Assessment of order of helical structures of retrograded starch by Raman spectroscopy

Abstract

In this study, the long- and short-range order of retrograded starch was evaluated using Fourier-transform infrared spectroscopy (FTIR), wide-angle X-ray diffraction (XRD), and Raman spectroscopy. FTIR and XRD could not assess the degree of order of various helical structures. Raman spectroscopy was used to establish a method for evaluating the order of the helical structures of the retrograded starch. The characteristic peaks of the Raman bands around 865, 1343, and 2908 cm −1 were related to the amylose double helix, amylose single helix, and amylopectin double helix, respectively. The full width at half maximum (FWHM) of the characteristic peaks was used to assess the order of the helical structure. During retrogradation, the order of all helical structures increased, which was greater for the amylose double helix than that of other helical structures in the early stage of storage. The crystallization rate of the amylose double helix was also higher than that of other helical structures. • A method for assessing the order of helical structures was established. • The order of all helical structures increased during starch retrogradation. • Crystallization rate of various helical structures were obtained.