Punching down dough - why?
Right off the bat - I'm an embarrassingly bad baker. I have a hard time following a recipe without understanding exactly why I'm doing what I'm doing.
So one little question that's been nagging me: what does punching down dough after the first rise accomplish? What is the exact difference to the end product from if you hadn't punched down the dough?
It would seem that you're letting gasses out of the dough, which one would think would lead to a denser bread. But I see it in recipes to make very light airy breads frequently. It's not that I'm doubting centuries of technique. I just want to know what is physically happening and why some dough recipes ask that you punch down the dough while others do not. McGee has failed me on this one (or else just hid the explanation well).
Thanks for the answers, all. So it seems that punching down the dough leads to smaller and more even air bubbles within the dough, though not necessarily denser dough, and makes it easier to form the dough to portions. Possibly also more yeast action/fermentation. And it's also great fun.
Sound about right?
Punching down the dough is a really bad phrase since it doesn't describe the process well at all. Punching does nothing good for your dough. Instead, as you remove the dough from the first rising bowl you should gently massage the dough to redistribute the yeast bubbles and to make them smaller.
Do I fully understand the science? Nope. But I trust Peter Reinhardt and that is what he says!
I don't buy the "redistribute air bubbles" theory. I find it difficult to believe that folding the dough a couple of time will redistribute its internals. I have also found that no matter how rough or casual I am in handling the dough, it always rises sufficiently (the proverbial "double in volume") in the last rise, so "defalting the dough" has not been a concern of mine.
I subscribe more to the "redistribute yeast/food supply" theory of "punching down dough". I "punch down" my 48-hour pre-ferment two or three times by kneading it a couple of times each time. I kinda suspect that, since yeast don't have legs :) , after they have "digested" the starch in their immediate vicinity, "punching down" shift the dough around just enough so yeast cells come into contact with more starch.