Loaf 12: starter instead of yeast
6 g of instant yeast out, 80 g of ripe starter in. The starter brings 40 g of flour and 40 g of water of its own, which is why added flour drops to 360 g and total hydration still reads 70%.
This is Loaf 12 of 16, and the one thing that changed from Loaf 11 is the leavening: 6 g of instant yeast out, 80 g of ripe 100% hydration sourdough starter in.
This is sourdough. You have arrived at it having changed one thing eleven times, which is why it is going to feel ordinary rather than mystical.
The frozen four, unmoved: 400 g flour, 8 g salt (2%), one 9 x 5 inch (23 x 13 cm) loaf pan, 375°F / 190°C.
The bookkeeping, which is the whole trick
The formula table below says 360 g of flour, not 400 g. Nothing has been broken. Here is the arithmetic, and once you have it you can read any sourdough formula in the world.
A 100% hydration starter is half flour and half water by weight. So 80 g of starter is 40 g of flour plus 40 g of water, already mixed and already fermenting.
That flour and water are part of the loaf. They are not an extra. So you subtract them from what you add:
- Added flour drops from 400 g to 360 g, because 40 g of flour walked in inside the starter. Total flour is still 400 g.
- Added water drops from 280 g to 240 g, because 40 g of water walked in the same way. Total water is still 280 g.
- Total hydration is still 70%, exactly as it was at Loaves 9, 10 and 11.
That is why the flour row reads 90% and the water row reads 60% while the loaf is a 70% hydration dough. Baker's percentage in this course is always a percentage of the 400 g of total flour, and the water row is added water only. Every sourdough recipe that confuses people is confusing them on precisely this point.
The formula
| Ingredient | Grams | Cups / spoons | Baker's % |
|---|---|---|---|
| All-purpose flour | 360 g | 3 cups | 90% |
| Water | 240 g | 1 cup + 1 tsp | 60% |
| Sourdough starter (100% hydration) | 80 g | ⅓ cup | 20% |
| Fine sea salt | 8 g | 1⅓ tsp | 2% |
Frozen: 400 g flour · 8 g salt (2%) · 9 × 5 in pan · 375°F / 190°C · Hydration: 70% (280 g water on 400 g flour)
The method
- Feed your starter and wait for it to peak, 4 to 6 hours at 75°F / 24°C.
- Mix the flour, water, salt and starter to no dry flour, about 2 minutes with a wet spoon.
- Three sets of folds in the first hour at 75°F / 24°C, as Loaf 10.
- Bulk at 75°F / 24°C until the gate, 5 to 6 hours. Sourdough is slower than yeast by a factor of about three.
- Shape, into the pan, cover, fridge at 38 to 40°F / 3 to 4°C for 12 to 16 hours.
- Bake from cold at 375°F / 190°C, 45 to 50 minutes.
- Cool 2 hours at room temperature.
Every step except the first is one you have already done. The only new instruction is "wait for the starter to peak", and the only new number is a bulk that runs three times as long at the same temperature.
Why this works
Commercial yeast is one organism doing one job very fast. Saccharomyces cerevisiae, selected for gas production, and that is all it gives you.
A starter is a mixed population of wild yeasts and lactic acid bacteria. The yeasts make the gas, as before, just more slowly and in fewer numbers, which is why the bulk goes from about 2 hours to 5 or 6 hours at the same 75°F / 24°C. The bacteria make lactic and acetic acid as they go.
That acid is the flavour, and it is what people are chasing when they say sourdough tastes better. It also acidifies the crumb, and an acidic crumb resists both mould and staling, which is why this loaf is still good on day three while Loaf 11 was best on day one.
You also stop keeping yeast in the house. The starter is yours, it renews itself on flour and water, and it does not run out.
How you know it's ready
Two gates now, and the first one is new.
The starter goes in only at peak. Doubled in the jar, domed on top, still rounded rather than sinking in the middle, and a spoonful floats in a glass of water. 4 to 6 hours after feeding at 75°F / 24°C is typical. A starter on the way up is not ready and a starter that has collapsed has already spent itself.
Then the bulk: risen by half to three quarters, domed, jiggly when you shake the bowl, bubbles visible where the dough meets the glass, at 75°F / 24°C. Not doubled. 5 to 6 hours is the usual span, and the look is the instruction. When you are unsure, it needs another hour.
Out of the fridge, the loaf reads the same as Loaf 11 did: risen to about ¾ inch / 2 cm below the rim. Bake until the centre reads 205 to 210°F / 96 to 99°C.
What goes wrong
The failure mode this loaf introduces: a dense, gummy loaf that barely rose.
One cause: the starter was not at peak when it went in. Either it was promoted to baking duty before it was mature, or it peaked and collapsed earlier in the day while you were busy.
Almost every dense first sourdough traces back to this and nothing else. Not the flour, not the hydration, not the shaping, not the oven. The float test takes ten seconds and it is the highest-value ten seconds in sourdough baking.
When it worked
A gentle tang, not a sharp one. A crust that browns deeper than Loaf 11 did. An open, slightly chewier crumb. A loaf that is still good on day three.
And no commercial yeast anywhere in the house.
Bake it twice successfully before moving on, because one good loaf is luck and two is a skill.
You baked Loaf 12. Did it work?
The course is free. This is the one thing it asks for. Thirty seconds, and it is how the next baker gets a better loaf.