The characterization of granule structural changes in acid-thinning starches by new methods and its effect on other properties

Abstract

Acid-thinned starches (ATSs) have been prepared directly from hydrochloric acid-modified corn starch. The fracture mechanism of starch granule was investigated using scanning electron microscopy combined with laser particle size analysis. And the extent of ATSs chain was also first characterized using X-ray photoelectron spectroscopy. The properties of ATS were tested by X-ray diffraction, differential scanning calorimetry, thermo gravimetric analysis, and rotational viscometry. Native starch and ATSs exhibit different structures and properties. Amorphous regions of corn starch, located in the interior of the starch granule, are preferentially hydrolyzed and can lead to starch particle fracture. The relative C=O content in the ATSs are increased, indicating that the acid thinning makes the starch molecules shorter, and the fracture extent of the starch molecular chains was 240.86 and 608.97%, respectively. Acid thinning does not change the starch crystal pattern or its basic composition, but it does increase the degree of crystallinity. Compared to the native corn starch, ATSs has a higher gelatinization temperature and a lower enthalpy of gelatinization. The acid thinning treatment drastically reduces the hot paste viscosity of the starch.

Keywords:

• acid modification
• acid thinning
• corn starch
• granule structure

Acknowledgments

This work was supported by the Fundamental Research Fund for the Central Universities (DL13CB13) and (DL12BB03). This work also gratefully acknowledges the fostering of a doctoral dissertation and the support from the National Natural Science Foundation of China (No. 31200442).