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Assessing Degree of Cook During Corn Nixtamalization: Impact of Processing Variables¹

¹Journal Series No. 12543, Agricultural Research Division, Institute of Agriculture and Natural Resources, University of Nebraska-Lincoln. ²Postoctoral research associates, University of Nebraska-Lincoln. ³Research technicians, University of Nebraska-Lincoln. ⁴Associate professor, Cereal/Oilseed Science and Technology Laboratory, Dept. of Food Science and Technology, University of Nebraska-Lincoln, Lincoln, NE. ⁵Corresponding author. Phone: 402-472-2814. Fax: 402-472-1693. E-mail: djackson@unlnotes.unl.edu

Nixtamalization involves cooking and steeping corn in a lime solution, washing the corn (nixtamal), and stone grinding nixtamal to form a corn dough or masa. Masa is used to produce nixtamalized products (corn tortillas, tortilla chips, corn chips, taco shells, etc.) by forming and baking or deepfat frying. The degree of corn kernel cook determines the quality and texture of masa. Response surface methodology (RSM) was used as an experimental design to study the impact of process variables (cook temperature, cook time, initial steep temperature, and steep time) on the degree of cook measured using a Rapid Visco Analyser (RVA) and differential scanning calorimetry (DSC). RSM data exhibited significant (P < 0.005), although not predictive, linear models for RVA peak viscosity (r² = 0.63), setback (r² = 0.61), final viscosity (r² = 0.61), and peak time (r² = 0.57), indicating a dependence of these parameters on nixtamalization conditions. Peak viscosity, setback, and final viscosity increased linearly with steep time. DSC enthalpy (r² = 0.83) and peak temperature (r² = 0.89) of freezedried masa also exhibited significant (P < 0.0001) linear regression models with processing variables. DSC enthalpy increased with an increase in steep time, suggesting that starch is annealed during steeping. This study demonstrated that fundamental starch properties were altered on extended steeping during nixtamalization.