Effect of long-term retrogradation on the crystallinity, vibrational and rheological properties of potato, corn, and rice starches

Starch retrogradation remains as an area of interest due to its technological implications. The long-term structural changes taking place during the retrogradation process of gels from rice, potato, and corn starches were investigated using X-ray diffraction (XRD), rheology, and Fourier transform infrared spectroscopy (FTIR). Rietveld refinement of XRD showed that initial crystalline arrangement of starches transitioned to a combination of hexagonal and monoclinic structure in varying proportions, also the distribution of crystalline and amorphous phases had a preferential growth depending on the starch source. Final crystallinity values after 28 days in gels were potato (12.38 %) > corn (7.26 %) > rice (1.92 %). All starch gels showed a viscoelastic behavior with a mesh size of the gel network decreasing over time. FTIR showed a close relationship with crystallinity growing. These results enhance the understanding of structural changes in starch gels during retrogradation and help predict their behavior.