Food & Cooking
Sourdough Starter
A live culture of wild yeast and lactic-acid bacteria kept alive by regular flour + water feedings. The leavening engine for sourdough bread.
View on brothh.comWhat it means
A sourdough starter is a self-sustaining colony of wild yeast (primarily Saccharomyces species) and lactic-acid bacteria (Lactobacillus) living in a flour-and-water paste. The yeast leavens the bread; the bacteria produce the acid that gives sourdough its tang and extends shelf life.
A healthy starter doubles within 4-8 hours of feeding at 70-75°F. Feeding ratios (starter : flour : water) control the rate: 1:1:1 peaks in ~4 hr, 1:5:5 in ~10 hr. Most bakers keep a 100% hydration starter (equal parts flour and water by weight).
Examples
Daily feed (on counter)
Discard all but 50g, feed 50g flour + 50g water (1:1:1)
Fridge hold (1x weekly)
Feed before refrigerating; warm + 2 feeds before baking
Do
- Use unchlorinated water — chlorine kills the culture.
- Use whole grain or a rye/whole-wheat mix to boost activity.
Don't
- Feed with cold flour from the fridge — it slows fermentation.
- Expect peak activity on a starter under 2 weeks old.
Related terms
Calculators that use this
Sourdough Starter Feeding
Compute flour, water, and ripe time for any starter feed ratio and target hydration.
Dough Hydration
Baker percentage math for flour, water, salt, and levain — get the ratios right every bake.
Yeast Converter
Convert between active dry, instant, and fresh yeast — with baker’s percentage when you give flour weight.