Physiochemical changes of starch during maize tortilla production

The physiochemical changes of starch in maize tortillas and their intermedi ate products commercially processed by the traditional way have been determ ined. Samples of maize, nixtamal, dough or masa, tortilla and nejayote (ste ep liquor) were analyzed. The samples were assayed for water absorption ind ex (WAI), resistant starch (RS), X-ray diffraction patterns, viscosity and with Differential Scanning Calorimetry (DSC). Enthalpy of fusion (Delta H), initial temperature (T-o) and transition temperature (T-p) of gelatinizati on were obtained from DSC curves. Resistant starch contents increased as th e products advanced in the process. Significant differences (p > 0.05) in t he fusion enthalpy values of maize, nixtamal and masa could not be found. X -ray diffraction patterns of maize, nixtamal and masa did not show signific ant changes; however, when masa was transformed into tortillas there was a large loss in crystallinity. The viscoamylograph peak viscosities increased from maize to masa and decreased drastically in tortillas. The data showed that the tortilla baking stage caused the most pronounced changes in starc h.