STUDIES ON THE WASHING OF MILLED RICE - SCANNING ELECTRON-MICROSCOPIC OBSERVATION AND CHEMICAL STUDY ON SOLUBILIZED MATERIALS

During four times washings, milled rice lost about 2.3% of material. The first washings contained 61% of the total solubilized material during these treatments. Gradual loss of various of kinds of nutrients was observed during repeated washing of rice. The great losses observed were in crude fat (65%) and in ash (49%). The loss of protein during, however, was only 6. 3%. Total phosphate, as well as the phytin phosphate, decreased during the washing process. AG 1-X 2 ion exchange chromatography was used to separate phytin phosphate. The main component was inositol hexa-phosphate (50%) and minor components were inositol penta, tetra, tri and di-phosphates. Trace amount of inositol mono-phosphate was also present. The endosperm structure of the washed rice grains was examined with light and scanning electron microscopes. Light micrography of the surface structure of washed rice showed cracks 6 minutes after washing. With scanning electron microscope, numerous particles, which were probably aleurone particles, were observed on the surface of milled rice. However, these particles disappeared and cell wall was exposed by repeated washing. Endosperm materials and aleurone materials could not be distinguished by the observation of first washings, but in three or four times washings were observed starch granulum, protein bodies, phytin particles and aleurone particles. © 1979, Japan Society for Bioscience, Biotechnology, and Agrochemistry. All rights reserved.