Sourdough is a naturally leavened dough that does not require the use of commercial yeast.
Instead, the leavening agent comes from a sourdough starter, a colony of yeast cells obtained from the environment and including yeast cells that naturally reside on the flour itself.
These cells constantly feed on the regular addition of flour and water.
As long as the colony is fed, the starter will provide a steady supply of the carbon dioxide that the gives bread its lift.
The book that inspired the Bread Bakery Blog (Della Fattoria Bread) includes instructions for the creation of a starter over the course of 7-10 days of regular feedings of flour and water.
I store my now-established starter in the refrigerator with weekly maintenance feedings. Two days prior to baking bread, I feed the starter in the morning and leave it out, at room temparature.
The following morning I feed it again, and then again in the evening, so that the starter will be at or near its peak active the following morning. I then make dough for bread and while it's bulk proofing, I feed the starter once again and returned it to the refrigerator until the next bake.
The feeding schedule for maintenance of an established starter calls for 153 grams of water, 30 grams of whole wheat flour, and 270 grams of all purpose flour.
I followed that schedule until I started milling my own flour.
But whole wheat and all purpose don't apply to the flour I get out of my mill. My flour contains all of the germ and, no matter how fine I sift, some of the bran that differentiate store-bought all purpose and whole wheat flours.
Additionally, home milled flour—possibly due to the bran and germ—soak up water more than store bought flour.As of this writing, I have been using 300 grams of home-milled flour and 170 grams of water.
I have yet to settle on what kind of flour to use.
Commercial all purpose flour is a compromise between high-protein bread flour and low-protein pastry flour, hence its name, all purpose.
In my new world of flour milling, I have high-protein hard red and durum, somewhat lower-protein hard white, and low-protein soft white wheats.
Based on my limited experience, I'm leaning toward the hard white wheat as my baseline flour. Time and experimentation will tell more, but right now, as of this writing in September 2019, I don't have a definitive answer.
I have made one loaf from each. The loaf made from hard red wheat was heavier, denser, fewer and smaller bubbles in the crumb. One loaf each is not enough to give a definitive answer, but certainly counts as an indicator.
The quest continues.
Extraction rate is the ratio of end product (the milled flour) to source (the quantity of wheat berries) by weight, expressed as a percentage calculated by dividing the weight of the flour by the weight of the wheat berries.
When 1000 grams of flour is milled from 1000 grams of wheat berries, the extraction rate is 100 percent.
If 500g of flour remains after filtering to remove bran, the extraction rate is 50% (500g divided by 1000g).
More simply stated, the percentage of flour obtained from a quantity of wheat berries, measured by weight, is the extraction rate.
Without filtering, 1000 grams of wheat berries should produce 1000 grams of flour. That includes all of the germ and all of the bran, in addition to the flour (the endosperm).
The germ can't be removed from flour milled by a home stone-wheel grinding mill. But the bran can, by sifting the milled flour through a flour sifter.Measuring how much flour gets through the sieve, and how much bran doesn't, produces the extraction rate.
I have two sifters, one a 40-mesh, the other a 50. The numbers refer to how many wires there are per inch in the grid that is the sieve.
With the 40-mesh sifter, I was able to get an extraction rate of 73%&mdasy;327 grams of flour out of 450 grams of wheat berries.
With the 50-mesh sifter, the yield dropped to 168 grams of flour from the same amount of wheat, for a rate of 37%.
My impression from memory is that the bread that resulted from the higher extraction rate was pretty good, not great, but good enough, and I don't recall what became of the flour produced from the 50-mesh screen. These loaves were the first I tried with my new mill, and before the oven failure.
I wasn't yet keeping close track of the process. I had not yet started the bread bakery app/blog. I was just getting acclimated to the world of home milled flour, when the oven failure put everything on hold.
Now that the new oven is in, and the app is functional, I'm going to be recording atttempts and successes in greater detail.