ABSTRACT:In this study, the micro-structure of rice starch was characterized by measuring the particle-size distribution and the water vapour sorption isotherm at ambient temperature. Because of the slow adsorption and desorption processes, the application of the Jäntti extrapolation method was examined. Evaluation of the isotherm was carried out by a modified Frenkel-Halsey-Hill method. A new method describing the hysteresis loop by bond number is presented.