Wild Sourdough Starter — Building and Maintaining

A sourdough starter is a living culture of wild yeasts and lactic acid bacteria (LAB) maintained in a flour-and-water medium, capable of leavening bread and imparting complex flavour through organic acid production and protease activity. Building a wild starter from scratch harnesses the microbial ecology of flour, water, and the baker's environment — different locations, flour mills, and water chemistry produce genuinely distinct starter profiles. The establishment process typically takes 7–14 days. Initially, diverse microorganisms colonise the fresh flour-water mixture, producing erratic and often foul-smelling fermentation as heterogeneous bacteria compete. As the baker begins regular feeding — discarding a portion and adding fresh flour and water — conditions are shaped toward a stable pH (approximately 3.5–4.0 after peak activity) that selects strongly for acid-tolerant wild yeasts (primarily Kazachstania humilis, formerly Candida humilis) and heterofermentative LAB (Lactobacillus sanfranciscensis being the most studied). This succession — from chaotic to stable — takes 7–10 days of regular feeding. Hydration ratio (the ratio of water to flour by weight) determines starter consistency and flavour character. 100% hydration (equal weight flour and water) produces a pourable, active starter with moderate acidity. Lower hydration (60–70%) creates a stiff starter with higher acidity and different yeast-LAB ratios. Many bakers maintain a liquid 100% hydration starter for everyday use and a separate stiff 65% levain for specific bread applications. Once established, a starter requires regular feeding to remain active. At room temperature (22–24°C), a 1:1:1 ratio (starter:flour:water by weight) fed once or twice daily maintains peak activity. Refrigeration slows metabolism, allowing weekly feeding. Before use in a recipe, the starter must be fed and allowed to peak — typically doubling to tripling in volume — at which point yeast activity and LAB acid production are at their highest.

Serves1 active starter

Total5–7 days (plus ongoing maintenance)

Sourced1of 2 in BC

Cook

The Market List

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100 g

whole rye flour (or unbleached bread flour)

Origin · GermanyLekker · Vancouver →

100 ml

filtered or dechlorinated water (room temperature)

Not yet stocked in British Columbia

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The Method

Combine 100 g rye flour and 100 ml water in a clean glass jar; stir until homogeneous and leave uncovered at room temperature (68–72 °F / 20–22 °C).

Observe for 24–48 hours; wild yeast and Lactobacillus will colonize the mixture, producing bubbles and a slightly sour aroma.

Discard half the starter (50 g) and feed with 50 g flour and 50 ml water; stir, cover loosely, and rest 24 hours.

Repeat step 3 daily for 5–7 days until the starter doubles predictably within 4–8 hours of feeding and shows a pleasant, tangy smell with a stable ratio of rising/falling cycles.

Once mature and doubling reliably, refrigerate between feedings; feed once weekly or before use (remove from cold storage 12 hours ahead, feed, allow to peak at room temperature, then refrigerate).

For baking, use starter at its peak (fully risen, visibly bubbly, doubled in volume from feed); discard half, feed with flour and water equal to the remaining mass, and let rise 4–6 hours before incorporating into dough.

Sensory Tests

◇Sight. Look for a spoonful to float on water and smell clean, yeasty bread rather than acetone or rotting fruit — this signals the wild yeast population has dominated.

◇Where it lives or dies. Feed at consistent ratios every 24 hours for 7–14 days; skip even one cycle and acidity crashes below the threshold where yeast can work.