Changes in the thermal and structural properties of maize starch during nixtamalization and tortilla-making processes as affected by grain hardness

The objective of this work was to evaluate the changes in the thermal and structural properties of maize starch during nixtamalization and the tortilla-making process and their relationship with grain hardness. Three maize types with varying hardness (hard, intermediate, soft) were processed by three nixtamalization processes (classic, traditional and ecological). Starch from the three maize types showed an A-type pattern and two endotherms corresponding to gelatinization and melting of the Type I amylose-lipid complexes. After cooking and steeping, in intermediate and soft grains the partial gelatinization and the annealing affected the starch properties and promoted the formation of amylose-lipid complexes. These effects were not observe in hard grains. The increase in melting enthalpy and the intensity of the peak 2θ∼20° from nixtamal to tortillas demonstrated the formation of amylose-lipid complexes. A third endotherm above 114 °C in some treatments of nixtamal and tortilla starch demonstrated the transformation of some amylose-lipid complexes in a most ordered structures (Type II complexes). The V-type polymorph structure found in native starch, nixtamal, and tortilla corresponds to a coexistence of Type I and Type II complexes. Formation of amylose-lipid complexes in tortillas had a partial effect on decreasing starch retrogradation (r = −0.47, P < 0.05).