Characterization of rice flour milled with water and effects of soaking conditions

Abstract

High-moisture rice flour was prepared by soaking polished rice in water, which was then ground in an electric ceramic mill and dehydrated by centrifugation. The yield of rice flour milled with water became largely constant with soaking times of 30 min or more at room temperature, and near-constant moisture content was reached with soaking for 50 min or more. The size of most rice flour milled with water particles was around 6 μm, and was not greatly influenced by soaking time or temperature. Starch damage rate was suppressed to an extremely low value of less than 2% with soaking for 50 min or more at room temperature. Investigation of the effect of soaking temperature revealed that there was a positive correlation between soaking temperature and starch damage rate. It is therefore not advisable to raise the soaking temperature above room temperature when milling rice with water.