The yeast has already produced plenty of gas during the first rise, and shaping knocks most of it out. Doing that on purpose and then waiting again looks like undoing an hour of work.
What does the second rise achieve that the first did not?
Accepted Answer
The two rises do different jobs, and knocking back is deliberate rather than an unfortunate side effect of shaping.
The first rise is mostly about flavour and structure. Yeast produces carbon dioxide, but also alcohols and organic acids, and the gluten network develops as the dough stretches around expanding bubbles.
Degassing then does three useful things: it redistributes the yeast into fresh sugar, evens out bubble sizes so the crumb is regular rather than a few large holes, and releases carbon dioxide that inhibits the yeast as it accumulates.
The second rise is the one that sets the final crumb, in the shape the loaf will keep. Skip it and you get a dense loaf with a coarse, uneven interior.
One thing worth correcting, because "leave it until doubled" is repeated everywhere and is the main cause of collapsed loaves.
Doubling is a rough guide for the first rise and a bad one for the second. Overproofed dough has stretched its gluten past the point where it can hold, and it collapses in the oven instead of springing.
The poke test is the reliable version: press a floured finger about a centimetre in. Springs back fully, needs longer. Springs back slowly leaving a slight dent, ready. Stays fully dented, overproofed.
Temperature is the variable most recipes hide. A rise time written for a warm kitchen means something quite different in a cold one, which is why timings vary so much between people following the same recipe.
The discussion on each answer is open to members.
Join free to read the rest