Evaluation of powder and hydration properties of rice flour milled by different techniques

Rice flour is produced using a variety of milling techniques and has been utilized in many different types of food. Characteristics of starch have been shown to differ depending on the milling technique. However, there are few reports showing the relationship between particle diameter and various starch properties. In this study, we aimed to clarify the powder and hydration properties of rice flour. Regarding microstructures of rice flour particles, starch structure was observed in the flour produced by wet milling but not by dry milling. In the flour produced by dry milling, there were no clear relationships between particle diameter and starch properties. However, starch in rice flour produced by wet milling was damaged and crystallinity was decreased. From the hydration characteristics curve, hydration behavior was found to be especially slow in the dry milling sample with small particle diameter. In addition, the correlation between starch damage level and the hydration rate coefficient was shown. These findings indicate that hydration behavior is closely related to starch properties and that hydration rate coefficient is an important factor in utilizing rice flour in food products.