Convert 40g Sourdough Starter (100% Hydration) to Commercial Yeast
How to remove 40g of 100% hydration levain from any sourdough recipe by restoring +20g flour and +20g water.
A 100% hydration starter is half flour and half water by weight, so 40g of it hides 20g of flour and 20g of water. Deleting it without restoring both shrinks the loaf and skews the ratio away from 71.3%. Restoring them and dosing 6.6g of yeast keeps the dough identical.
- Add Back Flour
- +20gReplaces flour inside 40g (100%) starter
- Add Back Water
- +20gReplaces water inside 40g (100%) starter
- Instant Yeast (2-Hr Rise)
- 6.6g (2.1 tsp)For 470g total flour batch
- Preserved Hydration
- 71.3%335g W / 470g F
Reverse Conversion Chart: 40g Starter → Commercial Yeast
The restoration column shows the flour and water that must go back into the main mix to keep the 71.3% hydration intact.
| Proofing Plan | Instant Dry Yeast | Active Dry Yeast | Fresh Compressed Yeast | Dough Restoration |
|---|---|---|---|---|
| Line 20g / 100% [Exact Target] | 6.4g IDY (2.1 tsp) | 8.1g ADY (2.6 tsp) | 19.3g cake yeast | 1.5 – 2.0 hours warm bulk rise |
| Line 40g / 100% Alt Row A | 3.3g IDY (1.1 tsp) | 4.1g ADY (1.3 tsp) | 9.9g cake yeast | 3.5 – 4.5 hours slow room-temp rise |
| Line 60g / 100% Alt Row B | 1.2g IDY (0.4 tsp) | 1.5g ADY (0.5 tsp) | 3.6g cake yeast | 12 – 18 hours cold fermentation (39°F / 4°C) |
| Line 30g / 100% Alt Row C | 6.5g IDY (2.1 tsp) | 8.1g ADY (2.6 tsp) | 19.5g cake yeast | 1.5 – 2.0 hours warm bulk rise |
| Line 50g / 100% Alt Row D | 3.3g IDY (1.1 tsp) | 4.2g ADY (1.3 tsp) | 10g cake yeast | 3.5 – 4.5 hours slow room-temp rise |
On-Bench Hydration & Fermentation Adjuster
Modify base flour mass, levain inoculation, or ambient kitchen temperature below to recalculate from this +20g baseline.
Decomposing 40g of 100% Hydration Starter: Flour + Water Conservation
Water temperature becomes more critical once wild yeast is out of the equation. Commercial Saccharomyces cerevisiae tolerates a wider range than a mixed levain culture, but a direct 6.6g dose still prefers water around 100°F (38°C) for a 1.5 – 2.0 hours warm bulk rise.
Watch the oven spring rather than the mixing. With 6.6g of commercial yeast the loaf will rise fast in the first 90 minutes, which means less time to develop a rounded shape and more chance of a flat crown if you shape too early.
Step-by-Step Reverse Conversion Protocol (40g @ 100%)
- Plan Around the Lost Complexity: Without a levain you lose the slow acid build, so if the 40g of 100% starter was there for flavour, add a little honey or malt and a spoonful of yoghurt.
- Restore the Mass: Return 20g of grain and 20g of water to the base recipe.
- Dose the Yeast: 6.6g (2.1 tsp) of instant, 8.3g of active dry, or 19.8g of fresh cake yeast.
- Ferment, Shape, Bake: Respect the 1.5 – 2.0 hours warm bulk rise schedule, and remember the 71.3% hydration is unchanged by the swap.
Common Scaling & Troubleshooting Questions (+20g)
How long should the converted dough bulk for at room temperature?
Plan on 1.5 – 2.0 hours warm bulk rise, then shape and bake immediately. There is no levain to justify a long slow bulk, and a commercial-yeast dough left longer simply over-proofs.
Can I convert a batch that also contains a poolish or preferment?
Yes, but count the preferment's yeast separately and subtract it from the 6.6g, otherwise the 470g batch will over-proof.
Can I use fresh cake yeast instead of dry yeast for the 40g starter swap?
Yes, but fresh compressed yeast is only about a third as potent per gram, so you need roughly 19.8g instead of 6.6g.