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A Radioisotopic Study of the Entry of Calcium Ion into the Maize Kernel During Nixtamalization

¹Departamento de Bioquímica, Instituto Nacional de Cardiología, Mexico City, Mexico, C.P. 14080. ²Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada del I.P.N., Unidad Querétaro, José Siurob 10, Col. Alameda, Querétaro, Mexico, C.P. 76040. ³Laboratorio de Física Aplicada y Tecnología Avanzada, Instituto de Física, UNAM, Campus Juriquilla, Apdo. Postal 0-1010, Querétaro, Qro., Mexico. ⁴Departamento de Ingeniería Genética de Plantas, CINVESTAV-Irapuato, A.P. 629, Irapuato, Guanajuato, Mexico, C.P. 36500. ⁵Corresponding author. Phone/fax: 52-4422129466. E-mail: Reynaldo.Pless@cicataqro.ipn.mx.

The entry of calcium ions from the nixtamalization solution into maize kernels over time was followed in model experiments using radiolabeled calcium ions, with autoradiographic evaluation of the kernels after different cooking and steeping times. Calcium ions immediately entered the pericarp and were rapidly fixed at the outer boundary of the endosperm, especially at the external surface of the germ. Entry of calcium into the endosperm occurred gradually after long steeping times, except in the case of broken kernels, for which massive invasion by calcium was observed. After extended steeping times, a moderate amount of calcium-45 was evident in the germ. Specific perforation of the outer layers of the grains provided a defined route of facilitated entry of calcium into the endosperm. No fundamental difference with respect to penetrability by calcium ion was seen in a comparison between flint-type grains and grains containing only floury endosperm.