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

Abstract

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.