We report the calcium ion diffusion through the different parts of the maize kernel during microwave nixtamalization, as a function of steeping time, and for two cooked processes, one for 100 min at 72 degrees C and the other for 45 min at 92 degrees C. In each case, we carried out several nixtamalization processes, with different steeped time, from 0 to 24 h. By means of atomic absorption spectroscopy we measured calcium content in pericarp, germ and endosperm obtained from maize kernel after each nixtamalization process. We obtained a notable difference of calcium content in those different parts of the maize kernel, being a bigger quantity in the pericarp and smaller in the endosperm. Calcium ion diffusion in the pericarp, and endosperm show a no linear dependence with the steeping time and a notable increasing with the cooked temperature. This behavior, for higher temperatures, is due to faster pericarp degradation. In the other hand, calcium ion diffusion in the germ shows an irregular linear dependence with the steeping time, as well as, an increase of calcium ion diffusion with the cooked temperature for steeping time smaller than 12 h and a decrease of calcium diffusion with the cooked temperature for steeping time bigger than 12 h. This last, is due to the lost of part of the germ surface, which is rich in calcium content, during the rinsed process, which it has a bigger damage for highest cooked temperature. (c) 2005 Elsevier Ltd. All rights reserved.