How to Replace 2g (⅔ tsp) Fresh Cake Yeast with Sourdough Starter in a 400g Flour Recipe
Zero-drift flour and water deduction guide for converting low-yeast (2g fresh cake yeast) artisan or poolish doughs into 80g sourdough levain.
None of the arithmetic changes with the yeast brand, but the type does: fresh cake yeast carries its own potency per gram, so 2g of it converts to 9.5g of culture rather than the 80g that 20% baker's math prescribes. Either way, deduct the hidden flour and water — 4.8g and 4.8g in packet mode — or the 400g dough will not hold 70% hydration.
- Direct Yeast Equivalent
- 9.5g StarterDeduct 4.8g flour & 4.8g water
- 20% Artisan Inoculation
- 80g StarterDeduct 40g flour & 40g water
- Adjusted Main Flour/Water
- 360g / 240gPreserves 400g total system flour at 20% levain
- Sourdough Bulk Window
- 4.0 – 5.5 hoursAt 76°F (24°C) vs. 1–1.5 hrs for commercial yeast
Gram Weights for 400g Flour Sourdough Built from 2g Fresh Cake Yeast
Exact starter weights and main dough flour/water deductions for 2g Fresh Cake Yeast in 400g flour so True Total Hydration never drifts.
| Starter Water Ratio | Starter Weight & Hidden Flour/Water | Corrected Flour / Corrected Liquid | 20% Inoculation Weight | Corrected Flour / Corrected Liquid |
|---|---|---|---|---|
| Line 400g at 125% [Your Formula] | packet 9.5g (deduct 4.2g/5.3g) | remaining 395.8g + 274.7g | artisan 80g (deduct 35.6g/44.4g) | remaining 364.4g + 235.6g |
| Line 400g at 75% Leaner Dough | packet 9.5g (deduct 5.4g/4.1g) | remaining 394.6g + 275.9g | artisan 80g (deduct 45.7g/34.3g) | remaining 354.3g + 245.7g |
| Line 500g at 100% Wetter Dough | packet 9.5g (deduct 4.8g/4.8g) | remaining 495.2g + 345.2g | artisan 100g (deduct 50g/50g) | remaining 450g + 300g |
| Line 1000g at 100% Tighter Dough | packet 9.5g (deduct 4.8g/4.8g) | remaining 995.2g + 695.2g | artisan 200g (deduct 100g/100g) | remaining 900g + 600g |
| Line 400g at 50% Looser Dough | packet 9.5g (deduct 6.3g/3.2g) | remaining 393.7g + 276.8g | artisan 80g (deduct 53.3g/26.7g) | remaining 346.7g + 253.3g |
Dynamic Stoichiometric Workbench (9.5g Starter)
Test custom loaf weights or alternative fermentation schedules directly against the 80g Starter benchmark above.
Replacing Low-Inoculation 2g Fresh Cake Yeast in 400g Flour Without Shifting Hydration
Scaling the conversion is linear in the grain but not in the yeast. Doubling a 400g base to 800g while keeping 2g of Fresh Cake Yeast halves the effective inoculation, so 9.5g of levain is a far gentler ferment than 19g would be.
If your original recipe used 2g of fresh cake commercial yeast for a sweet or enriched dough, the 9.5g levain version usually needs its sugar reduced slightly, because the longer fermentation converts more of it and the finished crumb sweetens on its own.
3-Step Conversion Checklist (2g Fresh Cake Yeast → Sourdough in 400g Flour)
- Autolyse First: Combine 360g flour with 240g water (holding back 10% for salt) and rest 45 minutes.
- Add 80g of Ripe Levain: Pinch in the starter, add 2% salt with the reserved water, and mix until the dough is cohesive.
- Four Folds: Space two stretch and folds and two coil folds 30 minutes apart to build gluten without tearing the gas cells.
- Bulk, Shape and Retard: Reach the target rise, shape, and refrigerate 12–16 hours at 38°F before the final bake.
Key Baker's Math Questions (Direct Yeast Equivalent: 9.5g Starter)
Why does my converted 400g dough feel stickier than the original?
Almost always the 4.8g of hidden starter water was not deducted. Correct the liquid to 275.2 grams and the dough will tighten immediately.
Will my 400g sourdough version rise the same way as the 2g fresh cake yeast original?
No. Sourdough produces gas more slowly and with different gas retention, so judge the converted dough by +50% volumetric rise in a straight-sided jar rather than by doubling in a bowl.
How much grain and water do I subtract when adding 80g starter to 400g grain?
At 100% starter hydration, subtract 40g grain and 40g water/milk from your 400g grain recipe (leaving 360g grain and 240g liquid).