Applications of Infrared Spectroscopy in the Analysis of Ordered Structure of Starch Grain

Abstract

Fourier transform infrared spectroscopy (FTIR) is used to study the ordered structure of starch grain, which has two modes: transmittance and attenuated total reflectance (ATR). In this paper, the different deconvolution parameters of spectra were applied to compare their effects on FTIR spectra in studying the ordered structure of starch grain. The results indicated that the different deconvolution parameters had significant effects on FTIR spectra and the intensities of relative peaks. The peak half-width of 19 cm 1 and the resolution enhancement factor of 1.9 were ideal deconvolution parameters of spectra to obtain the better results. Native starches had A, B, and C three types of crystalline, their FTIR spectra showed some differences. Potato and Chinese yam starches had similar ATR-FTIR spectra, which were different from that of rice starch. However, rice and potato starches had similar transmittance-FTIR spectra, which were different from that of Chinese yam starch. The water content of sam- ple affected the spectra of ATR-FTIR, but this effect was not detected when water content exceeded 60%. The ATR-FTIR spectra showed that the hydrolysis of amorphous structure in starch grain was faster than that of ordered structure during acid treatment. The ordered degree of structure in starch grain increased with increasing time of acid hydrolysis. The amyloglucosidase hydrolysis had no significant effect on the ordered degree of structure at the outside of starch grain by the ATR-FTIR spectra, but the ordered degree of structure of whole starch grain significantly increased with enzyme hydrolysis according to the transmittance-FTIR spectra. The amylose content is an important physicochemical property in determining the starch quality. Rice starches with dif- ferent amylose contents showed the similar ATR-FTIR spectra. These results would be very useful for the application of FTIR to the analysis of ordered structure of starch grain.