In the world of bread, wheat flour dominates. Rye, the next most popular bread flour, doesn’t even come close. Part of the issue is that rye flour behaves differently than wheat flour, and it can be more difficult to make a lofty loaf of bread with rye. That’s what we thought, anyway, until we began looking into rye more closely (see how American rye and European rye are different from one another). Here, we’ll walk you through some of the differences between rye and wheat flour and help you understand how to get the most out of your rye.

Why Rye Is Different from Wheat

Rye and wheat are both grains, and they’re so closely related that they can form a hybrid, which is called triticale. Flours made from both wheat and rye have some similarities in terms of their bran-germ-endosperm makeup. Rye flour also contains water, just like wheat, as well as proteins, starches, and enzymes. But the way these components work is different in rye and wheat.

Protein

Like wheat, rye contains proteins that are not suitable for people with celiac disease. But rye’s proteins, called secalins, are different from wheat’s proteins (glutenin and gliadin) in significant ways. In fact, in terms of making bread, rye’s proteins are irrelevant. Whereas wheat’s gluten proteins form a webbing that helps bread rise and hold its structure, rye’s proteins don’t form this kind of structure.

That’s why rye is often thought of as inferior to wheat for making bread. Rye is frequently mixed with wheat to make what we call rye-flavored bread. That is, it has a crumb structure built from wheat, but with a touch of rye flour for flavor.

Pentosans and Polysaccharides

Ever wonder why making dough from rye flour requires more water than wheat flour–based doughs? It’s because of its polysaccharides. Simple sugars, called monosaccharides, are the most basic forms of carbohydrates. When those sugar molecules are bound together in long chains, they’re called polysaccharides. The amylose and amylopectin found in starch granules are polysaccharides.

The two main non-starch polysaccharides in rye are pentosans and beta-glucans (β-glucans), and together they bond up to one-third of the water in dough. The more water-binding polysaccharides a flour contains, the more water the dough will need. Rye flour contains higher levels of pentosans and β-glucans than wheat, varying from 6% to 12%. This gives rye better water-binding abilities than wheat flour, and it’s why rye dough needs more water than wheat dough. In other words, rye is a thirsty ingredient.

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.

Pentosans also play a big role in rye’s structure-forming properties. When the dough is baked, pentosans cling to the water they absorbed. They then thicken to form a mucilaginous liquid, which is how rye bread gets its structure. 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 ways of making bread—pentosans versus gluten—and the mechanisms couldn’t be more different.

Particle Size

When you’re making bread with wheat flour, particle size isn’t generally an issue. But with rye, its ability to make a good dough strongly depends on particle size. We love a good dense rye bread, but we also can’t get enough of the light, voluminous ryes that you find in northern Europe. The secret to making a flavorful and less dense 100% rye bread is using finely ground flour—really finely ground (see our method, in Modernist Bread vol. 2:226). It’s a secret we learned after a number of tests with rye flours from Europe, where rye flour is much different from that produced in the United States (see our blog to learn more). Here, your best bet is to start with the lightest rye you can find and then sift it to make it even finer.

Understanding Different Rye Flours

In North America, rye flour isn’t regulated, but there are some rules of thumb. Generally, how the grains are sifted roughly correlates to how much bran and germ are in the flour. The less bran and germ, the lighter the flour, so color can be a visual cue for the rye. There is a notable difference between American rye and European rye, which we explore in detail in our blog: The Difference Between American Rye and European Rye.

Type of Flour Composition

• WHITE OR LIGHT RYE FLOUR: germ and bran are removed; milled from the endosperm
• MEDIUM RYE FLOUR: similar to light rye flour, but with more of the bran included; more rye flavor than white or light rye
• DARK RYE FLOUR: includes all parts of the rye kernel; some millers use 100% of the whole grain; others use smaller proportions of the GERM AND BRAN; still others use the leftovers from sifting white, light, or medium rye flour and label it as “dark rye”
• RYE MEAL: whole grain milled in proportions of the harvested berry; sometimes labeled “whole-grain rye flour”; can be ground fine, medium, or coarse
• PUMPERNICKEL FLOUR OR MEAL: coarse-ground whole-grain rye flour; also the name of a traditional German bread

Rye breads have a longer shelf life than bread made with wheat flour because rye stales at a slower rate than wheat; that’s because of differences in starch, protein, water absorption, pH, and other factors.

Rye flour contains many nutrients for yeasts and enough microorganisms to get the fermentation process going quickly. This explains why a levain made with rye is the easiest to make—and also why breads made with rye levain and rye flour move fastest during fermentation.

Want to learn more about the science behind common bread ingredients? We have an entire email course that addresses how ingredients like flour, salt, water, and more affect the bread-making process. Learn more at the Modernist Bread School.