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A baked product may contain:
- Only gluten, such as pastry and biscuits;
- Mostly egg proteins, such as angel food or sponge cakes; and,
- A combination of gluten and egg, as most baked products do.
Eggs contribute to the structure of a baked product. They do this through their contribution of heat denatured proteins, steam for leavening or moisture for starch gelatinization. Egg yolk is also a rich source of emulsifying agents and, thus, facilitates the incorporation of air, inhibit starch gelatinization and contributes to flavor.
Wheat is the only grain with significant amounts of gluten-forming potential. It also contains starch which gelatinizes (absorbs water) and stabilizes the structure. Other grains like corn and oats, and therefore products like cornmeal and oatmeal, do not create gluten in a batter. They provide only flavor and bulk, and must be mixed with wheat flour for strength.
WHEAT FLOUR, WATER AND GLUTEN
Classification of Batters and Doughs (ratios):
Two proteins found in wheat flour, glutenin and gliadin, form an elastic substance known as gluten when stirred with moisture. There are as many as 30 different types of protein in wheat, but only these two have gluten forming potential. When wheat flour is moistened and manipulated through stirring, beating and kneading and/or handling, these two proteins grab water and connect and cross-connect to form elastic strands of gluten. If a flour has a lot of these proteins, it grabs up water faster, making strong and springy gluten.
SARAH SAYS: Flour contributes protein and starch to a baked products structure, the protein primarily being gluten. Flour may contribute protein and sugar for the Maillard reaction and/or yeast food for biological leavening.
The magical and elastic gluten network that forms serves many functions in a recipe. Like a net, gluten traps and holds air bubbles. They later expand from the gas from the leavening when a recipe is baked, causing the dough or batter to rise. During baking, the stretched flour proteins (gluten) becomes rigid as the moisture evaporates from the heat of the oven, and sets the baked goods' structure. The viscoelastic properties of gluten provide the perfect combination of elasticity and rigidity by expanding with the gas while still holding its shape. No other grain has been able to replace this function of wheat in baking.
Flour's strength is determined by its gluten content, the amount of liquid and mixing -- all work in concert together: if mixed too much, the cake texture toughens or too little, the cake falls. If the gluten is too strong for a recipe, it toughens and may not rise. If there is too little gluten, the recipe will collapse when taken from the oven or be mushy. Or, if you have the right amount of gluten and stir it too much, your recipe will be tough and dry. The recipe will direct you on which type of flour to use, which corresponds to a gluten protein %. That's why when you substitute one flour type for another, the recipe is always affected no matter how much or little you stir the batter or dough.
Every recipe is written with a specific flour in mind to give the best results: Breads rely heavily on gluten for structure, cakes to a lesser extent, and cookies almost not at all. Gluten also allows you to roll out pastry into thin sheets that don't fall apart.
SARAH SAYS: Recipes commonly use all-purpose flour, which has a moderate gluten or protein content. For a lower gluten content with a more tender outcome, I use whole wheat pastry flour or cake flour. High-gluten flours, such as bread and regular whole wheat, as well as a moderate one, all-purpose, are typically used in yeast breads where a strong framework is desirable. But, in cakes, quick breads and pastries, a high protein flour makes a tough baked good.
|What is Needed||Recipe||Flour||Information||Too Much Gluten|
|Very Weak Gluten||Cake Batters||Cake||A very weak gluten structure forms from the flour and gentle mixing techniques. It holds in the steam from baking, which makes it rise, giving it structure.||Tough, heavy cake|
|Weak Gluten||Pie and Tart Crust Dough||All Purpose and/or Cake||Cold fat is first incorporated, and then the liquid is mixed in. Gluten holds the dough together and traps the steam from baking. Resting and chilling relaxes the dough and is recommended after mixing, rolling and forming.||Heavy and tough|
|Moderately Strong||Puff Pastry||All Purpose||During rolling and folding, the gluten develops. It helps push the layers upward and away from each other during baking. Resting and chilling relaxes the gluten and is recommended after turning.||Difficult to roll and fold, as well as roll out. Tough and distorted after baking.|
|Strong and Very Strong||Bread Dough||All Purpose and/or Bread||During mixing and kneading of the dough. Shaping with too much added flour also creates gluten. That's why it's best to handle the dough gingerly and not to add in too much extra flour when kneading.||Won't rise as well, tough and dry|
When flour is milled, it is classified according to the ratio of its gluten forming proteins to starch. The protein content of a flour affects the strength of a dough. Depending on the type of wheat and where and when it was planted, the resulting flour can be high-gluten (milled from hard winter wheat), low-gluten (from soft spring wheat), or moderate (a combination of the two). All-purpose flour in the North has a high protein count; the one sold in the South is low-protein. Hard wheat, mainly grown in Midwestern U.S. has a high protein content. Baked goods made from high-gluten flours have a firm crumb; low-gluten flours give more tender results, and goods made from flours with a moderate gluten content fall somewhere in between.
The percent protein in flour is a factor when baking (so is altitude): Gluten gives a framework to a baked good by swelling as they absorb water, some flour types absorbing faster than others. A higher-protein flour absorbs more moisture than a lower protein flour. Baker's have blamed the difference in absorption on humidity which only makes a minute difference. Instead, a flour's protein level directly affects the ratio of wet ingredients to dry.
For example, a batter made with 2 cups of high-protein flour absorb 1 cup of water to form a soft, sticky dough. The same recipe made with 2 cups low-protein flour and 1 cup water make a thick soup. It takes 1/2-cup more low-protein flour to get the same consistency as the high-protein flour.
When recipes are written, one type of flour in used and the person baking it uses another. That's because they probably live in different areas of the country or their flour brand is milled in different places.
The more that the flour and moisture are stirred or handled, the more the gluten strands strengthen and toughen. That's why many recipes say not to overmix them. Fat, which is not present in reduced-fat baking in traditional amounts, plays an important role in coating the proteins in flour, minimizing their contact with moisture, and shortening the gluten's development. Without the fat lubricator, the gluten strands form more readily. That is why it is very important to never overmix a reduced-fat batter. It's not just how you handle the batter or dough to prevent gluten formation, many ingredients also do the job of interfering with its development. For example, butter and shortening coat the flour strands and prevent moisture from reaching them, while sugar acts as a tenderizer because it attracts water away from the proteins in the flour.
SARAH SAYS: Ingredients that tend to strengthen gluten are salt, milk, and acids (ex., vinegar, sour milk). Ones weaken it are fat, sugar, alkalis such as baking soda), and added starch such as, rice or potato starch.
Only wheat and related grains have the qualities necessary for the expansion of an initial dough or batter, wheat being more satisfactory. Although various flours are used in baking, some amount of wheat flour must be added if any significant degree of leavening is desired. Protein in the flour, known as gluten, combines with water or moisture to produce an elastic and porous web network capable of trapping gas bubbles released by the action of a leavening agent.
Sweet baking recipes such as layer cakes, biscuits, cookies, and muffins typically make use of chemical reactions rather than fermentation for leaven used in yeast breads. These recipes generally employ a flour (all-purpose or cake) containing less gluten than that used (bread flour) in yeast-leavened goods. Baking soda is most commonly used, but it must be properly combined with counteracting acids in order to release a sufficient amount of carbon dioxide. Such a combination is provided in baking powder, whose formula also serves to regulate the timing of the gas's release.