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FSB1 – 2004 Food Science and Biotechnology in Developing Countries 6. Pérez L. González-Martínez C. Chafer M. Chiralt A. Cambios de color en Pera (var. Blanquilla) mínimamente procesada. Departamento de Tecnología de Alimentos, Universidad Politécnica de Valencia. Camino de Vera s/n, 46022 Valencia, España 7. Ponting J.D. Joslyn. M.A. 1948. Ascorbic acid oxidation and browning in apple tissue extracts. Arch. Biochem. Biophys. 19: 49.
Water and calcium absorption during corn nixtamalization Herrera-Rivera, R.H., Alvarado-Garcia, M..A., Monroy-Rivera J.A. (jamonroy@itver.edu.<strong>mx</strong>)UNIDA-Instituto Tecnologico de Veracruz, Mexico. Corn is the base staple food of Mexican diet. Nixtamalization is a limetemperature process used in corn transformation to rend it into a functional product. In this work, the water and calcium absorption by the grain were studied. Six nixtamalization temperatures (25, 35, 45, 70, 80 and 90°C) and three lime concentration (1, 2 and 3%) were evaluated using a complete factorial statistical design. The results showed that water absorption was produced during the first 10 hours of soaking which was mainly influenced by temperature but not by the lime concentration as well as the calcium absorption into the corn. Nevertheless, the diffusion coefficient calculated through the Fick mass transfer equation was independent of lime concentration and temperature. KEY WORDS: Corn nixtamalization, water absorption, calcium absorption, Fick, diffusivity. INTRODUCTION Corn nixtamalization is a process used to produce tortillas, toasted ships and nixtamalized corn flour. These products are the base of a variety of Mexican food products. The nixtamalization process is an alkaline cooking process followed by soaking. During this process, many physical-chemical, rheological and structural changes take place, which are very important in the final texture characteristics of the tortilla. Mexican culinary culture has been progressively increased in the last years. Nowdays, the industrial production of corn dough (masa) and tortilla does not use the traditional conditions of nixtamalization, reducing texture and stability characteristics of tortilla (2). During Nixtamalization, corn starch is gelatinized and then just after the end of thermal treatment effect, starts the retrogradation (3). These phenomena have a great influence on the mechanical properties of the tortilla. The final calcium content of the tortilla changes the textural smoothness during storage (4). The cross linkage between starch and calcium is controlled by the lime concentration and cooking and stepping times. For consumers, the tortilla is a very important calcium source. Biological studies have shown that practically all this calcium is available (1). Calcium ion absorption during nixtamalization is developed in a progressive way from the outer surface towards inside layers. In non damaged grains, this diffusion takes several hours (5). Studies on thermal diffusivity of tortilla have shown that there is a maximal value of this property in a short range of the tortilla calcium content (6). The calcium absorption is then an important variable to control during nixtamalization process. In this work, the water and calcium absorption by the corn grain was determined and the Fick mass transfer equation was used to estimate the mass diffusion coefficients.
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