Characterization of starches isolated from Mexican pulse crops: Structural, physicochemical, and rheological properties.

This work aimed to characterize and compare the physicochemical properties of four pulse starches: bean, chickpea, lentil, and pea. Chemical proximate analysis, elemental composition, morphological grain characterization, crystalline structure, thermal analysis, FTIR analysis, and pasting properties were conducted. The proximate analysis shows that these starches have low fat, mineral, and protein content but high amylose values ranging from 29 to 36 % determined by colorimetry. Despite the high amylose content, the starches did not exhibit the typical behavior of an amylose-rich starch, with high peak viscosity and low breakdown and setback. It was found that this behavior was likely due to the large granule size of the ellipsoidal, spherical, and kidney-shaped granules and the high content of some minerals such as Na, Mg, K, Fe, Mn, P, and Si. The study also found that all pulse starches simultaneously contain monoclinic and hexagonal crystals, making them C-type starches. The findings were verified through the Rietveld analyses of X-ray diffraction patterns and differential scanning calorimetry, in which bimodal endothermic peaks evidenced both types of crystals being gelatinized.

Amylose-lipid complex formation from extruded maize starch mixed with fatty acids.

Functional modifications of starch, such as paste properties, retrogradation, water absorption indexes, solubility, and swelling capacity, are induced by the amylose-lipid complex. This research comprehends the study of functional properties of extruded maize starch mixed with fatty acids (stearic acid, oleic acid, and maize oil) and the formation of amylose-lipid complexes. Maize starch with lipids (5 or 10 %), moisture (35 %) was extruded (single screw). Starch granule was modified by extrusion, to a lesser extent at 10 % of lipids, especially stearic acid, which covers starch granule surface. Viscosity decreased meaningfully with stearic acid addition. DSC showed both starch gelatinization enthalpy and amylose-lipid complex enthalpy for stearic or oleic acid, but it was just the first enthalpy for maize oil. X-ray diffraction showed orthorhombic crystals with or without the presence of lipids. Our results indicated that stearic acid yielded the highest amount of amylose-lipid complexes.

Physicochemical characterization of quinoa (Chenopodium quinoa) flour and isolated starch.

This work studies the physicochemical properties of quinoa flour and isolated starch. Starch in the seed forms clusters rich in amylopectin that are immersed in a matrix with spherical and polygonal shapes in the submicron scale. The isolated quinoa starch is rich in Sulphur and Magnesium. The quinoa flour has a higher content of protein, carbohydrates and lipids than isolated starch. Water absorption and water solubilized indexes of starch exhibited high values that could had originated by the extraction method. The broad peaks found for the X-ray patterns of isolated quinoa starch indicate that amylose and amylopectin are composed by nanocrystals, according to the PDF-4+2019 software. The viscosity of isolated starch had a higher value than flour; therefore, the quinoa starch could be used as a thickener in different formulations with the advantage of keeping a significant presence of minerals which are important to the human health.

Structural, morphological, chemical, vibrational, pasting, rheological, and thermal characterization of isolated jicama (Pachyrhizus spp.) starch and jicama starch added with Ca(OH)2.

This work focused in the study of the changes on the physicochemical properties of isolated jícama starch (IJS), and IJS added with 0.15, 0.20, 0.30% Ca(OH)2 w/w. including: the structural, morphological, chemical, vibrational, pasting, rheological, and thermal characteristics. K, Ca, Na, and P were found in IJS. X-ray patterns, which showed that nanocrystals form the IJS according to the PDF-4 simulation. The functional properties were affected by the Ca inclusion, which originated electrostatic interactions. The gelatinization temperatures shifted to high values and exhibited an unfolding. The calculation of the IR absorption coefficient (ß) of the gelatinized samples as a function of the Ca2+ for the C-OH showed that the Van der Waals interaction causes the changes in the rheological-mechanical properties. The SEM images demonstrated that starch without alkali exhibited a porous network structure, while the starch with lime exhibited flakes and porous network. The gels of Jicama starch with Ca(OH)2 showed a viscoelastic behavior (G' > G″) with a reduction of their elastic module.