What Is Sourdough and How Does the Baking Process Work?

Updated

Sourdough is bread leavened by a living culture of wild yeast and bacteria—called a starter—rather than by commercial yeast. You can bake it at home with just flour, water, salt, and time, but it demands patience: the starter must be active, and the dough needs long fermentation and proofing periods. If you want predictable, same-day bread, commercial yeast is simpler; if you want deeper flavor, a chewier texture, and a process you can learn and adjust, sourdough is worth the effort.

What makes sourdough different

A sourdough starter is a flour-and-water mixture that captures wild yeast and lactic acid bacteria from the environment and from the flour itself. Regular feeding keeps that culture alive and builds its rising power.

Factor Sourdough Commercial yeast bread
Leavening Wild yeast in a maintained starter Packaged yeast
Time Hours to days (starter + bulk + proof) Often same day
Flavor Tangy, complex, varies by starter and schedule Cleaner, more neutral
Texture Open crumb, chewy crust Softer, more uniform
Skill focus Reading dough and timing Measuring and following a schedule

The tang comes from acids produced by bacteria during fermentation. How sour the loaf tastes depends on your starter, hydration, temperature, and how long you ferment.

The starter: your leavening engine

The starter is the part beginners most often get wrong. It needs regular feeding—typically discarding some of the old mixture and adding fresh flour and water—so the yeast and bacteria have food and the culture stays balanced.

A starter is ready to bake with when it rises predictably after feeding, looks bubbly and domed, and smells pleasantly yeasty or tangy rather than sharply acetone-like. If it isn't rising, the usual causes are infrequent feeding, cold conditions, or a young culture that hasn't matured yet. The Fresh Loaf community has extensive troubleshooting threads on exactly this problem.

The core process, step by step

  1. Build or refresh the starter. Feed it and wait until it's active and expanded. This is your input; the expected result is a bubbly, risen culture.
  2. Mix the dough. Combine starter, flour, water, and salt. Rest to let the flour hydrate.
  3. Bulk ferment. Let the dough rise as a mass, folding it periodically to build strength. You're looking for visible expansion, a domed top, and a dough that feels airy.
  4. Shape. Divide and form the dough into loaves, creating surface tension.
  5. Proof. Let the shaped loaves rest until slightly puffy and ready—this is the stage where underproofing most often happens.
  6. Bake. Score the top and bake with steam for the first part, then dry heat for crust color. The loaf should sound hollow and have a browned crust.

Each step changes the dough, so the useful skill is observing rather than only watching the clock.

Common beginner pitfalls

  • Weak starter: dough won't rise no matter how long you wait. Fix the starter first.
  • Underproofing: dense, gummy crumb and poor oven spring. Give the shaped loaf more time.
  • Overproofing: collapsed, flat, or overly sour loaf. Shorten the proof or cool the dough.
  • Inconsistency: results change with room temperature, flour, and starter strength. Keep notes so you can repeat what worked.

Where to go for recipes and help

The Fresh Loaf (thefreshloaf.com) is a community site for artisan and amateur bakers, with recipes, news, and discussion threads. It's a practical place to compare methods, ask about a starter that won't rise, or troubleshoot a loaf that came out dense. Start with one reliable recipe, keep your starter on a consistent feeding schedule, and adjust one variable at a time.