BastienSourdough Starter
A sourdough starter is a live culture of wild yeast and lactic acid bacteria maintained with regular flour-and-water feedings — used to leaven bread, takes 7-14 days to create from scratch.
A sourdough starter is a living culture of wild yeast and lactic acid bacteria maintained with regular feedings of flour and water. Instead of commercial yeast, bakers use a sourdough starter to leaven bread, producing the tangy flavor, chewy crumb, and crisp crust that define sourdough baking. A portion of starter built up and ready to bake with is often called a levain.
Some starters have been kept alive for over a century, passed down through generations. The Boudin Bakery starter in San Francisco dates to 1849. I've maintained mine for about four years now. It's gone through neglect, fridge hibernation, and one accidental encounter with dish soap. It survived all of it.
How does a sourdough starter work?
When you mix flour and water and leave the mixture at room temperature, wild yeast and bacteria already present in the flour begin to colonize the mixture. Over 5-14 days of regular feedings, two groups of microorganisms establish a stable ecosystem:
Wild yeast (primarily Saccharomyces and Kazachstania species) produces carbon dioxide gas. This is what makes the dough rise.
Lactic acid bacteria (primarily Lactobacillus) produce lactic and acetic acids. These acids give sourdough its characteristic tang and also act as natural preservatives. Sourdough bread stays fresh longer than commercially yeasted bread because of them.
The two groups work together. The acids produced by bacteria create an environment too acidic for most competing organisms, while the yeast thrives in it. This symbiosis is why a healthy starter is stable and resistant to contamination.
How do you make a sourdough starter from scratch?
The sourdough starter ingredients are simple: flour and water. That's it. No commercial yeast, no sugar, no yogurt. The wild yeast and bacteria come from the flour itself and the air in your kitchen.
A few notes on the process. Days 2-4 often produce a burst of activity followed by a dead period. This is normal. The early bacteria that cause the initial bubbling get replaced by the lactic acid bacteria that will dominate long-term. Don't panic when it seems to "die" around day 3-5.
You can use all-purpose flour instead of whole wheat, but whole wheat gets things moving faster because it has more wild microorganisms and nutrients. I started my current starter on 100% rye for the first five days, then switched to a mix of 80% bread flour and 20% whole wheat. The rye kickstarted the fermentation noticeably.
How do you feed a sourdough starter?
Feeding means discarding part of the culture and adding fresh flour and water. This replenishes the food supply for the yeast and bacteria.
Standard feeding ratio: 1:1:1 by weight. Keep 50g of starter, add 50g flour and 50g water. Use a kitchen scale for accuracy. Volume measurements are too imprecise for consistent results.
Feeding schedule:
| Storage method | Feeding frequency | Best for |
|---|---|---|
| Room temperature (21-26°C / 70-78°F) | Once or twice daily | Active bakers who bake multiple times per week |
| Refrigerator (3-4°C / 38-40°F) | Once every 5-7 days | Occasional bakers who bake once a week or less |
Flour choice matters. Unbleached all-purpose or bread flour works well for maintenance. Whole wheat or rye flour accelerates fermentation because it contains more nutrients and wild microorganisms. Many bakers use a mix (80% white flour, 20% whole wheat) for a balance of activity and mild flavor.
What are the signs of a healthy sourdough starter?
It takes 7-14 days to establish a new sourdough starter from scratch, and another 2-4 weeks before it's strong enough to reliably leaven bread. Patience during this initial phase is the biggest factor in success.
What are the most common sourdough starter problems?
Most likely too cold or still too young. Move it to a warmer spot (24-27°C / 75-80°F). The top of your fridge, a turned-off oven with the light on, or near a radiator all work. If it's under two weeks old, keep feeding daily and wait.
Your starter is hungry. The food supply ran out. Pour off the hooch (or stir it back in for more tang), feed immediately, and increase your feeding frequency.
Severely underfed. Feed twice daily for 2-3 days until the smell shifts back to a pleasant sourness. Use warm water (around 27°C) to boost activity.
Over-ripe. It peaked before you caught it. Reduce the starter amount in your feeding (try a 1:2:2 ratio instead of 1:1:1) or use cooler water to slow things down.
Contamination by harmful bacteria or mold. Discard the entire starter and begin again. This is rare with a mature culture but can happen early on.
What is the difference between sourdough starter and commercial yeast?
Neither is "better." Commercial yeast is convenient and predictable. Sourdough rewards patience with flavor and texture you can't get any other way. Many bakers keep both in rotation.
What can you do with sourdough discard?
Every feeding produces discard: the portion of starter you remove before adding fresh flour and water. It doesn't have to be waste. Sourdough discard works in:
- Pancakes and waffles — adds tang and tenderness
- Crackers — thin, crisp, and deeply flavored
- Pizza dough — discard replaces some of the flour and water in a standard recipe
- Quick breads and muffins — adds complexity without long fermentation
- Flatbreads — naan, tortillas, and pita all benefit from discard
Discard doesn't have enough leavening power to rise bread on its own, but it adds flavor and acidity to anything that uses baking soda or baking powder as the primary leavener.
Sourdough starter in Fond
Fond's Bread Studio includes a sourdough starter tracker. Log each feeding, set reminders on your preferred schedule, and track your starter's rise-and-fall pattern over time. When you're ready to bake, Bread Studio calculates the right amount of starter for your recipe based on baker's percentages. You always know how much to pull and how much to keep.
