Sourdough
Part of Fermentation and Brewing
Sourdough is one of the most important fermentation technologies for civilization rebuilding. It replaces commercial yeast entirely, using wild yeast and bacteria captured from flour and the environment to leaven bread. A healthy sourdough starter is self-perpetuating, free of cost, and improves with age. Every community capable of growing or storing grain can produce sourdough bread without external inputs.
What Is a Sourdough Starter
A sourdough starter is a flour-water mixture colonized by wild yeast (primarily Saccharomyces cerevisiae and Kazachstania humilis, also known as Candida humilis) and lactic acid bacteria (primarily Lactobacillus sanfranciscensis and related species). The wild yeast provides leavening power (CO2 gas); the bacteria produce lactic and acetic acids that give sourdough its characteristic flavor and improve its shelf life.
This community of organisms, once established, is maintained indefinitely through regular feeding — adding fresh flour and water. A well-maintained starter is essentially immortal: some bakeries maintain starters over 100 years old.
Capturing Wild Yeast: Starting a Starter
Starting a starter from scratch requires only flour, water, and time. The organisms colonize naturally from the flour itself and from the air.
Equipment
- A clean glass jar or ceramic crock (500 ml capacity or larger)
- Kitchen scale (strongly recommended) or consistent measuring containers
- Cloth or loose lid for covering
Day-by-Day Starter Development
Starting ratio: Mix by weight. Using equal weights of flour and water is the easiest to remember and calculate.
Day 1:
- Combine 50 g whole-grain flour (rye or whole wheat works fastest — they carry more wild yeast than white flour) + 50 g unchlorinated water
- Stir thoroughly; no dry lumps
- Cover loosely; leave at room temperature (20–24°C)
Day 2:
- Observe: possibly no activity yet; possibly a few bubbles
- Discard all but 50 g of the mixture
- Feed: add 50 g flour + 50 g water; stir well
Day 3:
- Activity should be visible: bubbles, slight dome forming, possible sour smell
- Discard all but 50 g; feed with 50 g flour + 50 g water
Day 4–5:
- More active: clear rising and falling pattern
- Discard and feed on the same schedule
Day 6–7:
- Fully active starter: doubles in size within 4–8 hours of feeding, develops a domed peak, then begins falling. Strong sour smell.
- Ready to bake with
The discard step is essential. If you do not discard before feeding, the starter grows exponentially, demanding ever-larger quantities of flour, and the bacterial population acidifies so rapidly that it inhibits the yeast. The small maintained volume — "seed culture" — keeps the population balanced and the flour consumption manageable. Use discarded starter in pancakes, flatbreads, or thin crackers rather than wasting it.
Troubleshooting Slow Starters
| Problem | Cause | Solution |
|---|---|---|
| No activity after 5 days | Chlorinated water; cold temperature; white flour only | Switch to spring water; warm to 25°C; add some rye flour |
| Hooch (gray liquid on top) | Starter hungry; fed too infrequently | Pour off hooch; discard more aggressively; feed twice daily |
| Pink or orange streaks | Contamination by non-desirable bacteria | Discard entire batch; start fresh with cleaner equipment |
| Very sour but not rising | Bacteria dominant over yeast | Feed with white flour (less acidic spike); reduce feeding frequency slightly |
| Rises but falls very quickly | Healthy but hungry; needs more flour per feeding | Increase flour-to-starter ratio: 1:2:2 (starter:flour:water) |
Flour Types and Their Effects
| Flour Type | Starter Behavior | Bread Character |
|---|---|---|
| Whole rye | Fastest, most active; highest wild yeast and enzyme content | Dense, strong sour flavor, dark |
| Whole wheat | Active; slightly slower than rye | Nutty, robust flavor, good rise |
| White wheat | Slower; lower wild yeast; cleaner flavor development | Mild tang, light crumb, longer shelf life |
| Spelt | Similar to wheat; slightly sweeter | Sweet-nutty, heritage grain flavor |
| Oat (oat flour) | Weak; cannot sustain a starter alone | Use as adjunct only (max 20%) |
A blended starter — 80% white wheat, 20% rye — provides reliable activity with mild flavor. A pure rye starter is the most vigorous option in cold conditions.
Feeding and Maintenance
Standard Feeding Ratio (1:1:1)
Discard all but 50 g of starter. Add 50 g flour and 50 g water. Stir. Cover loosely. Feed every 12–24 hours at room temperature.
Higher-Ratio Feeding (1:2:2 or 1:5:5)
For a milder, less acidic starter and a longer window between feedings:
- Keep 20 g starter; add 40 g flour + 40 g water (1:2:2)
- Keep 10 g starter; add 50 g flour + 50 g water (1:5:5)
Higher ratios dilute the acid more, slow the acidification rate, and extend peak activity. Use this when you need to bake less frequently.
Cold Storage
A starter stored in the refrigerator enters a dormant state and requires feeding only once per week:
- Feed at normal ratio.
- Allow to rest at room temperature for 1–2 hours (to begin activity).
- Seal jar and place in refrigerator.
- One week later: remove, let warm 1–2 hours, discard and feed as normal.
- If planning to bake: bring starter out 24 hours before needed; feed once at room temperature; it should be at peak within 4–8 hours.
A starter stored for several weeks without feeding becomes very acidic and may smell of alcohol and strong vinegar. It is not dead — it is dormant and acid-stressed. Revive it: discard all but 10 g, feed generously (10 g starter + 50 g flour + 50 g water), and repeat once daily for 3 days. A genuinely healthy starter almost always recovers.
Making Sourdough Bread
Recipe: Simple Country Sourdough (One Loaf, approximately 900 g)
Ingredients:
- 400 g white bread flour (or 360 g white + 40 g whole wheat)
- 290 ml water
- 80 g active starter (fed 4–8 hours prior; at its peak — domed, bubbly)
- 9 g non-iodized salt
Method:
1. Autolyse (30–60 minutes): Mix flour and water. No starter, no salt. Cover; rest 30–60 minutes. Gluten begins developing without kneading.
2. Add starter and salt: Add starter to the flour mixture; mix by folding and squeezing until fully incorporated. Add salt; mix again.
3. Bulk fermentation (4–12 hours depending on temperature): Leave the dough in a covered bowl at room temperature. Perform 4 sets of “stretch and fold” in the first 2 hours (every 30 minutes): wet your hands, grab one side of the dough, stretch it up, fold over the top. Rotate bowl 90°, repeat 4 times per set.
| Temperature | Expected Bulk Time |
|---|---|
| 18°C | 10–14 hours |
| 22°C | 6–10 hours |
| 25°C | 4–6 hours |
| 28°C | 3–4 hours (watch carefully) |
Bulk fermentation is complete when dough has grown 50–75%, feels lighter and gassy, and the surface shows bubbles. The underside (visible through a clear bowl) shows a network of large bubbles.
4. Pre-shape and bench rest (20–30 minutes): Turn dough onto an unfloured surface. Shape into a rough round by tucking edges under. Rest uncovered 20–30 minutes.
5. Final shape: Gently stretch the dough into a rectangle. Fold the top third down, the bottom third up (like a letter). Fold left side over right. Roll toward you into a tight cylinder or round. Place seam-side up in a floured proofing basket (banneton) or a cloth-lined bowl.
6. Cold proof (8–14 hours in refrigerator): Cover the basket tightly. Refrigerate overnight. The cold proof slows fermentation, improves flavor complexity, and makes scoring easier.
7. Bake: Preheat a Dutch oven (cast iron pot with lid) at maximum temperature for 45–60 minutes — if baking in a clay oven or hearth, ensure it is fully heated.
Turn the cold loaf directly from the basket onto a floured surface. Score the top with a sharp blade at 45° angle — at least one cut 5–8 cm long.
With Dutch oven: Place scored loaf in hot pot. Bake covered at maximum heat for 20 minutes (steam phase). Remove lid; bake 20–25 more minutes until deep brown.
Without Dutch oven: Bake on a stone or heavy pan. Place a pan of water in the oven for the first 15 minutes for steam. Remove water pan; continue baking 25–30 minutes.
8. Cool completely: The internal crumb continues cooking as it cools. Do not cut for at least 1 hour. Best flavor at 2 hours post-bake.
Expected Outcomes
| Factor | Indicator of Success |
|---|---|
| Oven spring | Loaf rises noticeably in first 10–15 minutes of baking |
| Crust | Thick, shattering crust; deep brown color |
| Crumb | Open, irregular holes; slightly moist; not gummy |
| Flavor | Mild to pronounced sour tang; complex, wheaty |
| Shelf life | Keeps 4–6 days at room temperature; does not mold quickly |
Maintaining a Starter Through Shortage
When flour is scarce, a starter can be maintained on minimal inputs:
- Minimum viable feeding: 10 g starter + 10 g flour + 10 g water (10 g total maintained culture)
- Drying for long-term storage: Spread a thin layer of unfed starter on a cloth or plate in a warm, dry location. Once completely dry and brittle, crumble into flakes and store in a paper envelope in a dry, cool location. Rehydrate with water when needed; allow 3–5 days of regular feeding to revive.
- Freezing: Active starter can be frozen for months. Thaw slowly; feed for 3 days to revive.
Sourdough Summary
Sourdough starter is a self-perpetuating culture of wild yeast and lactic acid bacteria that replaces commercial yeast entirely in bread production. It is started by mixing whole-grain flour and unchlorinated water and feeding daily for 7 days until actively rising and falling after each feeding. Maintenance requires only flour, water, and regular feeding — once weekly in a refrigerator, or daily at room temperature. Sourdough bread follows a process of autolyse, fermentation with folding, shaping, cold proofing, and high-heat baking. The result is a nutritionally superior bread (improved mineral bioavailability, extended shelf life, lower glycemic index) that requires no purchased inputs and can be produced indefinitely from any grain crop.