This article describes an optimizer developed for the determination of the effective diffusivity of moisture described by analytical solutions with boundary condition of the first kind. The domain of the diffusivity is scanned from a value near zero up to such a value that the minimum chi-square can be determined. This mechanism of scanning dispenses the information of a search interval for the determination of the optimal value for the diffusivity. The first 200 terms of the analytical solution of the diffusion equation for spherical geometry were coupled to the optimizer, and the effective diffusivity of drying of cowpea was determined. (c) 2009 Elsevier Ltd. All rights reserved.