From dictionary.com
crumb:
[kruhm] noun
the soft inner portion of a bread (distinguished from crust ).
In his book 52 Loaves William Alexander was nearly obsessed with producing a bread that yielded a holey interior. I wasn’t sure why the crumb was so important to him so I did a little research to find out what made those uneven holes so desirable.
A holey crumb indicates the proper amount of kneading, likely by hand incorporating stretching and folding. It is a sign that the starter was lively, and that the baker added steam to the baking process. Properly hydrated dough increases holes during the baking. Those irregular holes throughout the crumb are visual cues that the bread is well made. In short, it is not the holes so much as what they mean that matters.
My first loaf made with the wild yeast starter I had made from scratch was kneaded in the mixer with a bread hook. The dough had a lot of body. At the time, I felt like the crumb was adequate.
The second time I tried the recipe I gave in to my friend Michael’s admonition to put the mixer away and get my hands into the dough. I did the stretch and fold method. And for some reason my dough remained much more fluid throughout the process. The resulting loaf had a crumb I could be proud of.
I originally used the mixture because I feared mixing by hand would be too messy, time consuming and difficult. I was pleasantly surprised to find it was none of these things. Instead it was oddly therapeutic. It is kinetically soothing; in its smooth repetition and rhythm, the mind becomes free to wander. Cheaper than therapy, plus you have a delicious loaf of warm bread at the end.