Physicochemical and structural properties of starches isolated from quinoa varieties

Starches isolated from four quinoa varieties were analyzed for physicochemical, morphological, and structural properties. All varieties of quinoa starches (QS) have lower amylose content, ranging from 9.43% to 10.90%, than maize starch (22.58%) and potato starch (17.75%) and thus has lower water solubility index and higher swelling power. QS has lower pasting temperature and setback and breakdown than maize starch. QS has lower enthalpy change (Delta H) and exhibits good resistance to retrogradation. In terms of rheological properties, QS has lower degree of shear-thinning and thixotropy than maize and potato starch. Additionally, QS has irregular polygon granules with small granule diameters ranging from 1.21 mu m to 1.95 mu m and display the A-type X-ray diffraction pattern. The crystallinity of QS ranges from 21.00% to 29.67%, which is significantly lower than that of maize starch. Fourier-transform infrared spectroscopy showed that the QS structure is a double helix and has a lower degree of order than the structures of maize and potato starch. This study revealed the particular properties of QS with four varieties as compared with other starch varieties.