Flour ash is the mineral residue left after incinerating a flour sample, expressed as a percentage, usually on dry matter.
In trade practice
Minerals concentrate in the bran, so ash shows how refined a flour is. German and French flour type numbers are read as ash on dry matter; they are national conventions, not EU law. ISO 2171 is the reference method.
In a specification
Write an ash band on dry matter with ISO 2171 named, rather than a grade name.