All-Purpose Flour vs. Cake Flour: Differences and Substitutes

There are a growing number of specialist flours available today, from hearty bread flour to the fine Italian 00 flour used in pasta and pizzas. But when exactly should you be using these specialist flours, and when is it OK to fall back on an all-rounder? We take a look at the differences between specialist cake flour and all-purpose flour to find out.

What is the difference?

The main difference between all-purpose flour and cake flour is the gluten content. Gluten is what gives baked goods their structure, but if you use too much of it, it can make them tough. How much gluten you need depends on what you’re baking - a chewy, crusty loaf of bread requires a strong structure and plenty of gluten, while a light, fluffy cake should have less in order to preserve its delicate texture. 

Because all-purpose flour is designed to work for every type of bake, its gluten content is moderate, at around 10 to 13%. Cake flour, however, has one of the lowest gluten contents, at around 7 to 9%, which makes a much softer, lighter crumb. 

Another important difference is grain size. This affects the way flour behaves during baking because smaller grains absorb more water. All-purpose flour can vary in texture, but it's grains are usually of average size, making it suitable for a wide variety of bakes. Cake flour, on the other hand, is milled extra-fine, to keep your cakes deliciously moist.

When to use cake flour

You can use cake flour for any bake where you’re looking for a light, airy texture. Delicate cakes like chiffon cakes or angel food cakes will particularly benefit from using cake flour, but you can also use it to add a lighter touch to sponge cakes, cupcakes, muffins and scones. 

It isn’t only cakes that can be improved with cake flour. Some delicate pastries can also benefit from a lighter crumb, and it can even be used in certain cookie recipes. For example, shortbread is often made using cake flour to give it that trademark crumbly texture.

When to use all-purpose flour

As the name suggests, all-purpose flour can be used to make any type of bake, including bread, cookies, pastries, pizzas, cakes and muffins. It may not make the very best version of these things, however, because it tends to be a bit of a compromise between what is needed for many different recipes. There are specialist flours for many of these bakes too, including bread flour, pastry flour, or 00 flour for pizza.

That said, there are some bakes where all-purpose flour is pretty much perfect. Most cookies taste great made with all-purpose flour, as do pancakes and waffles. In fact, there are even some cakes that work better with all-purpose flour. Cakes that contain a lot of wet ingredients, such as fruit cake or banana bread, need a little more structure to hold everything together, and the extra gluten in all-purpose flour works perfectly.

How to convert all-purpose flour to cake flour

If you don’t have any cake flour, it’s actually pretty simple to make your own at home using all-purpose flour and cornstarch, an ultra-fine powder made from the starchy endosperm of dried corn kernels. Because cornstarch is gluten-free, you can essentially use it to ‘dilute’ the gluten content in the all-purpose flour, and its fine grain helps the mixture to absorb more moisture. This method is great in a pinch, and it’s also a smart way to avoid buying many different types of flour that you then need to use up.

To make 1 cup of your own cake flour, add 2 tablespoons of cornstarch to your measuring cup, and top it up with all-purpose flour, so you have a level cup. Whisk the mixture together and then sift, to make sure everything is thoroughly mixed together. 

What is self-raising flour?

Self-raising flour, is a mixture of all-purpose flour, baking powder and salt. Baking powder causes a chemical reaction inside your dough, creating hundreds of tiny air bubbles that cause the bake to rise. It is often added separately, so self-raising flour is essentially a time-saving product, containing two ingredients in one.

If your recipe calls for all-purpose flour and baking powder, you can simply swap for the same amount of self-raising flour and leave out the baking powder. On the other hand, if your recipe calls for self-raising flour and you only have all-purpose, you can make your own by mixing the all-purpose flour, baking powder and salt yourself. Again, this is a good way to streamline your larder, so you don’t have various different types of flour that all need using.

To make your own self-raising flour, mix 1 cup of all-purpose flour with 1 ½ teaspoons of baking powder and ¼ teaspoon of salt. Whisk the ingredients together and then sift them, to make sure everything is well mixed.

If you want to find out more about the different types of flour available, take a look at our article explaining the difference between bleached and unbleached flour.