All-purpose flour is a pantry essential, but with a little tweaking, it can also serve as a substitute for cake flour, self-rising flour, and other specialty flours. While most home bakers rely on all-purpose flour for baking tender chocolate chip cookies and making Sunday morning pancakes, recipes that use cake flour and self-rising flour are less common. So unless you bake a lot, you might not have cake flour and self-rising flour ready in your pantry. Rather than run into town to pick up a bag at the last minute, you can substitute all-purpose flour (a.k.a. AP flour) for these varieties at home, using a few additional ingredients that you likely already have on hand. Yup, we just saved you a trip to the grocery store, all in the name of a moist, tender slice of chocolate cake (win-win).
Determining the protein content in flour
Before we talk about how to make a flour substitute, let’s get into the differences between these varieties of the pantry staple. Cake flour is a low-protein flour used for cake recipes (as well as some cupcakes and quick breads) that demand a fine crumb and delicate texture. Don’t confuse it with pastry flour, though, which is used to make pie crusts and tarts. Cake flour has a protein count of about 6% and pastry flour has a protein count of approximately 8%. In addition to having a lower protein level, these two types of flour contain less gluten than all-purpose flour—but bakers beware: They are not gluten-free nor are they a substitute for gluten-free flour. By comparison, all-purpose flour has a higher protein content, between 10% and 11%. FYI, bread flour has the highest protein content, around 13%.
So what is cake flour, actually?
Cake flour is typically made one of two ways: It’s either milled from a type of wheat that’s high in starch and has less protein than more common varieties, or it’s made from all-purpose flour that has some type of starch mixed in. The protein in any flour is what becomes glutenous when liquids are introduced. This is both a good and a bad thing because gluten content is what gives structure to your baked goods. However, introducing too much gluten can make your cake recipes come out tough and chewy.
In certain delicate recipes like chiffon or angel food cake, you want a soft, light texture with just enough structure—the low protein content of cake flour helps achieve this.
You can make a cake flour substitute by mixing a few tablespoons of cornstarch (or a cornstarch substitute, but more on that later) into all-purpose flour, which will help inhibit gluten formation. The result? A cake that's just as tender as it would be if you used store-bought cake flour.
How to make cake flour out of all-purpose flour
Instead of keeping a box of cake flour on hand for the occasional recipe that calls for it, you can make homemade cake flour. Here’s the formula: For every cup of cake flour called for in a recipe, use a measuring cup to scoop and level 1 cup of all-purpose flour (or whole wheat flour, if you want a nuttier flavor and slightly more nutritious bake). Next, remove 2 Tbsp. flour from that measurement (go ahead and add those two tablespoons back to the bag—you don’t need them). Add 2 Tbsp. cornstarch to the measured all-purpose flour. Whisk to combine and then sift the flour and cornstarch mixture—sifting is super important to ensure that the cornstarch is thoroughly combined with the flour and the mixture is light and airy. Use this substitute anytime a recipe calls for 1 cup cake flour, doubling or tripling as needed.
Let’s say you’re baking a recipe that calls for cake flour, and you’re ready to make a homemade flour substitute, but you realize you’re out of cornstarch too. If you don’t have cornstarch, you can use arrowroot powder or tapioca flour instead. These are sourced from different plants, but all three ingredients can act as a thickening agent and can be used to make DIY cake flour.
