How Thickening Works

• Starch serves as the main ingredient for all thickening processes except for reduction, a method that causes the water to evaporate in a sauce. Starch thickens sauces, soups, stews and gravies by turning into a gel when cooked. Properly prepared, agents with lots of starch, such as all-purpose flour or cornstarch, have a neutral taste that blends into the foods they thicken.

Packed with Protein

• Both soy flour and bread flour are created to enhance the amount of protein, rather than starch, in each. Bread flour in particular is made to improve the elasticity of gluten in yeast breads. Bread flour typically is from 12 to 15 percent protein, which gives bread a strong structure and chewy texture. Soy flour is even more protein-packed, but its protein can't make gluten. Full-fat soy flour is 40 percent protein, while defatted soy flour has a whopping 55 percent protein. When it comes to thickening, both flours are less desirable because of the ways they affect both the taste and consistency of sauces.

Bread Flour Thickener

• You may use bread flour thicken any food that would normally call for all-purpose flour. Because of its extra protein, however, bread flour can give sauces a gooey texture, so watch it carefully to avoid overcooking. To thicken a sauce with bread flour, mix equal parts of flour and fat to create what's known as a roux. Butter is the first choice for making roux, but you may use shortening, oil or meat drippings as well. A white roux is cooked until the taste of flour has disappeared, while a brown roux is cooked until it turns brown and tastes nutty. Once the roux has reached the desired color and flavor, add it to the sauce and cook until it reaches the desired thickness.

Soy Flour Thickener

• Soy flour can have a strong "beany" taste when compared to a wheat flour, including bread flour. Experiment with using soy flour as a thickener to determine how it affects a sauce or gravy. In general, soy flour enhances gravies and cream soups more effectively than more transparent mixtures such as sauces and pie fillings. To thicken a sauce with soy flour, use it to replace all-purpose flour on a one-to-one ratio. Then combine it with a fat such as butter to create a roux. Cook the roux until it has reached the desired color, white or brown. Add it to the sauce and cook until it reaches the desired thickness.