Effects of CaCO₃ treatment on the morphology, crystallinity, rheology and hydrolysis of gelatinized maize starch dispersions

Using calcium salts instead of lime allows for an ecological nixtamalization of maize grains, where the negative contamination impact of the traditional lime nixtamalization is reduced. This work assessed the effects of calcium carbonate (0.0-2.0% w/w CaCO₃) on the morphology, crystallinity, rheology and hydrolysis of gelatinized maize starch dispersions (GMSD). Microscopy analysis showed that CaCO₃ changed the morphology of insoluble remnants (ghosts) and decreased the degree of syneresis. Analysis of particle size distribution showed a slight shift to smaller sizes as the CaCO₃ was increased. Also, X-ray patterns indicated that crystallinity achieved a minimum value at CaCO₃ concentration in the range of 1% w/w. GMSD with higher CaCO₃ concentrations exhibited higher thixotropy area and complex viscoelastic behavior that was frequency dependent. A possible mechanism involved in the starch chain modification by CaCO₃ is that starch may act as a weak acid ion exchanger capable of exchanging alcoholic group protons for cations (Ca⁺²).