Why is flour collected at several stages during the gradual reduction milling process?

In the gradual reduction milling process, flour is collected at several stages because the milling system is designed to progressively release the inner endosperm from the grain.1

Rather than attempting to reduce all material to flour at once, the process uses a series of break and reduction rolls to gradually free the endosperm in the form of semolina. After each pass through these rolls, the product is sieved to separate the flour that has been successfully released.1

Collecting flour throughout these multiple operations serves several key purposes:
* Purity Control: The process generates numerous flour streams of varying states of purity and freedom from branny specks. By separating these streams, millers can select and combine them to create different grades of flour, such as high-quality patent flour.1
* Efficiency: Each reduction roll further breaks down the semolina while flattening bran particles, which facilitates the subsequent sieving and purification of the remaining endosperm.1
* Flexibility: This multi-stage approach allows for the production of specialized flour varieties tailored for specific uses, such as bread-making or confectionery.1