Flour Types for Sourdough: Bread Flour, AP, Whole Wheat, and Beyond

When I started baking sourdough, I used whatever flour was on sale at the grocery store. All-purpose, bread flour, the bag with the nicest packaging — it did not matter to me because I did not know it mattered. It took about ten loaves before I realized that flour is the single most important ingredient in bread (which sounds obvious in hindsight, since bread is mostly flour). The type of flour you use affects hydration, gluten development, flavor, crumb structure, and crust quality. Choosing the right flour for your goals makes everything easier.

Understanding Protein Content

The most important number on a flour bag is the protein percentage. Protein forms gluten when hydrated, and gluten is the structural network that traps gas and gives bread its shape and texture. More protein means more gluten potential, which generally means a stronger, chewier bread that can handle higher hydration.

Bread Flour (12-14% Protein)

This is my default flour for sourdough and the one I recommend for most bakers. Bread flour has enough protein to build a strong gluten network that supports good oven spring, holds shape during proofing, and produces a satisfying chewy texture. It absorbs water well, which means it can handle the 70-75% hydration range that produces great artisan bread without becoming unmanageably sticky.

King Arthur bread flour (12.7% protein) is my everyday choice. It is consistent batch to batch, widely available, and performs reliably. If you can only buy one type of flour for sourdough, buy bread flour.

All-Purpose Flour (10-12% Protein)

All-purpose flour works for sourdough, and millions of great loaves have been made with it. The lower protein content produces a softer, more tender crumb compared to bread flour. The trade-off is less structural strength. AP flour doughs spread more during proofing, have less oven spring, and struggle at higher hydrations.

If you use all-purpose flour, reduce your hydration by about 5% from any bread flour recipe. A recipe calling for 75% hydration with bread flour should be tried at 70% with all-purpose. This compensates for the lower water absorption and weaker gluten network. AP flour makes an excellent sandwich bread where a softer crumb is desirable.

Whole Wheat Flour (13-14% Protein)

Whole wheat flour has high protein on paper, but it behaves very differently from white flour. The bran and germ particles act like tiny knives, cutting through gluten strands as they develop. This means whole wheat doughs need more water (the bran absorbs a lot), more time for gluten development, and gentler handling.

I covered this extensively in my whole wheat sourdough guide, but the short version is: do not substitute whole wheat 1:1 in a white flour recipe. Start with 20-30% whole wheat blended with bread flour, increase hydration by 5-10%, and extend your autolyse to at least 45 minutes to let the bran fully hydrate.

Rye Flour

Rye is a completely different animal. It contains proteins, but they do not form gluten the way wheat proteins do. Instead, rye relies on pentosans (complex sugars) to provide structure. This means rye doughs are sticky, dense, and do not develop the elastic, stretchy quality of wheat doughs.

For sourdough, rye is best used as a supplemental flour (10-30% of the total) blended with bread flour. It adds a distinctive earthy, slightly sweet flavor, deeper color, and a moist crumb. My rye sourdough bread uses 30% rye with 70% bread flour, which is a good starting point. Pure 100% rye bread is a separate tradition (German Vollkornbrot style) that requires completely different techniques.

Spelt Flour

Spelt is an ancient grain that is closely related to modern wheat. It has good protein content (12-15%) but the gluten it forms is more fragile and extensible than wheat gluten. Spelt doughs stretch easily but tear if handled roughly. They also ferment faster than wheat doughs because the simpler starch structure breaks down more quickly.

I love spelt sourdough for its nutty, slightly sweet flavor. Use 50-100% spelt with reduced hydration (65-68%), minimal mixing, gentle folding, and watch the fermentation carefully because it moves fast. Over-fermented spelt dough is nearly impossible to rescue.

Specialty and Ancient Grains

Einkorn, emmer, and Kamut are ancient wheat varieties gaining popularity among artisan bakers. Each has unique characteristics: einkorn is very low in gluten with a buttery flavor, emmer has moderate gluten with an earthy taste, and Kamut has good protein with a sweet, buttery quality. All of these require adjusted hydration and handling compared to modern wheat.

My recommendation is to experiment with these as 10-20% additions to your bread flour base before attempting 100% ancient grain loaves. This lets you experience their flavors and textures without committing to the significant technique adjustments they require.

A Note on Buying Flour

Freshness matters. Flour degrades over time, especially whole grain flours where the oils in the bran can go rancid. Buy from stores with high turnover, check milling dates if available, and store whole grain flours in the freezer if you do not use them within a few weeks. White flour keeps well in a cool, dry pantry for months.

If you have a local mill or can order freshly milled flour online, try it at least once. The difference between grocery store flour and freshly milled flour is similar to the difference between supermarket tomatoes and vine-ripened ones from a garden. It is not a subtle difference. Fresh flour produces bread with more aroma, more complexity, and a depth of flavor that reminds you bread is supposed to taste like grain, not just like nothing.