Application of Raman spectroscopy in structure analysis and crystallinity calculation of corn starch

In this research, acid hydrolyzed starch, B-type microcrystalline starch, and amorphous starch were prepared from natural corn starch. X-ray diffraction (XRD) and Raman spectroscopy were used to analyze the structure of these four types of starches. The Raman spectrum scattering peaks have decreased vibration wave numbers because of the changes of crystal type, and the intensity of each Raman peak is related to the size of the crystalline region. By identifying the scattering peak area in Raman spectrum as the crystalline region and the total area under the scattering curve minus the fluorescent area as the sum of the amorphous and crystalline regions, we have established a useful method for calculating the crystallinity of starch samples by Raman spectra. The comparison of results by Raman spectra with those by X-ray diffraction indicated that when the sample had high crystallinity, the difference between XRD and Raman spectrum results is small. When the sample crystallinity was low, the error of this method was only slightly larger. Therefore, Raman spectroscopy could be used as an efficient method for evaluation of the relative crystallinity of starches.