When referring to flour, most people mean wheat flour, unless they say otherwise. Flours made from other foods include amaranth, barley, buckwheat, millet, oats, soy, quinoa, rice, rye, and triticale.
Wheat flours are classified by the amount of protein they contain. Wheat flours made from soft wheats are relatively low in protein and generally are used for making cakes, cookies, pastries, and crackers. Those flours made from hard wheats are high in protein and generally are used for quick and yeast breads.
All-purpose flour: This flour is made from a blend of soft and hard wheat, or medium-protein wheats. As its name implies, it is used as a multipurpose flour in a range of baked goods.
However, different manufacturers use varying proportions of hard and soft wheats, so the protein level in all-purpose flours ranges from 9 to 15 grams per cup. When baking yeast breads, use an all-purpose flour or a bread flour with at least 2 3/4 grams of protein per 1/4 cup because high-protein flours tend to produce finer textured, higher-volume yeast breads. To find out how much protein an all-purpose flour contains, check the amount of protein in grams per cup on the flour bag's nutrition label.
Cake flour: A soft wheat blend. Its low protein and low gluten content make it suitable for baking fine-textured cakes. Cake flour produces a tender, delicate crumb because the gluten is less elastic. Many bakers use it for angel food and chiffon cakes.
Self-rising flour: Self-rising flour is an all-purpose flour that contains baking powder, baking soda, and salt.
Bread flour: Bread flour contains more gluten and protein than all-purpose flour, making it ideal for baking breads. When rubbed between your fingers, it feels a bit more granular than all-purpose flour. When used instead of all-purpose flour, you usually need less. If you use a bread machine, use bread flour instead of all-purpose flour for the best results. Or, use all-purpose flour and add 1 or 2 tablespoons of gluten flour (available at grocery or natural food stores).
Instant flour: A patented process is used to produce a quick-mixing flour for use in thickening gravies and sauces.
Whole wheat flour: Whole wheat or graham flours are processed less than plain flour and, therefore, retain more of their nutrients and fiber. Whole wheat flour, also called graham flour, is a coarse-textured flour ground from the entire wheat kernel. It is good in breads and some cookies, but generally is not the best choice for pastry or other delicate baked goods.
Other Types of Flour
Specialty flours: Specialty flours, such as whole wheat or graham, rye, oat, buckwheat, and soy, generally are combined with all-purpose flour in baked products because none has sufficient gluten to provide the right amount of elasticity on its own.
Rye flour: Rye flour is a traditional ingredient in many breads, cakes, and pastries of Northern and Eastern Europe. The gluten in rye flour adds stickiness to the dough but lacks the elasticity of wheat flour gluten. Using a large proportion of rye flour to wheat flour results in a more compact product.
Oat flour: Oat flour can be purchased or made by grinding rolled oats to a fine powder in a food processor, 1/2 cup at a time.
Soy flour: Soy flour is a cream-colored, strong-flavored flour that is a rich source of protein and iron and contains no gluten. Baked products made with soy flour brown more quickly, so you may have to reduce the baking temperature depending on the amount used.