Doughs & batters
sourdough starter
levain · A fermented culture of wild yeasts (predominantly Saccharomyces exiguus, Candida milleri) and lactic acid bacteria (Lactobacillus species) maintained in a flour-water medium. The symbiotic culture metabolizes starches and simple sugars, producing carbon dioxide for leavening and a balanced blend of organic acids (primarily lactic and acetic) that provide the characteristic tang, shelf life, and biological preservation. The starter is the living, self-propagating foundation of all traditional sourdough baking and cannot be replaced by commercial yeast alone.
The formula
1:1:1 by weight starter : flour : water
Mature maintenance: 50g starter + 50g flour + 50g water = 150g total; discard to 25–50g before each feeding. For peak activity, expect doubling in 4–8 h at 24°C (75°F). Initial culture: 100g whole grain flour + 100g water. Build for bread: 20–40% of flour weight as active starter.
Identity
- Wild yeast-dominant fermentation producing reliable leavening power
- Lactic and acetic acid blend creating balanced sourness (pH 3.5–4.5)
- Consistent doubling and peak rise within 4–8 hours when mature
- Complex, floral-to-tangy aroma with no ammonia, rot, or rank putridity
- Float test: 1 tsp mature starter floats in water
- Self-propagating culture maintained indefinitely through regular feeding
Ingredients
| Base | Whole grain flour (whole wheat, rye, or spelt) | Initial culture requires nutrient-rich germ and bran. For maintenance, unbleached all-purpose works; whole grain builds activity faster. |
| Liquid | Chlorine-free water | Chlorine and chloramine inhibit bacteria. Use filtered water or let tap water stand uncovered 24 hours to dissipate chlorine. |
Method
- 1Day 1: Combine 100g whole grain flour with 100g room-temperature water (21–24°C / 70–75°F). Mix thoroughly in a non-reactive glass or ceramic container.Creates an anaerobic fermentation medium. Wild yeasts and bacteria from the flour surface and environment inoculate the culture.
- 2Cover loosely (loose lid, cloth, or plastic wrap with a few holes). Rest at room temperature 24 hours.Allows natural fermentation to initiate. The flour's native microbes begin colonization while undesirable organisms are outcompeted by the fermentation environment.
- 3Day 2: Discard all but 25–50g of the mixture. Add 50g flour and 50g water. Stir vigorously, cover, rest 24 hours.Back-slopping—retaining a portion of the previous fermentation—ensures the desired microbial community dominates. Discarding controls population size and prevents over-acidification.
- 4Days 3–7: Feed every 12–24 hours using the 1:1:1 ratio. Maintain at 20–24°C (68–75°F).Consistent feeding builds and maintains a robust, predictable population of yeasts and bacteria. The culture is mature when it reliably doubles in 4–8 hours and smells pleasantly tangy-sweet.
- 5Once established (5–14 days), transition to refrigerator storage: feed once, let peak at room temperature, then seal and refrigerate.Cold (4–5°C / 39–41°F) dramatically slows metabolism, allowing weekly maintenance instead of daily feeding. The sealed container prevents drying and contamination.
Techniques that matter
Back-slopping (inoculation)
Intentionally retaining a portion of a previous fermentation to propagate and stabilize the desired microbial community; the foundation of all cultured starters.
Wild yeast cultivation
Capturing and domesticating ambient yeasts from flour, air, and environment rather than using isolated commercial strains; produces more complex fermentation flavors.
Temperature-controlled fermentation
Warm temperatures (24–27°C) accelerate fermentation and favor lactic acid production; cooler temperatures (18–21°C) slow activity and favor acetic acid, intensifying sharpness.
Peak fermentation timing
Using the starter at its maximum rise (doubled volume, domed top, beginning to fall) ensures maximum leavening power and optimal flavor contribution.
Variations & derivatives
Rye sourdough starterCentral and Eastern Europe
Rye flour's arabinoxylan structure and higher sugar content produce faster, more aggressive fermentation. Rye starters are typically kept at higher hydration (100–125% water) and develop intense, distinct tang.
Liquid levain (levain liquide)France
Higher hydration (125–150% water to flour) produces milder acidity, better distribution in batter-based recipes, and lighter crumb contribution. Preferred for pain de campagne and baguettes.
Stiff levain (levain dur)France
Lower hydration (50–60% water to flour) creates concentrated, intensely acidic culture with better shelf stability. Ideal for enriched doughs where the starter must not add excessive moisture.
Pizza dough starter (biga americana)United States, Italy
A relatively firm, aged biga used specifically for pizza; typically maintained at lower hydration (55–60%) and shorter fermentation for chewy, blistered crusts.
Used in these dishes
Substitutions
- Sourdough starter → Commercial active dry yeast — Can leaven bread but produces none of the characteristic sour flavor, complex aromatic compounds, or natural preservation. Use 7g dry yeast per 500g flour as rough substitution for 100g active starter.changes result
- Sourdough starter → Poolish (flour-water culture) — A thin, 100% hydration preferment using commercial yeast; similar crumb texture but lacks sourness. 1:1 substitution by weight possible for non-sourdough breads.
- Sourdough starter → Pâte fermentée (old dough) — A piece of previous bread dough saved and refrigerated; contains some wild yeast activity and acid development. Use 20% of total flour weight as you would a stiff starter.
Troubleshooting
Mold on surface (pink, orange, green, or black fuzz)
Neglect beyond 2–3 weeks or contamination from unsanitary vessel. The acidic environment normally suppresses this, but extended dormancy allows mold to colonize. → Discard the entire culture immediately. Start a fresh culture from 100g whole grain flour and 100g water. Do not attempt rescue with surface-scrubbing.
Sluggish fermentation: no rise after 12–16 hours
Weak or dormant culture, refrigerator-cold temperature, depleted nutrients, or too-small inoculation ratio. → Bring to room temperature; feed with whole grain flour (more nutrients); increase feeding ratio to 1:2:2; repeat twice daily for 2–3 days until vigorous.
Hooch (thin, gray-to-dark liquid pooling on surface)
Neglected starter; the culture has exhausted its food supply and begun metabolizing secondary compounds. The hooch is primarily ethanol and acetic acid. → Pour off hooch and feed immediately. The starter is still viable—this is normal aging, not spoilage. If the smell is foul (butyric or putrid), the culture may be dying; rescue with fresh flour and warm water.
Ammonia or fingernail-polish odor
Too much readily available nitrogen from refined white flour without balance; bacterial proteolysis producing ammonia compounds. → Switch to whole grain flour for 2–3 feedings; ensure feeding ratio is 1:1:1 and consistent; reduce room temperature slightly to slow activity.