The mathematical modeling of simultaneous size reduction (shrinkage) and shape change (deformation) during food drying was investigated. A whole new approach was developed for (i) solving the unsteady state mass transfer equation in a deformable mesh and (ii) modeling the simultaneous shrinkage-deformation (SD) of product in drying simulation. The SD model for continuous mesh updating is based on the estimation of the minimum discrepancy configuration. Developed theory was applied to estimate water diffusivities during the analysis of potato drying data (9.525 mm x 9.525 mm x 80 mm, 50-80 degrees C, 2 m/s) by considering the product shrinkage with and without deformation. The drying model including the simultaneous SD rendered the best description of experimental drying curves (R-2 > 0.98). Under current experimental conditions, water diffusivities corrected for simultaneous SD were in the range of 1.93 x 10(-10)-3.44 x 10(-10) m(2)/s. On the other hand, water diffusivities calculated by neglecting product deformation were overestimated in about 57-66% in comparison with those considering the phenomena. The dependency of water diffusivity on drying temperature was unaffected by the inclusion of product deformation in drying modeling. (C) 2015 Elsevier Ltd. All rights reserved.