Assistance required converting poolish focaccia recipe to sourdough

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I'm using the poolish focaccia recipe from Peter Reinhard's book Bread Bakers Apprentice. I cut the amount in half so it's now like this

10 oz Poolish
6 oz Flour
1 tsp Salt
3/4 tsp instant yeast
1.5 oz Olive oil
3 oz Water

For the Poolish I used my sourdough starter, and modified his Poolish recipe so it became
- 30 g sourdough starter (50% hydration)
- 125 g flour
- 135 g water

So anyway after constructing the poolish and letting it rise for 12 hours at room temperature, I could continue as normal with the recipe and use the instant yeast when mixing the poolish in with the final ingredients. (I did this in the past and it worked fine)

However I was wondering what modification I need to make if I want to skip the instant yeast altogether and go completely sourdough. Do I just eliminate the instant yeast and proceed as normal, but allow for longer proofing times?

However I was wondering what modification I need to make if I want to skip the instant yeast altogether and go completely sourdough. Do I just eliminate the instant yeast and proceed as normal, but allow for longer proofing times?

Exactly! 

My approach is to take about 3% (of the total flour) active culture and use it to "seed" a levain. The levain is typically 15% of the total flour. Mature the levain over 12-14 hours @ 21C. Remove the amount of "seed" once the levain is ready. Extract the flour and water quantities you used in the levain from the final dough mix and add all the levain. Very exact. This a starting point for you to experiment with how much you need. The use of a levain will shorten the BF time.

Gavin

I think you have two options:

  1. Follow the existing formula but replace the yeast in the polish with a bit of starter (say, 10% of the weight of flour or water in the polish), and let it ferment overnight.  You're basically doing what you do when you feed your starter.  The next day, use the polish in the main dough as usual but leave out the commercial yeast.  The fermentation will take longer than it does with commercial yeast.
  2. Build up your starter the day before to the size of the polish, plus a little to keep the starter going.  Start the formula at the final dough using starter equal to the weight of the polish, and leave out the commercial yeast.

Yes, these two are essentially the same.

There are two things I dislike about "The Bread Baker's Apprentice":

  1. Measurements in English units
  2. His confusing instructions for sourdough breads.  I haven't spent the time figuring out what a barm is.

 

What are English units? Grams? Most of the world uses grams now! 

Barm? Well barm originally was the yeast enrcihed froth taken from a fermenting beer and mixed with some flour and allowed to become bubbly. This was then used as a leavener in the dough. So essentially it is a kind of poolish and probably used interchangeably. 

I should have written traditional, imperial, or non-metric units.  Ounces, pounds, teaspoons, and cups are called all of those in the USA, as well as English units.  They are a PITA for baking if you want to, say, double or halve a formula.  Metric units, grams, and milliliters (or kg and liters for a big batch) are vastly easier to use, especially for adjusting the size of the batch.

In the sourdough chapter of BBA, Reinhardt calls the flour and water mixture that captures local yeasts when you first build a culture, the "seed culture".   After 4 days, he says mix the seed culture with a bunch of flour and water to make a barm.  

For baking bread, he says mix the barm and flour to make a starter.  Ferment for 4 hours, then refrigerate overnight. The next day, warm up the starter out of the fridge, and mix it with flour etc. to make the dough.

I suppose it's not really much different from other multi-stage formulas, especially for rye breads.  But somehow it seems more complicated that the usual basic sourdough bread schedule, eg.:

  • Day 1 AM - Feed the starter (my rye starter feeding from "The Rye Baker" is 7g starter + 70g warm water + 70g whole rye flour)
  • Day 1 PM - Mix the levain/sponge: starter and some more flour and water and ferment overnight
  • Day 2 AM - Mix final dough, ferment
  • Day 2 PM - Divide, shape, proof, bake

I'll give him his barm, sometimes I make rye breads with a sponge, scald, and a scald-sponge before getting to the final dough. But there is no excuse for using traditional units in a baking book.