Science of Baking: My recipe calls for cake flour; can I substitute it with all-purpose flour?

Science of Baking - cake flour

Welcome to this new section of Sugar for the Brain!

Science of Baking (I like to call it the nerdy corner) will be all about the science behind what we bake. I love science! I think you do too because I’ve had a lot of positive answers when I proposed to do this section on Facebook (a long time ago!). I hope I’ll be able to do real experiments, like the post I did with the cake pops that crack, to show you what is really happening when you add high-protein flour instead of low-protein or if you don’t beat the egg whites enough.

I don’t have a degree in baking so I’m using the knowledge of great books and sources that you’ll find below each post.

Feel free to ask your questions! I’ll gladly do a Science of Baking post to answer it!

Science of Baking - cake flour


My recipe calls for cake flour; can I substitute it with all-purpose flour?

Nah, not really.

(And here come the scientific part, if you want a very simple explanation, jump to “In a few words” below)

The difference between cake flour and all-purpose flour (and between all kinds of flour for that matter) lies in the amount of protein (gluten). Gluten is a protein composite formed with two other protein: glutenin and gliadine. When you add liquid to flour, the two proteins bind together (in a web-like network way) to form gluten. Gluten contributes to the structure of your cake (holding it together) and its elasticity.

Cake flour has less protein than all-purpose flour which in turn has less protein than bread flour. Because it has less protein, Cake flour will produce less gluten than all-purpose flour. This will result in a more tender cake. For example, a lot of gluten will lead to a baguette-like texture.

Not only can you choose a low protein flour to reduce the amount of gluten formed in your cake, but there is also other ways to inhibit the formation of gluten (fat, alkaline and acid ingredients, etc). This will be the subject of the next Science of Baking.

Substitutions
Even if I do a lot of cakes, I never bought cake flour. I’ve always used substitutes with great results. The goal of these recipes is to lower the amount of gluten by substituting a little amount of all-purpose flour by cornstarch, which has no gluten. I’ve tried many recipes, here is a few:
http://low-cholesterol.food.com/recipe/cake-flour-substitute-87689
http://joythebaker.com/2009/09/how-to-make-cake-flour/
http://frugalliving.about.com/od/makeyourowningredients/r/Cake_Flour_Sub.htm

In a few words
If you use all-purpose flour instead of cake flour, you’ll get a cake that is less tender and fluffy. This is because cake flour has less gluten than all-purpose flour and less gluten makes more tender cakes.

Sources
Blais, Christina; Larrivée, Ricardo (2007). La chimie des desserts, Les Éditions La Presse.

Chattman, Lauren (2009). The baking answer book, Storey publishing.

Potter, Jeff (2010). Cooking for Geeks, O’Reilly.