Learn How to Make Sourdough Bread From Starter

Understanding Sourdough Starter: What It Is and How It Works

A sourdough starter is a living culture of wild yeast and beneficial bacteria that ferments flour and water. Unlike commercial yeast packets, which contain a single strain of yeast, a sourdough starter contains multiple microorganisms that work together to leaven bread. The primary microorganism responsible for rising is Saccharomyces cerevisiae, a wild yeast that naturally exists on grain and in the environment. The bacteria, primarily Lactobacillus, produces lactic acid, which gives sourdough its characteristic tangy flavor and improves digestibility.

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Creating a starter takes about five to seven days. You begin by mixing flour and water in a jar, then feed it daily by discarding half the mixture and adding fresh flour and water. During this period, you'll notice bubbles forming, which indicates fermentation is occurring. The smell may progress from unpleasant to pleasant as beneficial bacteria colonize the mixture and less desirable microorganisms die off. This natural selection process means your starter develops based on the flour you use, your local environment, and your water quality. Two starters maintained in different locations will have slightly different bacterial populations and may produce bread with subtle flavor variations.

The maturity of your starter affects bread quality significantly. A young starter (one to two weeks old) may produce bread with less rise and milder flavor. A mature starter (four weeks or older) typically has more developed flavor and better leavening power. Temperature also influences starter activity. A starter at 75°F to 80°F ferments faster than one at 65°F to 70°F. Understanding these variables helps you predict how your starter will behave and adjust your baking timeline accordingly.

Practical takeaway: Begin your starter at least one week before you plan to bake. Store it in a container that holds at least four times the volume of your starter mixture to accommodate expansion during fermentation. A clear glass jar allows you to observe activity and judge when feeding is necessary.

Building and Maintaining Your Starter for Consistent Results

Maintenance is straightforward once your starter is established. Most bakers feed their starter once daily at room temperature or once weekly if refrigerated. A basic maintenance schedule involves removing half the starter (called the discard) and adding equal weights of flour and water. For example, if your starter weighs 100 grams, you remove 50 grams and add 50 grams of flour and 50 grams of water. This creates a ratio of 1:1:1 (starter to flour to water), which is called a "feed ratio" or "maintenance ratio."

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The type of flour you use matters. Whole wheat and rye flours contain more nutrients and ferment slightly faster than all-purpose flour, though they may produce a starter with stronger sourness. All-purpose flour creates a milder starter and is the most commonly used option. Bread flour, with its higher protein content, supports strong gluten development in the final dough. Many bakers maintain their starter with all-purpose flour and then use bread flour for baking. Water quality also plays a role—chlorinated tap water may slow fermentation, so filtered or dechlorinated water is preferable, though tap water often works adequately.

Storing your starter extends the time between feedings and reduces flour waste. Refrigeration slows fermentation dramatically. A starter stored at 40°F may require feeding only once weekly or even less frequently. Before baking, remove the refrigerated starter and feed it at room temperature one to two times over several hours until it shows vigorous activity (doubling in size within four to eight hours after feeding). This is called "activating" the starter, though it's technically just warming it to its optimal fermentation temperature and ensuring sufficient food is available.

Practical takeaway: Weigh your starter and feed water using a kitchen scale rather than measuring by volume. This precision reduces variation and helps you understand fermentation rates. If you travel or bake infrequently, refrigerate your starter. Feed it before refrigerating and then restore room-temperature maintenance when you plan to bake again.

Preparing Your Dough: Mixing and Initial Fermentation

A basic sourdough dough contains only four ingredients: flour, water, salt, and starter. A typical recipe uses 500 grams of flour, 350 grams of water (70% hydration), 100 grams of active starter, and 10 grams of salt. The ratio of flour to water, called hydration percentage, affects dough texture and crust characteristics. Lower hydration (60% to 65%) produces denser crumb and thicker crust. Higher hydration (75% to 80%) creates more open crumb structure and crispier crust but requires more experience to handle. Most beginning bakers start at 70% hydration.

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Mix the flour and water first, combining them until no dry flour remains. Let this mixture rest for 30 minutes to one hour—a process called "autolyse." This rest period allows flour to fully absorb water and begins gluten development naturally without mixing. After autolyse, add the starter and salt, mixing until fully incorporated. Mix either by hand, squeezing the dough repeatedly in the bowl, or with a stand mixer on low speed for five to ten minutes.

After mixing, the dough enters bulk fermentation, typically lasting four to six hours at room temperature. During this phase, yeast produces gas that creates bubbles throughout the dough, while bacteria develop flavor through fermentation. Rather than a single long rise, most bakers perform "stretch and folds" every 30 minutes during the first two hours. This involves grabbing one side of the dough, stretching it upward, and folding it over the center, rotating the bowl and repeating from four directions. These folds strengthen the dough structure without additional mixing and help distribute nutrients evenly. After two hours of stretching and folding, leave the dough undisturbed until bulk fermentation is complete. The dough should increase in volume by 50% to 100% and show visible bubbles under the surface.

Practical takeaway: Use a clear container for bulk fermentation so you can observe dough progress without disturbing it. Mark the starting level with tape or a marker to judge volume increase accurately. If your kitchen is cold (below 70°F), increase fermentation time; if warm (above 75°F), reduce it slightly.

Shaping and Cold Fermentation: Developing Flavor and Structure

After bulk fermentation, the dough is ready for shaping. Turn it onto a lightly floured surface and gently shape it into a round ball (boule) or oval loaf (batard). When shaping, you're creating surface tension that helps the dough rise upward in the oven rather than spreading outward. For a boule, fold the dough over itself from all sides, working in a circular pattern, then flip it seam-side down. For a batard, fold it in thirds lengthwise and then roll it tightly toward you. Avoid degassing the dough completely—gentle handling preserves the bubbles created during bulk fermentation.

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The shaped dough goes into a banneton (a cloth proofing basket) seam-side up, or you can use a bowl lined with a floured kitchen towel. This is where cold fermentation occurs. Rather than proofing at room temperature for one to two hours, many bakers refrigerate the shaped dough overnight (8 to 16 hours) at 38°F to 40°F. Cold fermentation has several advantages: it develops complex flavors because fermentation continues slowly in the cold, making the dough more sour and nuanced; it makes scoring easier because cold dough is stiff; and it fits naturally into many daily schedules—you can shape dough in the evening and bake it the next morning.

If you prefer room-temperature proofing, the dough typically needs two to four hours before it's ready to bake. It should pass the "poke test"—gently press a floured finger into the dough surface about half an inch deep. If the dent slowly springs back halfway, the dough is ready. If it springs back completely, fermentation isn't complete. If it doesn't spring back at all, the dough is overproofed. Overproofed dough spreads instead of rising and produces a denser crumb. Finding the right proofing time depends on room temperature, starter strength, and hydration—keeping notes from your bakes helps you dial in