What Is Crumb Structure?
The Definition
Crumb Structure refers to the pattern of holes (alveoli) inside the bread. It is the primary diagnostic tool for a baker. A "tight" crumb with small, even holes often indicates lower hydration or over-handling. An "open" crumb with large, irregular holes indicates high hydration and gentle fermentation.
The Science: Gas vs. Strength
The crumb is a fossilized record of two competing forces:
Gas Production (Expansion): Yeast produces CO₂, blowing bubbles in the dough.
Gluten Strength (Retention): The protein network traps that gas. If the gluten is too tight, the bubbles stay small. If the gluten is degraded (over-proofed), the bubbles pop and collapse.
The Diagnostic Spectrum
Not all holes are created equal. Here is how to read your crumb:
1. The "Wild" / Open Crumb
Description: Large, irregular holes dispersed evenly throughout the loaf. The cell walls are thin and glossy (gelatinized).
The Cause: High hydration (75%+), strong gluten development, and perfect fermentation timing.
The Fix: None. This is the goal for artisan sourdough.
2. The "Fool's Crumb" (The Imposter)
Description: Giant caverns or tunnels (often near the top crust) surrounded by dense, gummy, hole-free dough at the bottom.
The Diagnosis: Under-fermentation. The yeast produced gas, but the gluten structure wasn't relaxed enough to expand evenly, or the bulk fermentation was cut short, leaving the dough "young."
The Fix: Extend your Bulk Fermentation by 30–60 minutes. Do not confuse large tunneling for an "open crumb."
3. The "Sandwich" / Uniform Crumb
Description: Small, evenly distributed holes (like a sponge). The texture is soft and fluffy.
The Diagnosis: Low Hydration or Intensive Degassing. This occurs with lower water content (60–65%) or when the dough is kneaded aggressively/rolled tightly, forcing large gas bubbles out.
The Fix: If this was unintentional, increase hydration by 5–10% and handle the dough more gently during shaping.
4. The "Flying Crust" / Collapsed Crumb
Description: The crust separates from the crumb, creating a large gap at the top, while the crumb below is dense or collapsed.
The Diagnosis: Over-proofing. The gluten network degraded to the point where it could no longer hold the gas structure. When the heat hit, the structure collapsed internally while the crust set.
The Fix: Reduce bulk fermentation time or get the dough into the fridge (retard) sooner.
5. The "Dense Brick"
Description: Heavy, gummy, almost no visible holes.
The Diagnosis: Inactive Starter. Your culture did not have the population density to raise the dough.
The Fix: Refresh your starter. Ensure it triples in volume within 4–6 hours before using it.
Last updated: 6 January, 2026
Pre-shaping is an intermediate step between bulk fermentation and final shaping. The dough is divided and loosely formed into rounds, then left to rest (bench rest) for 15–30 minutes. This step reorganises the gluten network after the division and creates a smooth "skin" on the dough.