Combined speed and duration of milling affect the physicochemical properties of rice flour

The properties of flour from polished rice that had been subjected to various milling conditions were investigated. Waxy, low- and high-amylose rice were milled at different speeds (1050, 950, and 750 r/min) for different durations (20, 40 and 60 s). The swelling power was increased with milling duration and speed compared to brown rice flour. The solubility of milled waxy rice flour was substantially lower than for brown rice flour, but for milled low- and high-amylose rice flour, it was unchanged or slightly reduced. The peak viscosity of low- and high-amylose rice flour was more affected by milling duration, whereas the final viscosity was more affected by milling speed. Total milling revolutions led to greater effect on pasting properties of WRF than LARF and HARF. Milling duration was a greater determinant of thermal properties than was milling speed. Milling conditions had different effects on the digestibility of different rice flours. Milling speed had less effect on digestibility than did milling duration for waxy rice flour, but speed had a greater effect on the digestibility of low- and high-amylose rice flour. This study showed that both milling duration and speed impacted the physicochemical and digestibility properties of different rice flours, but to different extents.