So I'm making the Pain de Campagne from BBA, which needs a pate fermentee. I prepared it yesterday evening, and instead of fermenting it for the indicated 1 hour (1.5 times size increase) I by accident left it for about 2.5 hours, so it more than doubled. Deflated and put it in the fridge (per instructions). This morning, as I also had seen before, it still rose some in the fridge. This got me wondering: Is it possible to overproof a pate fermentee? I have read a biga and poolish have an optimum ripeness and I understand that leaving a pate fermentee for really too long can be detrimental (depending on the amount of yeast of course), but what are the margins? Since in this formula 50% is in the preferment, I guess it has to still have some 'potential' when using it in the final dough, right?
The pate fermentee--or in English "Old dough"--is used primarily to condition the new dough to give it a distinctive leg-up on maturation and flavor compared to a bread made without it. Leavening is assured in Reinhart's Pain de Campagne by the addition of instant yeast in the BBA formula.
If you haven't yet read it all scan page 105 in BBA. Frankly, I don't give Reinhart high marks, but it does provide the beginning of understanding pre-ferments. You'll note on p105 he states pate fermentee will last in the refrigerator 3 days, and can also be frozen.
You might also be interested in this post
http://www.thefreshloaf.com/node/32383/old-dough-vs-natural-levain
scan the comments, especially ananda's remarks. (Andy) is a professional English baker, and former baking instructor. He provides some clear insights. You'll note I used the "old dough" as a leavening agent too, but that's not its purpose in modern baking.
David G