Crumb

Crumb refers to the interior of a sliced loaf, as opposed to the crust on the outside. Bakers describe crumb in terms of how open or tight it is: an open crumb has larger, irregular holes and a glossy, almost translucent look between them, while a tight crumb has smaller, more even holes and a denser overall feel.

The crumb you get is shaped by several things working together, including hydration, how much strength was built during mixing and folding, how long the dough fermented, and how gently it was shaped without knocking out too much gas. Higher hydration doughs generally trend toward a more open crumb, but only if fermentation and shaping are also well judged, which is why crumb is often used to read back what happened earlier in the bake.

A sharp bread knife makes it much easier to see true crumb structure without tearing or compressing the slice as you cut. A common mistake is chasing an extremely open crumb before other fundamentals are solid, since a wildly open crumb from under-development or over-proofing often comes with poor eating quality and structural weakness. A slightly tighter, evenly holed crumb from a well-fermented dough is usually a better sign of skill than an inconsistent, tunnel-filled one.