Breaking with Tradition, Part 1. Roller Milling of Wheat

The grinding of wheat into flour is mankind’s oldest continuously practised industrial activity and “the parent of all modern industry”. In pursuing the fundamental need for efficient milling of wheat, millers and millwrights of old developed a practical mastery of several of the fundamental engineering disciplines: fluid dynamics and aerodynamics for power generation from water wheels and windmills, mechanical engineering for the transmission of power via gearing and control mechanisms, and particle handling, breakage and separation operations. Then, in the late 1800s, a revolution occurred within flour milling, with the sudden and rapid displacement of millstones by roller mills. This paper will present the historical reasons for this revolution in flour milling, reasons that continue to underpin the global grain trade and the practice of flour milling today. It will then present recent developments in the breakage equation for roller milling, which allows the processing of an inherently variable feedstock to be understood and predicted quantitatively. This engineering understanding of kernel breakage is relevant for wheat processing for food use and, increasingly, for non-food applications as well.