Effects of Tempering Time, Ca(OH)2 Concentration, and Particle Size on the Rheological Properties of Extruded Corn Flour

Extrusion was used for obtaining corn masa. Particle size, Ca(OH) 2 concentration, and tempering time had significant effects on the viscosity of extruded flours. Ground corn tempered for different periods of time (0.016–10 h) increased viscosity without application of heat. This behavior can be explained by the release of starches from the protein matrix. Viscoelastic properties of masas showed storage modulus ( G ′) > loss modulus ( G ″) for all samples. G ′ and G ″ increased as a function of tempering time, indicating higher water absorption capacity (WAC). The same behavior was found for Ca(OH) 2 concentration, suggesting formation of cross‐links between starch and polymers. Viscosity of masas modeled by the power law showed a value of n close to 0.1, suggesting that the dispersed solid phase was greater than the liquid phase. Index n and consistency coefficient K were associated with water absorption and viscosity, respectively. Regarding Ca(OH) 2 , the higher the Ca(OH) 2 concentration, the lower the index n ; thus, Ca(OH) 2 influenced the pseudoplastic behavior of extruded masas. Index n was directly proportional to WAC. Consistency coefficient K generally increased with the tempering time and small particle size. In addition, viscosity was higher after 10 h of tempering time. Tempering time improved rheological quality of masa obtained by extrusion.