When you choose a flour for baking, you are choosing how much gluten is going to form, and hence how much structure your baked good is going to have. All else being equal, the determining factor is how much gluten-forming protein the flour contains.
Conveniently, flour companies don’t just label their flours with a percentage of protein: They put the intended purpose right in the name of the flour. Here are four common types of flours and the differences among them.
What Is Bread Flour?
Bread flour is a high-gluten flour, meaning that protein comprises upwards of 12 percent of the weight of the dry flour. When bread flour is mixed with water and kneaded, much of that protein links together to form stretchy, strong strands of gluten throughout the dough. Gluten makes the dough stretch enough to be workable; holds onto the bubbles that form when the dough rises, giving it height; and produces a chewy bite when you eat it.
The main difference between bread flour and all-purpose flour is the protein content. With a protein percentage of at least 12, bread flour is the highest-protein flour available. All-purpose flour is more a workhorse because its protein content (between 9 and 12 percent) is high enough to provide structure to sandwich breads yet low enough to produce a tender crumb in many cakes.
What Is All-Purpose (AP) Flour?
All-purpose flour, fondly known as AP flour, contains on the order of 9 to 12 percent protein, right in the middle of the range for flour. It’s sturdy enough to turn into a handsome loaf, yet dainty enough to be cake instead. The results won’t be quite the same as using a specialized flour for those purposes, but it works! And AP excels at all the baked goods that you want to be neither too chewy nor too dainty: Mellow sandwich loaves, pancakes, muffins, breadings, cookies. And you can mix another flour with some AP flour if you want to moderate the former’s extreme tendencies.
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What Is Cake Flour?
Now we’re into the realm of soft flours, designed to produce a delicate result. Cake flour is 7 to 9 percent protein, so it forms little gluten, especially if the recipe combines the flour with fat before adding liquid, which limits gluten formation even further. Cake flour is typically milled finer than AP flour, in the name of tenderness. And, while AP and bread flours typically contain a small amount of malted barley or its enzymes, which help produce food for yeast, cake flour does not.
What Is Pastry Flour?
Pastry flour is substantially similar to cake flour, another big softie in the 7 to 9 percent protein range. Brands that sell both cake and pastry flour typically make one a percentage point or two higher than the other, and/or mill one finer, but the approach varies from brand to brand.
The common substitution shortcut of creating cake or pastry flour by cutting AP flour with a small amount of cornstarch—about 20 grams of cornstarch for every 100 grams of flour—works because the dilution simply reduces the net amount of protein in the flour. (Cornstarch does not contain protein.)
What Is Bleached Flour?
Wheat flour is naturally yellowish, because it contains a small amount of beta carotene. Bakers who desire a brilliant white baked good may prefer flour that has been bleached to whiten it. Peroxide bleach is used on all kinds of flour and doesn’t significantly change its baking properties. Chlorine bleach is sometimes used instead, specifically for cake and pastry flour. Unlike peroxide, it does change the chemistry of the starch and protein. A bleached cake flour is thus more able to absorb water and cling to fat, so it can be used to produce a loftier cake that remains very tender.
Tips for Substituting Flours
- There's no substitute for all-purpose flour. Keep this kitchen workhorse on hand.
- You can use all-purpose flour in place of other types of flour. It won't be exactly the same (breads and pizza crusts may bake up with slightly less chew) but it will be perfectly acceptable, especially if it's a baked good that you want to be neither too chewy nor too dainty.
- You can mix another flour with some all-purpose flour if you want to moderate the former’s extreme tendencies.
- To substitute for cake flour or pastry flour, use a combination of all-purpose flour cut with a small amount of cornstarch (about 20 grams of cornstarch for every 100 grams of flour).