Is a visual peak, really The Peak?
Disclaimer: I am not asking the question I am about to ask, because I think common wisdom is wrong, and I have a better answer. I don't have an answer, I'm curious, and I've never seen an answer to related questions that wasn't in some way cast in The Common Wisdom.
Common Wisdom: A preferment (poolish, biga, etc., or sourdough starter) is at its peak--"peak" implying maximum yeast reproduction rate, or maximum yeast population size (I've never been entirely certain which)--is indicated by the preferment having reached its maximum expansion, and/or just beginning to collapse in its container.
My starter, at room temperature (~76*F) visually peaks in 7 hours. Since I started baking sourdough, seriously, I've followed Common Wisdom mixing my final doughs as near to the moment my final levain build reaches a visual peak as is practical. The only exception has been when I intentionally let the final build ferment additional time, up to sixteen hours total time, trying to create the elusive sourness. Even if one or more fellow TFL contributers gives me clear, unabiguous and non-conflicting answers that defy Common Wisdom, I'll continue doing what I do now, because I'm content and happy with the consistent results I've finally obtained. This really is only a curiosity only post.
The Question: Does a visual peak, in fact, herald the yeast's maximum point of development measured directly by its rate of reproduction, or its maximum population size, or some other yeast-related paramenter?
I ask this question for two reasons. First my head is awhirl with other, physical and chemical phenomena: mass, temperature, surface tension, partial pressure, gluten tensile strength, gas aggregation (bubble size), proteolytic enzyme activity, and gravity which I imagine effect the point of collapse. (There is likely others I haven't listed.). Secondly, I've had occasion to stir-down active starter at its visual peak, and left it to rest (intentionally, and unintentionally) for a few more hours finding it again peaked at an expansion essentially identical to the first expansion. Furthermore, Except for approximately+15 minutes of final proof time, I've not perceived appreciable variation in final proof surface tension, loaf expansion, or oven spring when I use levain that fermented up to eight hours beyond its visual peak in loaves that are within practical limits otherwise identical.
It's a great rule-of-thumb. I suspect it's been used for millennia. I intend to continue to use it. But what is it really measuring of value or a quantity associated directly with the yeast's performance.?
Perhaps a better question is, "Who really cares? It works!