In some way or another you’ve probably heard about gluten before. Gluten is the protein that forms from glutenin and gliadin when flour is hydrated. Except that if you just wet your dough the strands of gluten will exist as a tangled mess. So what to do? Knead! As you knead dough the gluten strands straighten themselves out and create a complex structure within the dough. It is this structure that allows the bread to support itself as it rises. No structure and your dough will be likely to collapse in on itself.
How much kneading is necessary?
Many basic doughs will have to be kneaded for 10-12 minutes by hand, or 5-7 minutes with a stand mixer (though each recipe will specify). Even if you do have a stand mixer I recommend kneading by hand a few times to get a good feeling for how dough develops and what it feels like when it is ready to rise.
What starts out as a coarse and tough ball transforms into a smooth finished product. When kneaded sufficiently you will have an elastic dough that can pass the windowpane test. This means that you can stretch a piece of dough (without breaking) thin enough to see light through it without it breaking. Essentially, your dough should be flexible, elastic, and hold its shape (because it means you have strong gluten networks).
You’ll quickly know if you have not kneaded your dough enough when you bake it. As the gas built up by yeast bakes out of the bread the loaf will collapse if the gluten network isn’t strong enough to support the bread.
What about no-knead recipes?
No-knead bread recipes have gotten a lot of people involved in bread baking, which I think is great. Radically simple, there are other complex doughs (such as Tartine’s country bread) that utilize this technique.
Jim Lahey’s no-knead recipe dictates that you mix your dough and then cover it. And walk away! Then come back in 12-24 hours, how easy is that?! Even though you don’t do any kneading, the yeast does. Over the several hours you let the dough sit the yeasts release carbon dioxide, which move around the proteins in the bread and form a similar matrix that would happen if you kneaded the dough. Serious Eats has a pretty cool series of time lapse photos that demonstrate how this happens. So instead of kneading the dough over the course of 10 minutes it happens over several hours.
Chad Robertson’s Tartine country bread uses a series of dough turns throughout the rising process to speed up what happens in Lahey’s recipe.