All-purpose flour doesn’t make good bread. And bread flour isn’t always a good choice for other baked goods. Here’s why.
Baking is the most scientific cooking method of them all. If you use the right ingredients and follow the steps and proportions of the recipe, you get a delicious result. If you go astray, the result will be anything but what’s described by the cookbook author.
I guess this is why ingredient substitution is a touchy subject in the baking world. With few ingredients and a thin margin for error in every recipe, you need to know the ingredients you’re using inside and out, and you can’t always afford to use one instead of the other.
Still, ingredient swaps are possible, as long as you know how to do them. So let’s talk about two of the most common types of flour in baking—all-purpose flour and bread flour—to understand how they’re similar, how they differ, and just how interchangeable they are.
What Is All-Purpose Flour?
All-purpose flour is the most common type of flour in the supermarket, and what most home cooks have in their pantry. As its name suggests, it’s a general use flour intended for breads, biscuits, cakes, focaccia and pizza doughs, and all kinds of other baked goods.
(Note: In many parts of the world, all-purpose flour is also known as “plain flour.” The two terms can be used interchangeably; they refer to one and the same thing.)
All-purpose flour is made from a mixture of soft and hard wheat. Its protein content can vary from region to region and state to state:
In the Southern US, Pacific Northwest, and Canada, all-purpose flour contains anywhere from 7.5 to 9.5% gluten. In the rest of the US, all-purpose flour has 11 to 12% gluten. In Europe, the protein content of all-purpose flour is about 10%, though every country has its own traditions and classification system.
Look for all-purpose flour in your local grocery store, and you’re likely to come across two varieties: unbleached and bleached.
Unbleached flour has aged naturally after milling. Bleached flour has been treated with chemicals, called bleaching agents, to accelerate the aging process. (The bleaching agents are usually benzoyl peroxide and chlorine gas.)
Bleached flour is white, fine, and powdery. Unbleached flour is straw yellow, dense, and somewhat grainy.
In most recipes, you can use bleached and unbleached flours interchangeably. Of course, there are differences: Doughs with bleached flour are slightly easier to work with because they form stronger gluten bonds during kneading. Baked goods with unbleached flour have a more artisanal texture and taste.
What Is Bread Flour?
Bread flour is a high-protein flour prepared from hard wheat. It has a gluten content of 12-15%, higher than other types of flour, which makes the baked goods prepared with it more elastic, stretchy, and chewy.
The high gluten content gives bread dough its distinctive structure and allows it to trap air bubbles better than goods made from other doughs. In other words, loaves of bread prepared with this type of flour come out airier and fluffier.
One of the reasons why professional bakers swear by bread flour is because its protein content makes it stronger and more stable than other flours, so it’s more suitable for mixing in a commercial mixer (rather than by hand or in a countertop mixer).
All-Purpose vs. Bread Flour
All-purpose flour and bread flour are refined wheat flours for baking. One is made from a mixture of soft and hard wheat, and the other of hard wheat only.
Both of these types of flour have had the hard outer layer of the wheat grain, called the bran, and the inner reproductive part, called the germ, removed. Having lost most of their fiber content, they are almost all protein and starch.
Bread flour contains slightly more protein than all-purpose flour, so it yields airier and chewier baked goods (think, for example, of a French baguette or an American hoagie roll). It also absorbs more water and requires a longer mixing time.
Substituting One for the Other
As a dough flour: When baking, you can substitute all-purpose flour for bread flour in a 1:1 ratio, and vice versa. For every cup of bread flour the recipe calls for, use one cup of all-purpose flour, or the other way round.
As a thickening agent: All-purpose and bread flour can be used interchangeably as thickeners in cooking, like when preparing béchamel sauce or a roux.