Effect of Calcium Salts Concentration on the Viscoelastic Properties of Sintered Tablets from Flours and Tortillas Evaluated by Stress-Relaxation Tests.

This research aimed to evaluate the effect of different calcium compounds and their concentration on the viscoelastic parameters of flours and tortillas obtained with traditional and ecological nixtamalization. Specimens (tablets) of nixtamalized flours and tortillas (14% moisture) prepared with three different calcium sources and four concentrations were sintered using a die and a hydraulic press and were evaluated by stress-relaxation tests with a texturometer. Data collected from the stress-relaxation curve were fitted into a three-element generalized Maxwell model (r2 = 0.9999), allowing the detection of significant differences in the estimated viscoelastic parameters. When flours are processed into tortillas, the most notable change was the increase of +88.44% and +73.44%, respectively, in the summation of the elastic modulus, and the compressional viscosity in samples produced with CaCO3. On the contrary, tablets from samples with Ca(OH)2 presented a sharp diminishing (loss) in both of the evaluated viscoelastic parameters, accounting a decrease of -39.82% and -46.28% for the elastic modulus and compressional viscosity summations, respectively. Highly significant correlations were found among viscoelastic parameters when a slight proportional increase was observed in the specific elastic moduli, meaning that the energy was stored by each elastic element in the tablets, while the compressional viscosity coefficients varied as a function of time. Finally, it was found that the residual spring due to the pure elastic component (E0 ) stored energy during the entire test. PRACTICAL APPLICATION: There is no published information about a simple methodology for the evaluation of the viscoelastic properties of dry nixtamalized flours (powder) with a texturometer. The method proposed was sensitive and accurate, since it was capable of detecting differences among samples processed under distinct processing factors conditions. The study of viscoelastic properties of grain foods contributes to the construction of molecular theories occurring in their chemical compounds, which is strongly related to food texture. Those theories are handy to improve nutritional and textural properties of grain foods and are essential to powder handling, processing, and transportation, which allows the processing factors optimization.