Flour provides the structure for baked products, from breads to the most delicate cakes. The main difference between flours is their protein content. Hard flours, with a higher protein content, are used in breads to give them a dense, chewy texture. Flours made from soft wheat, with the least protein, are used in cakes, pastries, cookies, crackers and noodles. All-purpose flour is a combination of both hard and soft wheat and, as the name suggests, you can use it for most purposes, from bread to cake.
White Flour
White flour is the ground endosperm, or starchy part, of the wheat kernel. Both the wheat germ -- which is the seed -- and the bran -- the outer shell of the wheat kernel -- have been removed in processing. Whole wheat flour contains the endosperm and bran; 100 percent whole wheat flour contains the endosperm, bran and wheat germ. Cake and pastry flours are usually white flour without the bran and wheat germ.
Cake Flour
Cake flour is a very fine flour made from soft wheat, and it has about 7 or 8 percent protein. It has more starch and less protein than other wheat flours, so it makes a more delicate and tender cake than all-purpose flour would. Protein produces gluten, which is desirable for breads because it creates a tougher structure necessary for the bread to rise. However, gluten makes cakes tough and dense, so a low-protein flour is more desirable. Cake flour produces cakes with higher volume than all-purpose flour would.
Pastry Flour
Pastry flour is a soft white flour, with a texture between all-purpose and cake flour and about 8 or 9 percent protein.. It has slightly more protein than cake flour, but less protein than all-purpose flour. Pastry flour is meant for making pie crust and biscuits, which need more structure than cake flour would give. Because it has less protein than all-purpose flour, pastry flour makes a more tender product and is less likely to become tough due to over-mixing as all-purpose flour would do. You can substitute pastry flour for cake flour.
Substitutions
Because cake flour is bleached, it is slightly more acidic than unbleached flour. This makes it work well in recipes that have a higher ratio of sugar to flour, such as cakes. Pastry flour can be bleached or unbleached but still works well in cake recipes. While it is all right to substitute pastry flour for cake flour, don't use all-purpose flour in cake recipes that specifically call for cake flour. If you run out of cake flour or pastry flour, and have to use all-purpose flour, remove 2 tbsp. of flour for each cup called for in your recipe.
References
- Virginia Polytechnic Institute; From Our Fields to Your Table?; Wendy Rohrer
- What's Cooking America: Flour - Types of Flour
- The Kitchn; What's the Difference? Cake Flour, Pastry Flour, All-Purpose Flour, and Bread Flour; Emma Christensen; January 2009
- Cooperative Extension Service; University of Kentucky; Pies and Cobblers; Sandra Bastin
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