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).
I never punch down a dough. I often letter fold the dough. Hammelman's book is probably the best on that technical aspect of baking. But some breads actually involve doughs that are kneaded a second time--as I recall the Mantovano in Marcella Hazan's classic Italian book. In any case, my understanding is that these techniques are aimed at primarily degassing the dough, since CO2 is a waste product so the yeast can continue to do their thing. The folding also strengthens gluten and redistributes the dough, evening out temperature and fermentation rate differences.
I agree with smtucker that "punch down" is a really unfortunate phrase--the dough needs a gentle de-gassing to eliminate large CO2 pockets that can delay fermentation, and folding instead of punching stretches, realigns, and strengthens the gluten, to create a strong rise and oven spring (Hamelman). Reinhardt's letter fold works beautifully for focaccia and ciabatta (ever try punching down ciabatta dough? hehehehe), and also for sturdier, less hydrated doughs. Cowboyardee, I'd vote for folding, not punching. See what your results are....
The reason to "punch down" the dough is to give the bread an extra dimension in taste (and sometimes texture). Punching down the dough frees up more food for the yeast. The longer the yeast feeds, the more complex the flavor of the loaf.
However, like all things, there can too many "punching down" cycles. Too many rises can result in off flavors, such as bitterness and a beery flavor, to occur in your bread. As well as carbon dioxide yeast releases alcohol and acids. Too much acid in your loaf can actually cause the yeast to die off.
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.
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!
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?
As a home baker, the reason I know for punching down the dough is to vent frustrations brought on by management. lol
Seriously, the punching down redistributes the pockets evenly and makes for easier shaping. The second rise will give the extra lift. (From Alton Brown? Don't remember.)