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.

Nutraceutical, Physicochemical, and Sensory Properties of Blue Corn polvorones, a Traditional Flour-Based Confectionery.

Blue corn is an anthocyanin-rich material that can be used in the preparation of baking products. The aim of this work was to evaluate the physicochemical, nutraceutical, and sensory properties of polvorones (a traditional flour-based confectionery) made with whole blue-corn flour. All samples showed similar bromatological composition, but polvorones from whole blue-corn flour had a higher phenolics (837.1 mg gallic acid/kg) and anthocyanins (373.0 mg cyanidin-3-glucoside/kg) content, which exerted an influence on their higher antioxidant activity compared with wheat flour-based laboratory and commercial samples. The transformation of raw blue-corn flour into polvorones produced the degradation of some acylated anthocyanins into non-acylated forms. The substitution of wheat flour with whole blue-corn flour enhanced overall acceptability, as well as the color and flavor of polvorones. Our findings demonstrated that it is possible to use whole blue corn in the formulation of polvorones with more health beneficial properties and better consumer acceptability than refined wheat products.

Viscoelastic behaviour of masa from corn flours obtained by nixtamalization with different calcium sources.

The viscoelastic characteristics of nixtamalized corn masa were assessed by the dynamic oscillatory test. Masa samples were prepared with flours obtained by nixtamalization with different calcium sources: Ca(OH)2 (traditional), wood ashes (classic), CaCO3 (ecological), CaSO4 (ecological), CaCl2 (ecological), and Ca(C2H5COO)2 (ecological). A sample cooking without calcium source was used as control. Storage (G') and loss (G'') moduli were higher in masa from traditional and classic processes indicating a more elastic and viscous masa. Masa of flours from CaCl2 and Ca(C2H5COO)2 had the lowest values of G' and G''. Viscoelastic properties were explained in terms of the degree of starch gelatinization, the hydrolysis of pericarp and fibre content, the calcium-starch and calcium-zein interactions, as well as the presence of amylose-lipid complexes. Nixtamalization with Ca(OH)2 and wood ashes gave the best viscoelastic characteristics of masa.

Physicochemical properties of nixtamalized black bean (Phaseolus vulgaris L.) flours.

The aim of this work was to study the effect of three nixtamalization processes using wood ashes, Ca(OH)2, and CaCl2 on the physicochemical properties of beans. Raw beans had C-type starch, 10.10% resistant starch (RS), and two DSC endotherms: 1) starch gelatinization, and 2) melting of amylose-lipid complexes plus protein denaturation. Nixtamalization increased the Ca and Fe content, decreased the RS content to 4.19-4.43%, and produced starch retrogradation. DSC and FT-IR analysis of the flours evidenced a "stabilizing" effect of cooking with NaCl and CaCl2 on bean proteins. In contrast, cooking with wood ashes and Ca(OH)2 produced denaturation of bean proteins, decreasing the second transition enthalpy and absorption bands of amide I, II and III. Results showed that traditional and classic nixtamalization of beans are alternatives to obtaining mineral fortified flours that could be used as ingredients in the elaboration of foods with a good nutritional profile.

Nixtamalization Process Affects Resistant Starch Formation and Glycemic Index of Tamales.

Tamales were prepared with 3 nixtamalization processes (traditional, ecological, and classic) and evaluated for chemical composition, starch properties, and glycemic index. Resistant starch (RS) in tamales increased 1.6 to 3.7 times compared to raw maize. This increment was due to the starch retrogradation (RS3) and amylose-lipid complexes (RS5) formation. Tamales elaborated with classic and ecological nixtamalization processes exhibited the highest total, soluble and insoluble dietary fiber content, and the highest RS content and lower in vivo glycemic index compared to tamales elaborated with traditional nixtamalization process. Thermal properties of tamales showed 3 endotherms: amylopectin retrogradation (42.7 to 66.6 °C), melting of amylose lipid complex type I (78.8 to 105.4), and melting of amylose-lipid complex type II (110.7 to 129.7). Raw maize exhibited X-ray diffraction pattern type A, after nixtamalization and cooking of tamales it changed to V-type polymorph structure, due to amylose-lipid complexes formation. Tamales from ecological nixtamalization processes could represent potential health benefits associated with the reduction on blood glucose response after consumption.