What's the difference between Medium Rye Flour and Dark Rye Flour (Pumpernickel)?

Medium Rye Flour: 9.00-10.50% protein, absorption 1.080×, hydration 80-95%. Dark Rye Flour (Pumpernickel): 8.00-9.00% protein, absorption 1.100×, hydration 90-110%.

Can I substitute Medium Rye Flour for Dark Rye Flour (Pumpernickel) 1:1?

Yes — absorption is close enough that a 1:1 swap works with minor tweaks.

Which is better for open-crumb sourdough?

Dark Rye Flour (Pumpernickel) supports higher hydration (up to 110%), making it better suited to open-crumb hearth loaves than Medium Rye Flour (max 95%).

Side-by-side comparison

Medium Rye Flour vs Dark Rye Flour (Pumpernickel)

	Medium Rye Flour	Dark Rye Flour (Pumpernickel)
Protein	9.00–10.50%	8.00–9.00%
Absorption (× bread flour)	1.080	1.100
Hydration range	80–95%	90–110%
Category	rye	rye
Ash %	1.50	2.00

Medium Rye Flour

Medium rye contains most of the rye grain with moderate bran content. Rye proteins do not form gluten like wheat proteins — instead, rye structure comes from pentosans (soluble fiber) that absorb 8-10x their weight in water. This means rye dough is sticky, paste-like, and requires different handling than wheat. Hamelman's reference specs target 80-95% hydration for rye-dominant doughs. Central Milling's Organic Medium Rye is the US reference. At 20-40% in a blend with bread flour, medium rye adds color, flavor complexity (tangy, earthy), and extends keeping quality. At 100%, expect dense crumb and strong sour flavor.

Dark Rye Flour (Pumpernickel)

Dark rye (pumpernickel flour) is coarser, contains more bran, and has the deepest flavor of all rye flours. Absorption is 10% higher than bread flour baseline. Ash content 2.0%+ indicates high mineral content from extensive bran inclusion. Used in traditional German pumpernickel (100% dark rye, 24+ hour steam bake) and Scandinavian rye breads. Hamelman's pumpernickel formula targets 95-100% hydration with 100% dark rye. Can also be used as 10-20% of a wheat-rye blend for strong rye character without going fully rye. Central Milling, Bob's Red Mill, and Janie's Mill are US reference sources.

Substitution math

When substituting Medium Rye Flour for Dark Rye Flour (Pumpernickel) in a recipe, absorption is close enough that a direct swap works. Expect minor texture differences but similar handling.