cakes are classically leavened by steam and air from beaten eggs and are extremely light and fluffy with good volume and an open, even texture. Although, some recipes can be dense and spongy or crispy and dry to melt-in-your-mouth tender, depending on extra ingredients added.
|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
All foam cake recipes begin with the Egg Foaming Mixing Method, which is very different from the Creaming Mixing Method used for butter cakes. Both mixing methods serve the important purpose of creating millions of air bubbles, for eventual leavening and tenderizing, however, what sets foams cakes apart are their egg foams. Beaten egg proteins contribute the main structure, strength, stability, and leavening to their recipes, especially egg whites, eliminating the needed for much flour, added chemical leaveners (baking powder and baking soda), and the necessity for plastic fat (butter, shortening).
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. 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 are the best, followed by whole eggs and then yolks, only. Separated beaten whites have the best potential to form voluminous and stable foams(structures) because of their unique proteins, ample water and lack of fat.
When part of the sugar from the recipe, the second main ingredient found in a foam cake, is added during the process, the foam can be whipped more readily, can become more voluminous and more stable. With egg white foams, an acid, such as cream of tartar, is also added. Every egg foam’s capabilities are, of course, influenced by many factors such as type, proportion and timing of other added ingredients during beating, such as sugar, cream of tartar (and, being debated, salt), the amount and speed of beating, tools used, mixer speeds, egg freshness and size, whether heat is applied, amount of folding, baking pans and their preparation, baking and cooling techniques.
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. Before being folded into foam, the flour is always sifted so it incorporates easily.
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.
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. For example, "low sugar/egg white ratios and high citric acid(cream of tartar) levels increase meringues air phase; Low sugar/egg white ratios and high citric acid levels determine softer texture; Dry and frozen egg whites and egg whites from old eggs had the worst mechanical performances." (Journal of Food Engineering, September 9, 2011.)
Flourless cakes generally have a creamy or silky textures; it’s because they are comprised of just egg foams (usually whole egg and egg yolk) with lots of added fat, from sources such as yolks, butter, cream cheese, cream or sour cream. They can be baked or unbaked. Baked flourless cakes include baked cheesecakes (more so known as custard) and flourless chocolate cakes. Unbaked flourless cakes, can also be cheesecakes as well as mousse cakes, which are typically molded in a dessert ring or springform pan then simply chilled before unmolding. They often have a crust or bottom layer that's baked before the mousse is added. Sometimes other foam cake layers, such as genoise or biscuit, are alternated with the mousse.
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.
Egg foams, along with their other ingredients, create exceptional protein meshwork structures, which hold the cake together, enabling them to be used in many application; they have the ability to not disintegrate when flavored with light brushings of soaking syrups, in which equal parts of sugar and water are brought to a boil and then flavored with liqueurs or extracts; Some can baked in cake pans and can be easily cut crosswise into layers and filled or used as a base for another recipe; Thinly baked foams cakes can be tinted, cut into strips without falling apart, and be bent around fillings without cracking, such as roulades, perfect as a decorative encasement for a strawberry mousse or chocolate ganache. Foam cakes, especially Angel Food, tend to have a subtle and sweet fragrance to them, making perfect to serve with vibrantly flavored fruit or chocolate sauces, whipped cream and fruit.
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.)
OTHER TIPS AND 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, 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.
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.
To remain that way once cooled, 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.