Basically what I know about poolishes, bigas
, etc., I summarized recently at Reply #15, at http://forum.pizzamaking.com/index.php?topic=878.0
But what pftaylor is doing to build up and strengthen his biga
is the standard approach recommended and used by most sourdough aficianados. Usually the decision that one has to make when contemplating a poolish is whether it will use natural yeasts or commercial yeast. Once that decision is made, the poolish has to be periodically replenished, by discarding part of the poolish and adding fresh flour and water. This is done repeatedly to strengthen the poolish. Otherwise, the leavening power of the poolish will be weak (insufficient yeast growth and reproduction) and it will be difficult to produce a good dough with good rising qualities. If the replenishment is not done regularly, the poolish will weaken as the yeast uses up all the natural sugars in the flour. It can be rejuvenated thereafter up to a point (if the yeast hasn't been allowed to die through neglect), by using the same replenshment techniques, but more replenishment sequences are required.
Most often, the poolish will contain only flour, water and yeast (natural or commercial), and no salt, which would impair yeast performance, especially if the poolish is just getting started and is based on natural yeasts. But many people are fond of tossing all kinds of things into their starters, as you will note if you do a Google search on the subject.
As for what Patsy's does, Jeff Verasano reported in a recent posting that he believes that Patsy's is using a piece of old dough (chef
) for leavening the dough for the next production. This is a technique commonly used by bakers in France. I suspect that Patsy's uses commercial yeast for the basic dough, as apparently Jeff does, and supplements it with the poolish. I understand that Una Pizza in NYC also uses old dough, except in their case they are apparently using a chef
in the form of a levain
, which is simply a poolish based on natural yeast. It's conceivable that Una Pizza uses only the levain
and no commercial yeast whatsoever, just as is done by many artisan sourdough bread bakers, but this is only speculation on my part. The principal objective in using poolishes, of course, is to get improved crust flavor through all the by-products of fermentation (alcohol, acids, etc.). And it's one of the best ways of getting it.
Tonight I spent some time trying to calculate the baker's percents for jftaylor's recipe as recited above in this thread. Rather than posting the calculations here, I will do so at the Getting Closer to Patsy's Pizza thread once I have finished the calculations.