Converting High-Yeast 21g (3 Packets) Fresh Cake Yeast to Sourdough Levain in 500g Flour
High-inoculation conversion math comparing 100g direct yeast equivalency vs. 100g (20% baker's math) for 500g flour recipes.
If your goal is simply a sourdough version of a 500g recipe that used 21g of Fresh Cake Yeast, the simplest path is 20% inoculation: 100g of ripe levain, with 50g grain and 50g water removed from the main mix, leaving 450g and 300g. Expect 4.0 – 5.5 hours at 76°F (24°C) instead of a two-hour rise.
- Direct Yeast Equivalent
- 100g StarterDeduct 50g flour & 50g water
- 20% Artisan Inoculation
- 100g StarterDeduct 50g flour & 50g water
- Adjusted Main Flour/Water
- 450g / 300gPreserves 500g 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
Starter Deduction Grid for 21g (3 Packets) Fresh Cake Yeast in 500g Flour
Every figure is derived from the 500g flour / 350g liquid base formula and the 21g fresh cake yeast dose.
| Starter Hydration Level | Levain Required by Yeast Weight | Flour & Liquid Left in the Bowl | Levain Required at 20% Inoculation | Corrected Main Mix |
|---|---|---|---|---|
| 500g flour @ 50% [Primary] | 100g starter (66.7g F / 33.3g W) | 433.3g F / 316.7g W | 100g starter (66.7g F / 33.3g W) | 433.3g F / 316.7g W |
| 1000g flour @ 100% Low Hydration | 100g starter (50g F / 50g W) | 950g F / 650g W | 200g starter (100g F / 100g W) | 900g F / 600g W |
| 400g flour @ 125% Mid Hydration | 100g starter (44.4g F / 55.6g W) | 355.6g F / 224.4g W | 80g starter (35.6g F / 44.4g W) | 364.4g F / 235.6g W |
| 500g flour @ 75% High Hydration | 100g starter (57.1g F / 42.9g W) | 442.9g F / 307.1g W | 100g starter (57.1g F / 42.9g W) | 442.9g F / 307.1g W |
| 500g flour @ 100% Standard 100% | 100g starter (50g F / 50g W) | 450g F / 300g W | 100g starter (50g F / 50g W) | 450g F / 300g W |
On-Bench Hydration & Fermentation Adjuster
Modify base flour mass, levain inoculation, or ambient kitchen temperature below to recalculate from this 100g Starter baseline.
Balancing Osmotic Stress & Hydration When Replacing 21g Fresh Cake Yeast in 500g Flour
Because fresh cake yeast is a pure monoculture of Saccharomyces cerevisiae, transitioning your 500g batch to sourdough requires tracking volumetric aliquot rise (+50%) over 4.0 – 5.5 hours at 76°F (24°C) rather than watching a 60-minute clock.
If your original recipe used 21 grams of fresh cake yeast for a sweet or enriched dough, the 100g 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 (21g Fresh Cake Yeast → Sourdough in 500g Flour)
- Check the Starter Is Ripe: 100g of levain must be domed, bubbly and at full stretch; a flat starter slows the 4.0 – 5.5 hours at 76°F (24°C) window significantly.
- Combine 500g of Flour with the Adjusted Liquid: Pour 300g, saving 10% to dissolve the salt later.
- Fold in 100g Starter and 2% Salt: Add the levain, pinch through the dough, and work in the salt water.
- Ferment to +50%: Judge by volume in a straight-sided jar, then shape, retard overnight and bake on a preheated stone or in a Dutch oven.
Common Scaling & Troubleshooting Questions (100g Starter)
Is a 500g sourdough conversion suitable for a pizza or focaccia base?
Yes, and long cold retarding is often an advantage for pizza. Mix 100g of levain into 450g grain and 300g water and refrigerate 24–48 hours.
What happens to my hydration when I swap 21g fresh cake yeast for sourdough culture?
Nothing, if you deduct correctly. 100g of sourdough culture carries 50g flour and 50g water, so removing both keeps the 500g dough at 70% true hydration.
Can I convert a 500g dough that already contains a preferment or poolish?
Yes, but dissolve the preferment's yeast into the main mix first so the full 21g of leavening power is counted. Then deduct 50g grain and 50g water for the levain you are adding.