Bread flour is the most reliable choice for sourdough, but all-purpose flour works too

Bread flour gives you the strongest, most open crumb because it has 12 to 14 percent protein — enough gluten to trap gas bubbles without overworking the dough. All-purpose flour (10 to 12 percent protein) produces a tighter, denser loaf but is perfectly edible and forgiving for beginners. Whole wheat, rye, and spelt each bring their own flavor and handling quirks, and most bakers blend them with bread flour rather than use them alone.

The protein percentage matters because sourdough ferments slowly — 12 to 48 hours depending on your kitchen temperature — and that long rise demands flour strong enough to hold its shape without collapsing. Weak flour (like cake flour at 8 percent protein) will spread into a pancake. The choice between bread and all-purpose usually comes down to what you have on hand and how much rise you want.

Key Takeaways

  • Bread flour (12 to 14 percent protein) produces the tallest loaf with the biggest holes because it develops gluten strength during the long fermentation.
  • All-purpose flour (10 to 12 percent protein) works fine and is more forgiving; your loaf will be denser but still good sourdough.
  • Whole wheat and rye add flavor and nutrition but absorb more water, so reduce your hydration by 5 to 10 percent if you use more than 20 percent of either.
  • Avoid cake flour and pastry flour — they lack the protein to support a sourdough's long rise and will spread flat.
  • Blending flours (70 percent bread flour plus 30 percent whole wheat, for example) gives you flavor without sacrificing structure.

Bread flour versus all-purpose: what the difference means in your loaf

Bread flour's extra protein (usually 2 to 4 percentage points higher than all-purpose) creates more gluten strands. During sourdough's slow fermentation, those strands stretch and hold the gas bubbles the starter produces. The result is a taller loaf with larger, more irregular holes — the open crumb that many bakers chase.

All-purpose flour has less protein, so it develops fewer gluten strands. Your dough will still rise, but more slowly and less dramatically. The crumb will be tighter and more uniform — smaller holes, denser texture. This is not a flaw. Many people prefer a tighter crumb for sandwiches, and the flavor is identical. All-purpose is also cheaper and sits in most home pantries already.

The practical difference: if you use all-purpose, expect your bulk fermentation to take 20 to 30 percent longer, and your final loaf to be 10 to 20 percent shorter. Your oven spring (the rise that happens in the first 10 minutes of baking) will be less dramatic. The bread will still taste like sourdough.

Whole wheat and rye: adding flavor at the cost of handling

Whole wheat flour contains the bran and germ, which absorb water like a sponge. If you replace 20 percent of your bread flour with whole wheat, your dough will feel drier and tighter than usual. The fix is straightforward: add 2 to 3 percent more water to your recipe. A 500-gram dough at 75 percent hydration becomes 500 grams at 78 percent hydration.

Rye behaves similarly but more dramatically. Rye bran is even more absorbent, and rye gluten is weaker — it stretches instead of holding firm. A dough that is 30 percent rye will feel slack and sticky compared to the same dough made with all bread flour. Reduce your hydration by 5 percent, handle it gently (overworking rye dough tears the gluten), and expect a denser, more flavorful loaf with a slightly sour tang.

Both whole wheat and rye add nutty, earthy flavor that pure white flour cannot match. Most bakers use them as a minority ingredient — 10 to 30 percent of the total flour — blended with bread flour to keep the structure intact while gaining flavor.

Spelt, einkorn, and heritage grains: flavor-forward but fragile

Spelt and einkorn are ancient wheat varieties with lower protein and weaker gluten than modern bread wheat. They ferment faster, meaning your bulk fermentation might finish in 4 to 6 hours instead of 12 to 18. They also oxidize quickly — the dough darkens and loses some flavor if you leave it too long. Handle them gently and watch your dough closely.

These grains taste distinctly different: spelt has a slightly sweet, nutty flavor; einkorn is earthier and more complex. If you want to use them, blend them at 20 to 30 percent with bread flour. A 100 percent spelt loaf is possible but demands experience — the dough is sticky, ferments unpredictably, and spreads easily.

Heritage grains are also more expensive and harder to find. Most home bakers encounter them at farmers markets or specialty shops rather than supermarkets. If you are curious, buy a small bag and experiment with a 25 percent blend before committing to a larger purchase.

Protein percentage: how to read the bag and predict your results

The nutrition label on flour bags lists protein as a percentage of total weight. Bread flour typically says 12 to 14 percent; all-purpose says 10 to 12 percent. This number predicts how much gluten your dough will develop and how tall your loaf will rise.

Different brands vary slightly. King Arthur Baking Company bread flour is 12.7 percent protein; Bob's Red Mill bread flour is 12 percent. Both work well for sourdough. All-purpose flours range from 10 to 12 percent depending on brand and region — Southern all-purpose is often lower (around 9 percent) because it was historically milled for soft cakes and biscuits.

If you cannot find the protein percentage on the label, check the brand's website or call the mill. It is worth knowing, especially if you are switching brands and your dough suddenly behaves differently. A shift from 12 percent to 10 percent protein means your fermentation will take longer and your oven spring will be less dramatic — not a disaster, just something to expect.

Common mistakes: what happens when you choose the wrong flour

Using cake flour or pastry flour (8 to 9 percent protein) is the most common mistake. These flours are designed for tender cakes and pie crusts, not bread. Your sourdough dough will spread during fermentation instead of rising up, and you will end up with a flat, dense pancake instead of a loaf. If you have cake flour on hand, blend it 50-50 with bread flour to salvage it.

Bleached versus unbleached flour matters less than protein percentage, but unbleached flour ferments slightly faster because the bleaching process slows yeast activity. If you switch from bleached to unbleached, reduce your fermentation time by 10 to 15 percent. The flavor difference is negligible.

Self-rising flour (which contains salt and leavening) will ruin your sourdough. The salt will kill your starter, and the baking powder will cause the dough to rise too fast and collapse. Avoid it entirely.

Building a sourdough flour strategy for your kitchen

If you bake sourdough regularly, keep bread flour as your base. It is the most forgiving choice and produces the most dramatic results. A 5 or 10-pound bag costs $3 to $6 and lasts most home bakers 4 to 8 weeks.

Keep a smaller bag of whole wheat or rye on hand if you like experimenting with flavor. A 2-pound bag is enough to make 4 to 6 loaves at 20 percent inclusion. Store both in airtight containers in a cool, dry place — flour absorbs moisture and goes rancid if exposed to heat or humidity.

If all-purpose is what you have, use it. Your sourdough will be good. You will learn the timing and handling of your particular dough, and you can always switch to bread flour later once you understand how your starter and kitchen behave.

Frequently Asked Questions

Can I use only whole wheat flour for sourdough?

Technically yes, but it is difficult. Whole wheat absorbs so much water that the dough becomes sticky and hard to handle. It also ferments faster and spreads more easily. Most bakers who want a whole wheat loaf use 30 to 50 percent whole wheat blended with bread flour, which gives them the flavor they want without the handling headaches.

What if I only have all-purpose flour at home?

Use it. Your sourdough will work fine — it will just take longer to ferment and rise less dramatically. Expect your bulk fermentation to take 18 to 24 hours instead of 12 to 18, and your loaf to be slightly denser. The flavor will be identical.

Does the brand of flour matter?

Brand matters less than protein percentage. King Arthur, Bob's Red Mill, and store brands all make good bread flour. What matters is that you pick one and stick with it long enough to learn how your dough behaves. Once you switch brands, the fermentation timing might shift by 10 to 20 percent because protein percentages vary slightly.

Should I use organic flour for sourdough?

Organic flour works fine if the protein percentage matches conventional flour. Organic bread flour at 12 percent protein will behave the same as conventional bread flour at 12 percent protein. The main difference is cost — organic flour is usually 20 to 40 percent more expensive. Flavor difference is subtle and matters less than fermentation time and technique.

What happens if I blend multiple flours together?

Blending is one of the best ways to experiment. A straightforward blend is 70 percent bread flour, 20 percent whole wheat, and 10 percent rye. Increase your hydration by 3 to 5 percent to account for the whole grains' water absorption, and watch your fermentation time — it may shorten slightly because rye ferments faster. Keep notes on what you blend and how it turns out so you can repeat what works.