Flour is probably one of the first ingredients that comes to mind when you consider making bread. Flour is the core matter of bread and provides the main structure that anchors the other ingredients in the baked loaf in part because its largest component is starch.
From a bread-making perspective, there are two main types of flour that contribute to a bread’s structure: wheat flour and rye flour. However, we will still cover other flour types, including gluten-free alternatives, in this post.
WHEAT FLOUR
The term “flour” is generically used for wheat flours, which contain two important gluten-forming proteins, glutenin and gliadin, that combine to form an elastic network of gluten when hydrated, trapping gas bubbles and allowing for an airy crumb.
Changing the amount of flour in a bread recipe warrants considerable focus because wheat flours vary in bran, germ, and protein content, which likewise affect the composition of the dough and characteristics of the baked loaf.
HOW IT WORKS
- When the gliadin and glutenin proteins come into contact with water in a process known as hydration, they organize into strands called gluten.
- As the flour becomes fully hydrated, these strands combine with one another to create an elastic webbing throughout the dough that is key to the final structure of the baked bread.
- Also, as the dough is mixed together, millions of tiny bubbles are formed (for more on this, see page 59 of Modernist Bread at Home and Modernist Bread vol. 2:32). These bubbles will later inflate like balloons; it is the presence and the elastic nature of the gluten network that allow this expansion to occur.
Another important component of flour is starch. When it combines with water, enzymes break some of it down into simple sugars; these sugars fuel the yeast activity that makes bread rise and aids in the browning of the crust. Additionally, when the dough is heated, the starch gelatinizes, which contributes to the structure of the crumb. See our latest blog post for more details.
Wheat flour contains gliadin and glutenin, but not every type of flour does, and those that do can contain them in varying percentages. Flours well suited to bread making are referred to as “strong” flours and may be marketed as bread flour and/or high-protein flour.
As a general rule, flours with a higher protein content absorb more water than those with a lower protein content. Bread flour typically contains a protein content between 11.5% and 13%. If you substitute an all-purpose flour with 10% protein, your baked loaf will likely have a tighter crumb. Wheat flours with a low protein content are not generally intended for breads.
The kind of flour used in bread making can have an impact on crumb; typically, breads made with a greater percentage or entirely of whole wheat flour or rye flour have a denser crumb (for a more detailed discussion on each, see pages 165 and 282 of Modernist Bread at Home or Modernist Bread vol. 2:13). Bread made with coarse-ground 100% rye flour does not form an elastic network and tends to be dense; using finely ground rye flour can produce a 100% rye bread that is less dense (see our blog post for more).
Want more details on the different classifications of wheat flour? Click here for more information on our blog.
RYE FLOUR
Rye works a little differently. Rather than relying on gluten, rye flour forms networks through starches and pentosans (large, complex sugar molecules). Rye flour differs from wheat flour in that rye contains a ratio of glutenin to gliadin that prevents it from producing enough gluten to form an elastic dough like wheat flour does.
HOW IT WORKS
- Rye flour contains higher levels of pentosans than wheat. This gives rye better water-binding abilities than wheat flour, and it’s why rye dough needs more water than wheat dough.
- When pentosans mix with water, they form a viscous solution that traps carbon dioxide. In fact, rye’s pentosans can absorb up to 16 times their weight in water, which is why rye doughs are notoriously sticky and slack.
- The carbon dioxide that’s produced by the yeasts and trapped inside this viscous liquid is what ultimately determines the consistency of the crumb. Interestingly, pentosans delay starch retrogradation, which is why rye bread can stay moist for days and sometimes weeks.
We find it fascinating that for all the grains humans grow, there are two key factors in making bread—pentosans versus gluten—and the mechanisms couldn’t be more different.
OTHER FLOURS
Of course, you can grind almost any grain into flour, but the problem is, most other grains don’t have a means to create structure as dough proofs, which allows gas bubbles to expand. Wheat and rye contain the elements that make this possible.
All starches, including those in non-wheat or non-rye flours, do a good job of providing additional structure once the dough heats up in the oven, as rigid walls form to support the crumb. That’s because starches gelatinize with heat plus hydration, and once that gel forms, it helps to prevent the loaf from collapsing.
What all this means is you can’t substitute another flour for wheat flour in a recipe and expect to get the same results. Flours made from grains other than wheat and rye can play great supporting roles in your bread-baking repertoire (they can add a lot of interesting flavor and texture to bread). You won’t typically be using any of these other flours on their own. Instead, they’re often used in conjunction with wheat flour and/or other ingredients.
There’s a fairly simple rule: when you’re making bread with wheat flour, you may add up to 30% of these other flours (except soy) and still get a decent loaf. Any more than that will hurt the crumb. If you’re not starting with a base of wheat flour, you’ll need something else, such as xanthan gum or vital wheat gluten (see page 338 of Modernist Bread or Modernist Bread at Home, page 345), to help turn other flours into risen loaves of bread.
GLUTEN-FREE OPTIONS
Another reason to explore other flours is for special diets and gluten-free baking. Many companies have developed commercial gluten-free flours that can be substituted 1:1 for all-purpose flour. These mixes work well, though generally not as well as wheat flour would. While these premade mixes are convenient and can be used in some of our recipes, we prefer our own Gluten-Free Flour Blend on page 351 of Modernist Bread at Home and Modernist Bread vol. 5:284.
Our gluten-free flour blend combines white rice flour, brown rice flour, cornstarch, tapioca starch, and glutinous rice flour. (Don’t be put off by the word “glutinous” because the flour doesn’t contain any gluten—in the case of rice and rice flour, “glutinous” simply refers to the stickiness of the rice.) Of these ingredients, the glutinous rice flour played a major role in our baking success: when hydrated in doughs and then baked, it retains a particular chewiness reminiscent of gluten. Its flavor is too strong to make an appetizing loaf all on its own, but it does contribute a great deal when mixed with other flours.
Further Reading
- Modernist Bread vol. 2—Chapter 8: Flour
- Choosing the Right Wheat Flour for the Job
- Gluten-free flour recipe—Modernist Bread at Home, page 351 / Modernist Bread vol. 5:284
- How Rye Works
- The Sad Tale of American Rye
- Bread Is Lighter than Whipped Cream
- Gluten—How does it work?