What does the ash content of broken wheat really mean?
The "Ash" is not an ingredient in the flour

To be clear, the "Ash" is a measure of what you'd get left - if you burned the flour. It is not an ingredient in the bag of flour.

More specifically if you had 100g of flour - the "Ash" number is literally how much the Ash would weight if you burned all of it. As starch burns readily, what you'll be left with is mainly minerals.

Some people will determine various properties of the flour based on this Ash number. For one, a higher Ash number generally means more of the wheat's non-endosperm parts were included in the flour.

As milling is generally the process of separating the endosperm from the rest of the wheat; a less effective milling process will result in a higher Ash figure. So in a way, you can consider it to be a quality measure. But in other ways, it's just another indicator of "what exactly is in the bag".



Some useful sources:

Joe Pastry

Ash in the flour

NDSU