Evaluation of starch retrogradation by infrared spectroscopy

Starch is an important component of food, and starch retrogradation is a common phenomenon during the storage of starch-based foods. In this study, the retrogradation process was investigated using Fourier transform infrared spectrometer (FTIR). The relationship between the change in the ratio of 1047 cm−1/1022 cm−1 (R1047/1022), and storage time, and changes in hydrogen bonds was studied. With the extension of storage time, the value of R1047/1022 increased. Moreover, at the early (0–7 days) and late (7–35 days) stages, the storage time and the R1047/1022 showed a good linear correlation. The retrogradation degree measured by FTIR was consistent with that obtained from differential scanning calorimetry, and the crystallization kinetics conformed to the Avrami equation. Furthermore, the second derivative of infrared spectroscopy was used to study the changes in hydrogen bonds. With the extension of the retrogradation time, the distance of inter-strand hydrogen bond and inter-double helices hydrogen bond decreased, and the bond energy increased. These results suggest that FTIR, as a simple and fast analytical method, can be used as a means to evaluate the degree of starch retrogradation from the perspective of hydrogen bonding and short-range order.