The kinetic behavior during tomato seed protein recovery by alkaline extraction followed by protein investigated. A simple method for predicting the effective diffusion coefficients from the experimental kinetics with suitable transformation to rate of extraction versus time was presented. The method is based on treatment of the Regular regime curve for internal diffusion rate limiting finite batch process. A diffusion coefficient of 3.0 x 10(-11) m(2) s(-1) was calculated for the optimum operation conditions. Numerical kinetic curves using the finite difference method were obtained, as a simulation of the experimental data. A good fit with experimental data was obtained. (C) 2003 Elsevier Ltd. All rights reserved.