Extraction rate is the percentage of flour obtained from a given quantity of cleaned grain in milling, from close to 100 per cent for wholemeal to roughly 70 to 80 per cent for white flour.
In trade practice
Higher extraction brings more bran and germ into the flour, so ash, colour, fibre and enzyme activity rise. Extraction is a mill figure; the buyer usually controls the result through the ash band rather than the extraction rate itself.