|Husband and his "Busy Miller's Miche"|
To produce 100%-extraction flour, once the whole wheat berries are milled, none of the bran is filtered (or "bolted") out, and the miller's job is done. For comparison, in The Bread Baker's Apprentice (p.242), Peter Reinhart tells us Poilâne's miche is made with flour of 90-95% extraction. To produce 90%-extraction flour, the miller filters or "bolts" the flour in such a way that 10% of the total weight of the wheat is caught by a filter. These bits of wheat are the larger pieces of bran.
Husband's "Busy Miller's Miche," pictured above, was baked yesterday, is 3 kilograms (6.5 pounds), and was made with a mixture of bread flour (40%) and unbolted, whole wheat bread flour (60%) from Roger's Creek Grist Mill, our local mill.
Update: For more on the extraction percentage of flour, check out Controlling the Extraction Percentage of Flour, at Home.