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Tortilla samples were elaborated by four small commercial factories in Mexico, employing masas prepared with the traditional nixtamalization process. Samples were stored at 4 ºC for up to 72 hours and their chemical composition and in vitro starch digestibility features were evaluated. Chemical composition did not change with the storage time, but soluble carbohydrates decreased slightly during storage. A significant decrease in available starch content upon storage was observed, concomitant with increased resistant starch (RS) levels. These changes are possibly due to retrogradation. Retrograded resistant starch (RRS) values increased with storage time; in some samples, RRS represented more than 75% of total RS whereas in others it only accounted for 25%. The digestion rate (DR) in the freshly prepared tortillas was similar for the various samples, but after 72 h storage some differences among tortillas were found. Also, when a single tortilla sample was compared throughout the different storage times, lower DRs were determined in samples subjected to prolonged storage, which is related to the concomitant increase in RRS. The differences found among the various tortilla samples may be due to minor variations in the commercial processing conditions and to the use of different corn varieties.Se elaboraron tortillas utilizando masa a partir de cuatro tortillerías, la cual fue obtenida mediante el proceso tradicional de nixtamalización. Las muestras fueron almacenadas a 4 ºC hasta por 72 h y se determinó su composición química y digestibilidad del almidón in vitro. La composición química no cambio con el tiempo de almacenamiento, pero los carbohidratos solubles disminuyeron ligeramente durante el almacenamiento. Se observó que el contenido de almidón disponible disminuyó y el almidón resistente (AR) se incrementó con el tiempo de almacenamiento. Estos resultados se deben posiblemente a la retrogradación del almidón. Los contenidos de almidón resistente retrogradado (ARR) se incrementaron con el tiempo de almacenamiento; en algunas muestras el ARR representó más del 75 % del AR total y en otras muestras fue sólo el 25 %. La velocidad de digestión (VD) en las tortillas recién elaboradas fue similar, pero se encontraron diferencias significativas entre las tortillas almacenadas por 72 h. Al comparar las VDs de las tortillas a los diferentes tiempos, se encontró que disminuyeron significativamente con el tiempo de almacenamiento, lo cual esta relacionado con el incremento en el contenido de ARR. Las diferencias determinadas en las tortillas pudo deberse a variaciones en las condiciones del proceso de nixtamalización que usa cada tortillería así como la variedad de maíz utilizada.

Tortilla samples were elaborated by four small commercial factories in Mexico, employing masas prepared with the traditional nixtamalization process. Samples were stored at 4 ºC for up to 72 hours and their chemical composition and in vitro starch digestibility features were evaluated. Chemical composition did not change with the storage time, but soluble carbohydrates decreased slightly during storage. A significant decrease in available starch content upon storage was observed, concomitant with increased resistant starch (RS) levels. These changes are possibly due to retrogradation. Retrograded resistant starch (RRS) values increased with storage time; in some samples, RRS represented more than 75% of total RS whereas in others it only accounted for 25%. The digestion rate (DR) in the freshly prepared tortillas was similar for the various samples, but after 72 h storage some differences among tortillas were found. Also, when a single tortilla sample was compared throughout the different storage times, lower DRs were determined in samples subjected to prolonged storage, which is related to the concomitant increase in RRS. The differences found among the various tortilla samples may be due to minor variations in the commercial processing conditions and to the use of different corn varieties.