The Science Behind the Perfect Crumb

What separates an average loaf from an exceptional one? The answer lies in the bubbles — the crumb. If you’ve ever seen perfect bread with irregular, glossy holes, you know what I mean.

What happens during fermentation?

Wild yeasts and lactic acid bacteria consume sugars in the flour and produce CO₂ and acids. The CO₂ creates bubbles; the acids give sourdough its characteristic flavour.

A good loaf is a conversation between time, temperature, and patience. — Chad Robertson

The role of gluten

Gluten is the network that traps bubbles. Without strong gluten, every bubble escapes — with too much, the bread becomes tough. Finding the right balance is the art.

Temperature is everything

At 24°C, yeasts are most active. At 4°C in the fridge they work slowly — but lactic acid bacteria produce more flavour. That’s why long cold proofing works so well.

Practical tips

For an open crumb: higher hydration (75–80%), gentle shaping, longer cold proof. For an even crumb: lower hydration (65–70%), tighter shaping, shorter proof.