Evaluation of the rheological properties of fresh corn masa using squeezing flow viscometry: Biaxial extensional viscosity

Alkaline corn was cooked for 20, 55 or 80 min, and the nixtamal was ground into masas with medium or coarse particle size distributions. Water was added to each corn masas in order to obtain the same adhesiveness. Rheological properties of these masas were evaluated with the squeezing flow viscometry technique with lubrication at crosshead speeds of 0.05, 0.2 and 0.5 cm/min, respectively. From the data collected, stress-strain and biaxial elongational viscosity-radial extension rate curves were obtained. All the fresh corn masas gave the same stress and elongational viscosity at any given specific strain and radial extension rate, respectively, regardless of the cooking time and degree of grinding. The elongational viscosity could be useful to predict fresh corn masa behavior during molding and cutting steps in the tortilla-making process.