Help me understand "builds".
Peter Reinhart touched on this briefly in The Bread Baker's Apprentice, but did not elaborate.
I am working on a sourdough recipe. I want a 350 gram leaven in the final dough, so I am starting with 50 grams of 100% starter.
If I understand the meaning, my leaven has three builds with a fourth when added to the final dough, as follows:
First build: 50 grams of starter, plus 15 grams of flour to bring it to 60% hydration. Ferment overnight at room temp.
Second build: 100 grams flour plus 59 grams water, and ferment again at room temp.
Third build: 70 grams of flour plus 56 grams of water and ferment.
The final build will be adding it to the final dough. This, to me, seems what is meant by "build". Is this correct, and if so, what purpose is there in doing this as opposed to just adding the correct amount of flour and water to bring it to 350 grams and letting it ferment?