I just made pita bread and had to knead it for 10 minutes then let it sit 10 minutes. When I came back to it after those 10 minutes it was all pillowy and soft. I’m curious what’s happening on a molecular level while kneading to make this happen.
In: Chemistry
Kneading dough with wheat flour in it helps it develop gluten, which is the protein that makes the dough more stretchy and sproingy.
Your yeast, meanwhile, is breaking down the wheat a little into sugars that it’ll use to grow, and CO2, which it spits out. That CO2 is what makes the bubbles in your bread.
If you don’t knead enough, there isn’t enough gluten formation to hold in all this CO2 that make those cool pockets. It can lead to thick, dense bread with no bubbles.
Someone will likely come in with a much better explanation. But, my understanding is that you are exposing the yeast to more food. During the initial rise, they eat what surrounds them, then when kneading again it moves things around to provide more food.
I’m not a baker, so this is probably grossly oversimplified, but two things come to mind.
First, kneading wheat flour and water together produces gluten. Gluten is a tough protein that enables doughs to be all stretchy without breaking.
Second, kneading with the yeast distributes the yeast throughout the dough. The yeast then consume sugars present in the dough (that you probably added as part of the recipe), producing alcohol and carbon dioxide. The carbon dioxide then forms little pockets trapped by the gluten, leavening the dough.
So, in that short a period, what you’re seeing is more about what gets called “gluten development,” and it’s more about the wheat proteins than anything the yeast is doing.
Imagine gluten is like stretchy Velcro bits. It sticks best when it’s a bit wet, and if it sticks to itself it doesn’t like to stick to other stuff.
So as you knead it, you’re doing two things. First your touching the gluten molecules to other gluten molecules, which slowly turn into long chains and nets. If you’ve ever seen the spiderweb looking stuff when you stretch out dough, those strings are literally the gluten chains. The other thing you’re doing is stretching those chains out like rubber bands. Some of them will even break as you stretch them too far.
So as soon as you stop kneading, the dough can relax as the strings of gluten pull in on themselves. That slow shifting lets broken ends reform, and it introduces the gluten to more gluten that might not be attached.
So it’s softer because it’s loose, and smoother because it’s not broken.
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