Sourdough starter

A live culture of flour and water that holds wild yeasts and lactic acid bacteria, kept active with regular feedings and used to raise bread and other doughs.

Sourdough starter: A glass jar of bubbly, risen sourdough starter with a spoon resting beside it, bubbles visible through the glass
  • Baking ingredients and additives

Also called: levain, natural leaven

A starter begins as a simple paste of flour and water left at room temperature. Over several days, yeasts and bacteria from the flour and the air settle in and multiply. Each feeding means discarding part of the starter and adding fresh flour and water, which keeps the culture lively and its sourness in balance.

A healthy starter smells pleasantly tangy, looks bubbly and rises noticeably within several hours of a feeding. Bakers use it at or near its peak, when it is most active. Kept in the refrigerator between bakes, a starter slows down and needs only an occasional feeding.

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Sources

Written by VanillaGoods in our own words from these sources. Last reviewed October 15, 2026.

  1. Sourdough Starter Best Practices, Colorado State University Extension