Ash is what you thought it was. Lots of flour are tested for consistency so
that the milling companies can give consumers something consistent. They
undergo farinographs and other tests to determine protein content,
stability, and peak kneading time. A small portion of flour is burned, and
whatever remains in referred to as ash. It is a measurement of the mineral
content of the flour. The ash that remains is minerals, which in turn are
good food for yeast, especially wild yeasts for sourdough. They also
detract from that brilliant white color that the public demands from their
flour.
- Randy Clemens -