Cake flour; Do We Need it and Why? An Explanation of Gluten and the Effects Thereof, and Other Factors in the Specialness and Particularity of Flour…
It seems like a silly way to make you buy more stuff, but there are a few real differences between cake flour, standard flour, and bread flour, and they can make a real difference in how your baked goods come out.
The first issue is GLUTEN. Cake flour has a much lower protein content than regular flour. Bread flour has more. Yes, Virginia, there is protein in flour. It is called gluten. (I know about this more than most because one of my nearest and dearest suffer from Celiac Disease, where he suffers greatly from ingesting any of this said gluten, but that is another story. Anyone interested in financing my gluten free restaurant, please contact me.) Gluten is very good for bread, as it creates a stretchy dough. You want bread to have some bite and heft. But cake should be light and fluffy, not chewy. So, cake flour = less gluten, bread = more gluten.
Cake flour is also milled from specific types of wheat that have lower protein contents, extra finely, and often bleached more, the result causing the protein in the flour to break down even further. This causes cake flour to be better than other flours at two important things – making sure that that it holds large amounts of fat and sugar, while still remaining fluffy and light.
Bread flour, on the other hand, is made from wheat known to have higher gluten content, and will have small amounts of malted barley flour and vitamin c or potassium bromate added. These additives help yeast develop and fulfill it’s self-actualization, and also function to make the existing gluten extra stretchy and retain gas from the yeast as the bread rises and bakes.
INTERCHANGEABLE?
Maybe, but maybe not. Use bread flour or all purpose flour for bread, don’t use cake flour.
Use cake flour or all purpose flour for cakes, don’t use bread flour. If a recipe calls for one cup of cake flour, you can sub ¾ cup sifted bleached all purpose flour and two tablespoons of cornstarch.

