The effect of solids content and the presence of bonding agents (CMC and/or gelatin) on the physical characteristics of rice starch spherical aggregates were investigated. Rice starch spherules were produced by spray-drying at 120 degrees C according to a 2((k - p)) Fractional Factorial Designs at 2 Levels. Particle size analysis, spherules' morphology, porosity and crystallinity determination were obtained for the aggregates produced. Results showed that the size of spherules is significantly affected by starch concentration while the presence of bonding agents seems not to have a direct influence in particle size. The drying process did not yield a change in crystal type but the presence of gelatin leads to a decrease in crystalline regions. Starch and bonding agents' concentrations did not significantly affect neither the total porosity of the samples nor the average pore diameter. Intra-particle porosity is mainly dependent on starch and gelatin concentrations. This study would be helpful in establishing the more adequate conditions useful in an industrial application on encapsulating bioactive compounds. (C) 2010 Elsevier Ltd. All rights reserved.