The effect of Ca2+ ions on the pasting, morphological, structural, vibrational, and mechanical properties of corn starch-water system

This work focuses on the effects of different concentrations of Ca2+ ions 0, 0.10, 0.15, 0.25, and 0.35% w/w and the steeping time in corn starch-water system with and without heating, as well as the influence of the Ca2+ concentrations on the pasting profile, regarding the physicochemical changes that take place along the thermal process. The first and second derivatives of the pasting profiles were calculated to identify the main changes originated in the heating and cooling regions. The inclusion of Ca2+ ions has a strong effect at the end of the pasting profile; below the gelatinization temperature starch grains exhibit a semi-crystalline structure and were still integer, at the peak viscosity, the samples were amorphous as a result of the gelatinization, at the final viscosity the structure was complete amorphous observed in the X-ray patterns. Micrographs of the starch-water system with Ca2+ show that the morphology changed rapidly and depends on the Ca2+ concentrations. IR spectroscopy shows that Ca2+ions did not form any new chemical bonds, yet only the van der Waals interaction occurred. We demonstrate for the first time the effect of calcium ions on the elastic and plastic regions of the custard and hydrogels.