Surdej

Surdej, or sourdough starter, is a living culture of wild yeasts and lactic acid bacteria used to leaven bread. It is created by mixing flour and water and allowing natural microorganisms present in flour and the surrounding environment to proliferate. The resulting culture contains a balance of yeasts that produce carbon dioxide and bacteria that generate lactic and acetic acids, giving both leavening and flavor.

Maintenance and feeding: A starter is kept by regularly feeding it with fresh flour and water. Common practice is to weigh equal parts starter, flour, and water (100% hydration) or to vary hydration depending on tradition. After each feeding, the mixture becomes bubbly and rises; this activity indicates readiness for bake. If not baked daily, it can be refrigerated and fed weekly to slow fermentation. When revived, the starter should double in size within several hours at room temperature.

Microbiology: The precise species vary, but Lactobacillus bacteria pair with wild yeasts; Lactobacillus sanfranciscensis is a well-known example in sourdough. The acid production creates the characteristic tang and improves dough handling and shelf life.

Baking use and flavor: Surdej replaces commercial yeast in many breads, especially rustic loaves and rye breads. It contributes complex flavor, a tender crumb, and a crisper crust. Fermentation temperature and duration influence aroma, crumb structure, and acidity.

Variations and storage: Starters can be stiff or liquid, affecting fermentation rate and flavor. They can be developed with different flours such as wheat, rye, or spelt. For long-term storage, refrigerate or freeze; discard part of the starter during feeds to manage acidity and volume.