How to Convert 80g Stiff Sourdough Starter (50% Hydration) to Commercial Yeast
Restoring +53.3g flour and +26.7g water when replacing 80g of 50% stiff levain with dry or fresh yeast.
Why bother converting back at all? Three reasons. You need a predictable two-hour rise for a schedule; you want the cleaner flavour of a commercial-yeast crumb; or you have 80g of starter in the jar you would rather not waste. The cost is that you lose the acid complexity, so season the batch with the recipe's own aromatics.
- Add Back Flour
- +53.3gReplaces flour inside 80g (50%) starter
- Add Back Water
- +26.7gReplaces water inside 80g (50%) starter
- Instant Yeast (2-Hr Rise)
- 7g (2.3 tsp)For 503.3g total flour batch
- Preserved Hydration
- 67.9%341.7g W / 503.3g F
Instant, Active Dry & Fresh Yeast for 80g of 50% Starter
Calculated on a 450g main flour + 53.3g restored starter flour (503.3g total flour) batch.
| Target Fermentation Schedule | Instant Dry Yeast (IDY) | Active Dry Yeast (ADY) | Fresh Compressed Yeast | Required Dough Restoration |
|---|---|---|---|---|
| 80g 50% starter — Standard Same-Day (1.5–2 hrs) [Baseline] | use 7g instant | use 8.8g active dry | use 21.1g fresh | add 53.3g flour + 26.7g water |
| 90g 50% starter — Slow Artisan Bulk (3.5–4.5 hrs) Smaller Batch | use 3.6g instant | use 4.5g active dry | use 10.7g fresh | add 60g flour + 30g water |
| 70g 50% starter — Overnight No-Knead / Cold Proof (12–18 hrs) Larger Batch | use 1.2g instant | use 1.6g active dry | use 3.7g fresh | add 46.7g flour + 23.3g water |
| 100g 50% starter — Standard Same-Day (1.5–2 hrs) Half Size | use 7.2g instant | use 9g active dry | use 21.7g fresh | add 66.7g flour + 33.3g water |
| 60g 50% starter — Slow Artisan Bulk (3.5–4.5 hrs) Double Size | use 3.4g instant | use 4.3g active dry | use 10.3g fresh | add 40g flour + 20g water |
Dynamic Stoichiometric Workbench (+53.3g)
Test custom loaf weights or alternative fermentation schedules directly against the +26.7g benchmark above.
Decomposing 80g of 50% Stiff Levain: High-Flour Mass Conservation
A cold overnight ferment changes the yeast arithmetic entirely. The 7g that produces a 1.5 – 2.0 hours warm bulk rise would be a violent over-proof at 39°F (4°C), so the overnight schedule needs roughly a fifth of the instant-yeast dose for the same 503.3g of flour.
A practical test of a successful conversion: the dough should feel smooth rather than tacky after mixing, hold a windowpane, and reach the same volume in the oven as the original levain dough even though it got there in a fraction of the time.
Step-by-Step Reverse Conversion Protocol (80g @ 50%)
- Audit the Original Formula: Confirm the formula's yeast was the only leavening, and that the 80g of 50% starter was the sole source of the 53.3g of hidden flour.
- Rebuild at Full Scale: The dough is now 503.3g flour and 341.7g liquid — the same numbers as before, minus the starter.
- Dose for the Schedule You Want: 7g (2.3 tsp) of instant yeast for a 1.5 – 2.0 hours warm bulk rise; use about a fifth of that for a cold overnight ferment.
- Bake and Compare: The crumb will be lighter and less acid-forward, but the volume and crust colour should be close to the levain original.
Key Baker's Math Questions (Add Back Flour: +53.3g)
Will my converted dough taste different from the levain version?
Yes. The roughly 2g of residual acid inside 80 grams of starter was providing both flavour and tenderising, and commercial yeast replaces neither.
Can I convert a stiff 50% levain to yeast?
Yes, and the deduction is larger on the flour side: 80g at 50% hydration holds 53g flour and 27g water rather than the 53.3g / 26.7g of a 50% starter.
How much flour and water are inside 80g of 50% hydration starter?
80g of 50% hydration sourdough starter contains 53.3g flour and 26.7g water.