The function of flour in cooking or baking is to provide structure and texture through the formation of gluten. Flour is an important ingredient in breads, pastries and pasta and is used to thicken soups and sauces.
Although flour can be milled from a variety of grains, it is most typically composed of wheat. When water is added, it hydrates the proteins and binds to form gluten. Gluten, when combined with heat and moisture, provides elasticity and strength to baked goods. Flour is what binds ingredients to form dough or batter. The protein in flour creates volume and texture while the starches sustain form after the product is removed from heat.
Not only does the starch found in flour aid in rising, it absorbs moisture when combined with heat over 140 degrees. This process, called gelatinization, sets the finished product during baking. The protein percentage of the flour affects the strength of the dough. Bread and pasta require high-gluten flour for strong, sturdy structure and chewy texture. The delicate texture of cakes and pastries is due to a flour with a lower protein percentage, such as pastry or all-purpose flour. Flour can be used as a thickening agent in sauces, soups, stews and gravies.