Food

Sourdough

Also known as: Sourdough bread, Naturally-leavened bread

Bread leavened by a wild-fermented starter culture — a stable symbiosis of wild yeasts (primarily Saccharomyces and related species) and lactic acid bacteria (Lactobacillus, Pediococcus) — rather than commercial baker's yeast. The original form of leavened bread; the dominant bread tradition for ~6,000 years until commercial yeast arrived in the late 19th century. Sourdough's slower fermentation produces more digestible bread (lower phytic acid, lower gluten, lower glycemic index), more flavor complexity, and bread that keeps longer. A starter, properly maintained, can persist for generations — household starters of 100+ years are documented.

What sourdough is

A [[sourdough-starter|sourdough starter]] is a stable mixed culture of:

Wild yeasts — primarily Saccharomyces and related species, plus various Candida, Kazachstania, etc., depending on flour and environment. The yeasts ferment sugars, producing CO₂ (which leavens the bread) and ethanol.
[[lactic-acid|Lactic acid]] bacteria (LAB) — primarily Lactobacillus sanfranciscensis and related species. The LAB ferment maltose and other sugars, producing lactic and acetic acids (which give sourdough its characteristic tang).

The yeast and bacteria coexist stably because they consume different sugars and the acidic environment the LAB produce favors the yeasts that thrive in it.

Why it works differently than commercial-yeast bread

Slower — sourdough fermentation typically takes 8–24+ hours. Commercial yeast does the same job in 1–2 hours.
More digestible — the long slow fermentation predigests starches, breaks down phytic acid (a mineral-binding antinutrient in grains), and partially breaks down gluten (still not safe for celiac diagnoses, but tolerable for many gluten-sensitive eaters)
Lower glycemic index — fermented starches release sugar more slowly than fresh-yeast-only bread
Flavor — hundreds of fermentation byproducts produce flavor complexity that fast-fermented bread cannot
Keeps longer — the acid environment and the lower water activity inhibit mold and staling

Practice

Maintaining a starter:

Mix flour and water (typically equal weights)
Wait 5–7 days at room temperature, feeding daily, until the culture is active and consistent
Continue feeding at intervals matched to use frequency (daily for active baking; weekly with refrigeration for occasional baking)

Baking with sourdough requires more time and observation than commercial yeast — the timing depends on the starter’s vigor, temperature, and flour. Once a baker develops the rhythm, the practice becomes deeply intuitive.

Tradition

Sourdough is the original leavened bread. The Egyptian, Roman, and medieval European bread traditions; the rye breads of Northern Europe; the injera of Ethiopia; the dosa and idli of South India; the baguette of pre-industrial France — all are sourdough traditions in their respective forms.

The Boudin Bakery in [[mission-district-sf|San Francisco]] has maintained the same starter since 1849 — among the oldest continuously-cultivated cultures documented. Many sourdough bakers maintain household starters of multiple decades; some pass them down generationally.

Sources

Tartine Bread, Chad Robertson (Chronicle, 2010)
Flour Water Salt Yeast, Ken Forkish (Ten Speed, 2012)
[[the-art-of-fermentation|The Art of Fermentation]], [[sandor-katz|Sandor Ellix Katz]]

Rooted in life.

What links here, and how

Inbound connections from across the wiki, grouped by lens and by relationship. These appear automatically — every entity page declares what it links to, and that data populates here on the targets.

Scientific

substrate of

Lacto-fermentation sourdough's signature tang and digestibility come from lacto-fermentation alongside wild-yeast leavening

Practical

contains

Preservation toolkit ferment / wild-yeast bread

2 inbound links · 3 outbound