Hammer and Roller Milling of Yellow Split Pea
Abstract
Blending nutrient-rich pulses into cereal-based convenience foods could benefit consumers and the cereal and pulse industries but first requires appropriate milling of raw pulses, for which there is no standardized method. Roller milling is the standard method for wheat flour production, but hammer milling is simpler and more cost-effective. Literature documenting pulse flour quality from either system is limited. The goals of this research were to evaluate (1) the effects of hammer mill setup and seed moisture on quality and flowability and (2) the differences between hammer- and roller-milled quality for yellow split pea. For (1), yellow split pea samples at 9 and 11 % moisture were hammer-milled at two rotor speeds (34 and 102 m/s) and with nine mill screen apertures (0.84 to 9.53 mm) and physicochemical properties and flow properties on 6 surfaces were evaluated. For (2), yellow split pea at 11 % moisture was hammer-milled at 102 m/s through a 0.84 mm screen or roller-milled using a two-pass setup, then sieved through a 150 µm screen and evaluated for physicochemical and functional quality. Hammer mill settings had no practical impact on proximate composition, small impact on damaged starch content, and considerable impact on particle size distribution, pasting properties, and flowability. Particle size parameters impacted color, bulk density, pasting properties, and flowability. Flowability was highest on aluminum and lowest on high-density polyethylene. Hammer milling at 102 m/s rotor speed with 0.84 mm screen aperture produced particle sizes closest to that of flour (D10, D50, and D90 of 12, 98, and 348 µm, respectively). Small differences were observed in the D10, starch damage, moisture, peak and final viscosities, and oil binding capacities of hammer- and roller-milled split pea flours. Data from this research supported the viability of hammer milling to produce split pea flour and provided systematic data to support milling, product development, conveying, and storage operations involving split pea and other pulses.