Cake flour is an entirely different ingredient than the all-purpose flour we use to make things like sandwich bread and even most cookies. For starters, it has a lower protein content of around 7% to 8%, as compared to the 10% to 12% found in most all-purpose flour. Cake flour is also ground much more finely than other flours, giving it a soft and silky feel.
The lower protein and the finer grind both have a direct effect on the texture of cakes and pastries. The lower protein means that the flour forms less gluten as you work with it, which in turn keeps baked goods light and airy. The fine grind of the flour translates into pastries with a softer crumb. Some cake flours are also bleached to help cake set more quickly and also give them a lighter color.
Cake flour is the difference between a tall cake with a delicate crumb and one that is dense and somewhat coarse. If you're baking for a special occasion, it's worth it to use the right flour. Cake flour can also be used in cookies, bars, and other baked goods whenever you'd like a lighter or softer texture.
If you find yourself out of cake flour just when you need it, you can approximate it by adding two tablespoons of cornstarch to every cup of all-purpose flour. It's not quite the same, but the cornstarch will help soften the gluten and give you a finer crumb.
What brand of cake flour do you use?
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