A new method for determining the relative crystallinity of chickpea starch by Fourier-transform infrared spectroscopy

• A FT-IR method is developed to determine the relative crystallinity (RC) of starch.
• There is a holocrystalline-peak (HCP) in FT-IR spectra of starch.
• The HCP can be divided into amorphous region and crystalline region.
• The RC of starch is the ratio of the area of crystalline region to the area of HCP.
• The RC of starch determined by FT-IR is in agreement with that determined by XRD.

A new method for determining the relative crystallinity (RC) of chickpea starch was developed by using Fourier-transform infrared (FT-IR) spectroscopy, based on hypotheses as described as follows: there is a Gaussian holocrystalline-peak (HCP) in the 800–1300 cm−1 region of FT-IR spectrum of starch which is divided into amorphous region and crystalline region; the crystalline region of HCP is the overlap of the HCP and the FT-IR spectrum of starch; the RC of starch is the ratio of the area of crystalline region to the area of HCP. It was found that there was no significant difference between the RC determined by FT-IR method and that determined by X-ray diffraction (XRD) method. The intra-class correlation coefficient was 0.998 (p = 0.000, n = 9) and the 95% confidence interval was 0.992–1.000 for the RC determined by XRD and FT-IR. Furthermore, the developed method showed good repeatability (coefficient of variation (CV), 1.1–2.9%) and good intermediate precision (CV, 2.8%).