Some physical and thermal characteristics of amaranth starch Algunas propiedades físicas y térmicas del almidón de amaranto

Abstract

Starch was isolated from Amaranthus cruentus to study some physicochemical properties (swelling power, solubility, water absorption and sorption equilibria) and compared with corn starch. Swelling power and water absorption capacity were higher for amaranth than for corn starch, whereas the solubility of amaranth starch was, in comparison, lower. The adsorption capacity at monolayer value of both starches was practically coincident. However, the sorbed water at monolayer seemed to be more firmly adsorbed in corn than in amaranth starch. The specific surface area of adsorption for both materials was above 300 m2/g. Gelatinization temperatures of amaranth starch measured by differential scanning calorimetry varied with the water/starch ratio and the heating rate. For water/ starch ratios higher than 2:1, the peak temperature was practically constant and equal to 68.3 °C. The enthalpy of gelatinization reached a maximum of 11.5-11.7 J/g. Two activation energies were found with a distinct break point at 69.2 °C, where rapid gelatinization of amaranth starch begins.