Preferments and ripeness.
Biga, pâte fermentée, poolish, etc., preferments all.
All have different points at which they are considered "ripe" or most-suited for use in (usually) a final dough.
I'm having trouble understanding how this ripeness point is derived?
If you change the seed quantity (up or down) and temperature (up or down), the ripeness point comes sooner or later. Yes. So, is "ripe" a derivation of yeast quantity per mass? Or is it just some woo-woo empirical notion that says "When it looks like this, it's ideal!"). If not, how is it derived? Yeast growth curve?
Also, what of extended prefermentation? If the result of prefermentation is increased acidity, esters, and other organics, why be concerned with ripeness at all? Why not just let the preferment proceed until it can't ferment anymore? Too much acidity, which strengthens gluten, so we don't want to push acid development too far, else shaping, spring, and eating-quality issues? Or is the real concern with leavening: that excessive prefermentation exhausts food supply and, thus, yeast growth stops and begins to die and, thus, preferment gradually loses its capacity to leaven (even if it can still make delicious!).
[I ask this because I tend I tend to use preferments more for flavour enhancement, less for leavening (i.e. I'm perfectly happy to use a bit of commercial yeast in the final dough knowing that my preferment has done the work to extract flavour.) Thus, my thinking: If I were to stop using commercial yeast in final dough altogether (what some consider a crutch or inauthentic), I'd better learn something (pay more attention to) ripeness–and stop being comfortable with my preferment doing its thing for 16, 24, oops! 30 hours!]
(Sorry for the circular logic, if it can indeed be called logic. My brain is not a linear enterprise, so I'm fully comfortable asking stupid questions if the result makes me less so.)