How Does Flour Work?
When mixed with a liquid, flour forms a structure around the gasses produced by the leavening which causes the dough to rise. Then, as the starches in the flour are cooked, that framework becomes solid enough to hold everything in suspension. The exceptions are cheesecakes and sponge cakes, which are held in suspension by the protein cells in the eggs.
The type of flour you use will affect the texture, stability and overall outcome of your buns, cakes, pies and cookies. When the word "flour" is used by itself, it always refers to a product obtained through the milling of wheat exclusively. All other flours are preceded by the name of their source, such as rye flour, corn flour, barley flour, etc.
Wheat Flour
Cultivated wheat can be categorized into two types: hard and soft. This classification refers to the hardness of the wheat berry itself, and also the amount of gluten in the wheat berry. Generally, areas that receive less rainfall, such as the northwestern United States and western Canada, produce hard wheat that is very high in protein. The southern states get more rainfall, and produce soft wheat, which has less protein. Whether or not one type is “better” than the other depends entirely on what you are baking. For example, protein is essential in bread making, giving it that delightful chewy quality, but who wants chewy cakes?
The wheat berry is composed of essentially 3 parts: the bran, the germ and the endosperm.
- The bran is the hard outer shell that covers the berry and protects it from the elements. An excellent source of fiber, the bran also contains most of the minerals found in wheat. Because the bran has sharp edges, which cut through the gluten strands, it is removed during milling. You will have to add it separately to enjoy its benefits.
- The germ is the part of the grain that would become the plant, if cultivated. The germ, aside from its delicious flavor, is very high in protein and B vitamins. It is removed in the milling process because it causes the flour to become rancid more quickly, due to its high fat content.
- The endosperm is the food that the seed would consume to become a plant. The flour that we use for baking, unless it is whole wheat, has had the germ and the bran removed. The remaining endosperm is comprised mostly of starch and protein.
Gluten
If you've ever made bread, you know that you must develop the gluten in order to get a decent rise out of your loaf. But what is gluten? There are as many as 30 different types of protein in wheat, but 2 of them, glutenin and gliadin, when combined with water, form the elastic substance known as gluten. Gluten becomes elastic and stretches around the gas bubbles produced by the yeast in bread, thereby causing the dough to rise. Wheat is the only grain that has these gluten producing proteins. For this reason, breads made with other grains; such as rye, corn or oats must be fortified with wheat gluten if you expect them to rise.
Additives
In order to perform optimally, flour must be aged after milling. The miller will sometimes speed up the aging through a chemical process. In addition, the FDA has mandated that milled grains be fortified with nutrients that are lost in the milling process. These include thiamin, niacin, riboflavin and iron. Folic acid, another member of the B family, has been added to the list as a prevention against birth defects.
Anything Else?
Malted barley is added to all-purpose and bread flour to improve flavor and to enhance the enzyme activity that converts starch into sugars. Some folks like to have their whites their whitest, so along came bleached flour. Bleached flour has been whitened with chlorine or peroxide (which evaporate out) or naturally through the aging process. Ascorbic acid (vitamin C) is commonly used to oxidize and preserve flour instead of potassium bromate.
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