Confused about Poolish
I found the folllowing guidelines for Poolish on the Internet:
This method is composed of two phases. The first phase is the preparation of a semi-liquid dough comprised of yeast and an equal quantity of flour and water, which is prepared some hours prior to the preparation of the final dough. The second phase is the preparation of the final dough prior to baking.
The purpose of the preliminary phase is to allow for a rapid multiplication of yeasts, which leads to an increase in the strength and rising ability of the subsequent dough.
The percentage of yeast is based upon the amount of flour in the poolish, and varies according to the time in which the poolish is left to ferment. The following percentages are recommendations:
2.5% of yeast for 2 hours of fermentation at ambient temperature
1.5% of yeast for 3 hours
0.5% of yeast for 8 hours
0.1% of yeast for 12-16 hours
It makes logical sense to me that the greater the time period, the less yeast would be needed.
What confuses me is that I am seeing a number for recipes with poolish which have a much greater percentage of yeast than these guidelines indicates, in relation to the time period. Examples are Floyd's Italian Bread and Hector's Cuban Bread (Hector doesn't call it poolish, he calls it starter, but it looks like a poolish to me. Both of these call for equal amounts of flour and water by volume, not by weight. I don't know what impact that has.
What is the effect of using relatively large amount of yeast and then letting it sit at room temperature for as much as 16 or 24 hours? Isn't there a point where that much fermentation has a negative effect?