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Water and calcium absorption during corn nixtamalization
Herrera-Rivera, R.H., Alvarado-Garcia, M..A., Monroy-Rivera J.A.
(jamonroy@itver.edu.mx)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.