Convert 7g (1 Packet / 2¼ tsp) Fresh Cake Yeast to Sourdough Starter (500g Flour Recipe)
Zero-drift flour and liquid deduction math for converting 7g of fresh cake yeast into 50%–125% hydration sourdough levain on a 500g base.
If your goal is simply a sourdough version of a 500g recipe that used 7g of Fresh Cake Yeast, the simplest path is 20% inoculation: 100g of ripe sourdough culture, with 50g flour 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
- 33.3g StarterDeduct 16.7g flour & 16.7g 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 7g (1 Packet / 2¼ tsp) Fresh Cake Yeast in 500g Flour
Compare the packet-equivalency column against the 20% baker's math column to see how much the two conventions diverge on a 500g base.
| Starter Hydration Level | Levain Required by Yeast Weight | Flour & Liquid Left in the Bowl | Levain Required at 20% Inoculation | Corrected Main Mix |
|---|---|---|---|---|
| 400g flour @ 100% [Exact Target] | 33.3g starter (16.7g F / 16.7g W) | 383.3g F / 263.3g W | 80g starter (40g F / 40g W) | 360g F / 240g W |
| 500g flour @ 125% Alt Row A | 33.3g starter (14.8g F / 18.5g W) | 485.2g F / 331.5g W | 100g starter (44.4g F / 55.6g W) | 455.6g F / 294.4g W |
| 500g flour @ 50% Alt Row B | 33.3g starter (22.2g F / 11.1g W) | 477.8g F / 338.9g W | 100g starter (66.7g F / 33.3g W) | 433.3g F / 316.7g W |
| 1000g flour @ 100% Alt Row C | 33.3g starter (16.7g F / 16.7g W) | 983.3g F / 683.3g W | 200g starter (100g F / 100g W) | 900g F / 600g W |
| 500g flour @ 75% Alt Row D | 33.3g starter (19g F / 14.3g W) | 481g F / 335.7g W | 100g starter (57.1g F / 42.9g W) | 442.9g F / 307.1g W |
On-Bench Hydration & Fermentation Adjuster
Modify base flour mass, levain inoculation, or ambient kitchen temperature below to recalculate from this 33.3g Starter baseline.
Why 7g Fresh Cake Yeast Cannot Be Swapped in 500g Flour Without Deducting Starter Water
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.
Direct packet scaling of 7g (1 Packet / 2¼ tsp) Fresh Cake Yeast maps to 33.3g starter (-16.7g flour / -16.7g water), while artisan baker's math standardises inoculation at 20% of 500g (100g starter, leaving 450g main flour and 300g liquid).
3-Step Conversion Checklist (7g Fresh Cake Yeast → Sourdough in 500g Flour)
- Weigh Active Levain (100g or 33.3g): Measure 100g peaked 100% starter for 20% inoculation, or 33.3g for direct 7g Fresh Cake Yeast equivalency.
- Deduct Main Flour & Liquid (500g Base): Scale main flour to 450g (-50g) and liquid to 300g (-50g).
- Ferment for 4.0 – 5.5 hours at 76°F (24°C): Hold the 500g dough at 75°F–78°F until +50% volumetric expansion before shaping and cold proofing.
- Retard and Bake: Cold-proof the shaped dough for 12–16 hours at 38°F, then bake covered and uncover to a deep mahogany crust.
Common Scaling & Troubleshooting Questions (33.3g Starter)
How much flour and water do I subtract when adding 100g starter to 500g flour?
At 100% starter hydration, subtract 50g flour and 50g water/milk from your 500g flour recipe (leaving 450g flour and 300g liquid).
Can I halve the recipe and still use 7 g of Fresh Cake Yeast?
You can, but the effective inoculation doubles, so 33.3g of levain on half the flour ferments faster than the original. Plan for a shorter bulk.
Should I use 33.3g or 100g of culture?
Use 33.3g if you want to preserve the exact leavening power of 7g fresh cake yeast. Use 100g if you want standard 20% artisan inoculation regardless of the original yeast weight.