Starch based microcellular foam particles with a porous structure, high surface area and high brightness were produced with a simple precipitation process with ethanol. The addition of alkyl ketene dimer to the starch imparted some amount of water resistance to the particles. The activity of the AKD was most importantly a surface coating phenomena. Surface coating of the AKD on the particles, rather than blending the AKD and the starch, was a more effective method to increase water resistance.