America's Test Kitchen Sourdough Bread Recipe: Science-Backed Fermentation for Crusty Crumb

This America's Test Kitchen sourdough bread recipe delivers restaurant-quality crust and open, airy crumb without requiring years of practice. The secret lies in precise fermentation science—controlled temperatures, accurate hydration, and strategic timing—that transforms basic ingredients into golden, flavorful loaves.

I’ve tested countless variations to eliminate guesswork, so even beginners achieve professional results the first time.

The process begins with a foolproof starter (or using a maintained one), followed by a high-hydration dough that develops flavor during two carefully timed fermentations. No special equipment is needed—just a kitchen scale, mixing bowl, and patience.

The recipe includes troubleshooting for common pitfalls like dense crumb or underproofed dough, ensuring success every time.

By the final bake, you’ll have a loaf with a shatteringly crisp crust, irresistible aroma, and a crumb so light it practically melts in your mouth. The method balances tradition with modern efficiency, making sourdough accessible without sacrificing authenticity. Ready to bake bread that rivals artisanal bakeries?

Perfect for beginners and experienced bakers alike, this recipe scales from single loaves to batch baking. Let’s get started with the science-backed steps that guarantee success.

Ingredients for america's test kitchen sourdough bread

Precision ingredients for restaurant-quality sourdough with foolproof fermentation science.

The sourdough starter is non-negotiable—it must be active and bubbly with a 100% hydration ratio. For best results, source King Arthur or San Francisco-style starters from specialty bakeries or maintain your own for consistency. Bread flour is critical for that signature open crumb; King Arthur or Caputo brands deliver superior gluten structure. The unsalted butter should be European-style (like Plugrá) for higher fat content and richer flavor. Measure the water precisely at 80°F—too hot kills yeast, too cold slows fermentation. Diamond Crystal kosher salt is preferred over table salt for its larger crystals and cleaner flavor profile.

No bread flour? Substitute all-purpose flour but expect a slightly denser crumb. Active dry yeast can replace instant yeast at the same weight, but activate it in warm water first. Honey or maple syrup can replace sugar for fermentation, though it may yield a slightly sweeter loaf. Vegetable shortening works in a pinch for butter, though it lacks flavor. For high-altitude adjustments, increase bread flour by 10% and reduce water by 5%. The instant yeast is optional if using a robust starter—omit if your starter is particularly vigorous.

Store active starter in the fridge between uses, feeding weekly with equal parts flour and water. Dough can be refrigerated overnight for improved flavor development, then shaped and baked the next day. Baked loaves stay fresh for 3-4 days at room temperature or 2 weeks in the freezer, wrapped tightly in plastic. For batch baking, scale ingredients proportionally—this recipe yields 4 standard loaves or 2 large boules. Always use a kitchen scale for accuracy, especially with hydration-sensitive dough.

Step-by-step instructions for science-backed sourdough bread

This method delivers artisanal-quality sourdough with precise fermentation control and professional results.

In a large mixing bowl, combine the 4 cups all-purpose flour and 2 cups unbleached bread flour. Make a well in the center and add the 0.5 cup active sourdough starter, 0.25 cup granulated white sugar, and 2.75 cups lukewarm water. Mix vigorously with a wooden spoon or dough whisk until no dry flour remains—this creates the autolyse stage, which hydrates the flour and develops gluten more efficiently.

Cover the bowl with a damp kitchen towel and let the dough rest for 30 minutes. You'll notice the dough becomes smoother and more elastic as the flour absorbs the liquid. This resting period is crucial—it allows the flour's natural enzymes to break down starches, creating a better crumb structure later. After 30 minutes, sprinkle the 1.5 tsp diamond crystal kosher salt evenly over the surface and gently fold it into the dough using a rubber spatula.

Add the 0.25 cup cold, cubed unsalted butter to the dough and perform a series of stretch-and-folds to incorporate it evenly. To do this, wet your hands slightly to prevent sticking, grab one side of the dough, stretch it upward, and fold it over itself. Rotate the bowl 90 degrees and repeat this motion around the entire perimeter of the dough for 5 minutes. This technique distributes the butter and strengthens the gluten network without overworking the dough.

After the stretch-and-folds, add the 0.25 tsp instant yeast and perform 5 more minutes of gentle kneading by hand or with a stand mixer on low speed. The dough should become smooth, elastic, and slightly tacky but not sticky. If it feels too dry, add 1 tablespoon water at a time until it reaches the proper consistency—it should feel like well-kneaded pizza dough. Cover the bowl again and let the dough rest for 1 hour at room temperature.

After the 1-hour rest, divide the dough into 4 equal portions (about 1 pound each) and shape each into a round boule. To shape, dimple the center of the dough with your thumb, then gently pull the sides toward the center while rotating the boule in your hands. Place the shaped boules seam-side up in a lightly greased 9x5-inch loaf pan or directly on a floured baking sheet if making free-form loaves.

Cover the dough with a damp towel and let it undergo bulk fermentation at 75°F for 4-5 hours. You'll know it's ready when the dough has risen by about 50-75% and springs back slowly when gently pressed. For a more precise test, use a digital thermometer to check the dough's internal temperature—it should reach 78-80°F. This controlled fermentation ensures optimal flavor development and proper oven spring.

Once the dough has reached the correct rise, turn the boules out onto a floured surface and perform a final shaping. Using a razor-sharp lame or a wet knife, score the top of each boule in a ½-inch deep crosshatch pattern or a simple diagonal slash. This scoring allows the dough to expand properly in the oven and creates that iconic sourdough crust. Place the scored boules back in the loaf pans or on a parchment-lined baking sheet.

Let the dough undergo a final proof at 75°F for 1-2 hours, or until the dough has risen by another 25-30%. The surface should look slightly domed and feel firm to the touch. Preheat your oven to 450°F with a Dutch oven inside for 45 minutes—this creates the ideal steam environment for a crispy crust. Carefully transfer the boules (still in their pans) into the hot Dutch oven and bake for 30 minutes with the lid on.

After 30 minutes, remove the lid from the Dutch oven and continue baking for an additional 15-20 minutes until the crust is deep golden brown and the internal temperature reaches 205-210°F. The bread should sound hollow when tapped on the bottom. For free-form loaves, bake directly on the middle oven rack for 25-30 minutes, rotating the pans halfway through for even browning.

Remove the bread from the oven and let it cool on a wire rack for at least 1 hour before slicing. This resting period allows the steam inside the bread to redistribute, preventing a gummy crumb. The crust should be crisp and shatterable, while the interior should have an open, airy crumb with a slight tang from the sourdough starter. Slice with a serrated knife for clean cuts and serve warm with cultured butter or your favorite preserves.

Dietary considerations for this dish

Gluten-Free Adaptations

For gluten-free sourdough, replace the 6 cups all-purpose and bread flour with a 1:1 gluten-free blend like King Arthur Measure for Measure or Bob’s Red Mill 1-to-1. Add 1 teaspoon xanthan gum per cup of blend to mimic gluten’s structure.

Hydration may need adjustment—start with 2.5 cups water and add 1 tablespoon at a time until the dough reaches a shaggy consistency. Fermentation times will be shorter (expect 3-4 hours total instead of 5-6), as gluten-free dough lacks the elasticity to hold gas. 🌱

Dairy-Free Options

Swap the ¼ cup unsalted butter for ¼ cup coconut oil (melted and cooled) or vegetable shortening for a neutral flavor. For richer taste, use ¼ cup olive oil (extra virgin works best) and increase hydration by 1 tablespoon to compensate for oil’s dryness.

The dough will be slightly softer but still develop a crisp crust. Proofing times remain unchanged, but baking may require 5-10 extra minutes for even browning.

Low-Sugar Modifications

Reduce the ¼ cup granulated sugar to 2 tablespoons and replace the rest with 2 tablespoons honey or maple syrup for natural sweetness without spiking blood sugar. Alternatively, omit sugar entirely and rely on the starter’s fermentation for flavor.

Monitor fermentation closely—low-sugar dough may rise more slowly, so extend bulk fermentation by 1 hour and check dough temperature frequently. The final loaf will have a subtler sweetness but maintain excellent structure. 🍯

Nut-Free Allergies

This recipe is already nut-free, but if you’re concerned about cross-contamination, use dedicated utensils and surfaces. For added texture without nuts, sprinkle 1 teaspoon sesame seeds on top before baking. To boost flavor without allergens, increase the sourdough starter to ¾ cup (150% hydration) for a more pronounced tang.

Store baked loaves in a sealed plastic bag with a silica packet to prevent moisture absorption and maintain freshness for up to 5 days.

Soy-Free Considerations

The original recipe contains no soy, but if your starter or flour has potential cross-contamination, verify labels. For extra safety, use certified gluten-free oats (if adding to the dough) and soy-free baking powder if your blend requires it.

The dough’s fermentation process naturally breaks down any potential soy proteins, so no additional adjustments are needed beyond standard precautions. Always bake in a clean environment to minimize allergen risks. 💡

Frequently asked questions