Biga/Poolish/Pate Fermentee - why knead?
Reading Reinhart BBA etc. regarding Biga and Pate Fermentee (not so much Poolish) I noticed that the preparation of these preferments involve kneading and proofing much the same as you would for any final dough.
Since I presume neither gluten nor trapping carbon dioxide, bulk/volume are major concerns for a preferment, why are these stages of kneading, proofing and degassing necessary in a preferment? Is this something I also need to do with poolish? (I don't think I've ever successfully had a poolish 'double in volume' btw).
Actually perhaps a bigger question: why use a preferment at all? I'm not sure I follow the logic. How does it improve flavour (if one presumes flavour comes from extracting all we can from the flour), if the bulk of the flour used in the final dough has yet to be added?