Some physical and thermal characteristics of amaranth starch

Starch was isolated from Amaranthus cruentus to study some physicochemical properties (swelling power, solubility, water absorption and sorption equil ibria) and compared with corn starch. Swelling power and water absorption c apacity were higher for amaranth than for corn starch, whereas the solubili ty 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 material s was above 300 m(2)/g. Gelatinization temperatures of amaranth starch meas ured by differential scanning calorimetry varied with the water/starch rati o and the heating rate. For water/starch ratios higher than 2:1, the peak t emperature was practically constant and equal to 68.3 degreesC. The enthalp y of gelatinization reached a maximum of 11.5-11.7 J/g. Two activation ener gies were found with a distinct break point at 69.2 degreesC, where rapid g elatinization of amaranth starch begins.