Changes on the structure, consistency, physicochemical and viscoelastic properties of corn (Zea mays sp.) under different nixtamalization conditions

Aqueous corn (Zea mays sp.) dispersions with 1% (w/w) of calcium hydroxide/weight of corn were cooked at 90 °C (nixtamalization) for different times (10, 30, 50, 70 and 90 min), making five treatments. A control lot (nine treatments), was cooked for 10, 30, 50, 60, 70, 90, 120, 150 and 180 min. Then, processed corn samples were washed and milled to obtain masa (dough). Scanning electron microscopy, calorimetry, viscoamilography and rheological analysis were used to characterize the corn samples. The corn micrographs showed that the nixtamalization modified the shape of the starch granules and the protein bodies. Starch granules from nixtamalized samples, were round shaped, while control samples, showed polygonal shape. Proteins from nixtamalized samples usually exhibited two transition endotherms, while in control samples, only one transition was seen, suggesting some relationship with gelatinized starch. The nixtamalization shortened the corn cooking time to develop a proper texture in masa to obtain good quality tortillas, as seen in their consistencies. All corn masa samples showed weak gel-like viscoelastic behavior with the elastic modulus (G′) higher than the loss modulus (G″), over all strain and frequency domains.