Preconditioning effects of brown rice for extrusion: drying of grains, grinder type and wetting of particles
Rice, whole grain, food extrusion, physical property, milling
Particulate solids from brown rice grains were obtained considering the grains moisture before grinding (9 or 6%), the grinder type (disc mill or roller mill) and wetting of the granular material (11 or 14%), aiming to correlate the feed material porosity with the torque generated during its extrusion process. Reduction in grains moisture affected the granular swelling/leached amylose of starch fraction, as evidenced by decrements in peak viscosity and peak gelation. The drier the grains are fed to the mill, coarse fractions decreased and fine fractions increased in the granular materials. Flours from roll mill had a narrower particle-size distribution and more interparticle porosity. In contrast, flours from disc mill had a widespread particle-size distribution and less interparticle porosity. Porous granular materials delivered more air volume inside the extruder barrel, increasing screw filling and torque.