Abstract
The addition of the supernatant derived from enzyme (protease M) - treated rice washing drainage to purified rice starch showed highest sediment ability of starch particles. Besides, phosphate ion discharges from solid particles to the supernatant that were promoted by the addition of protease M, the decrease of the supernatant phosphate concentration after additions of purified rice starch was also observed. Moreover, to determine the dissociation of phosphate ions in relation to flocculation and sedimentation of purified rice starch, these processes were observed with the same pH range under the existing dissociate form of phosphate. In addition, as the results of FT-IR analysis of the solid surface of purified rice starch show, using the same pH the transmittance decrease of the P-O group and the flocculation and sedimentation ability of purified rice starch particles were observed. These results suggest that the occurrence of flocculation and sedimentation of purified rice starch particles as a result of pH dependent dissociate form of phosphate joins with the surface of the starch particles and form negative electron charges derived from the dissociate form of phosphate on the surface of starch particles, respectively. Finally, macromolecules of starch particles were formed by constructing bridges by electrostatic interaction.
