Fine structure, crystalline and physicochemical properties of waxy corn starch treated by ultrasound irradiation

As a simple and effective physical method, ultrasound irradiation has been used to modify starch. Native waxy corn starch was treated by ultrasound irradiation at 100 and 400 W in this study. Compared with native waxy corn starch, lower proportion of B₁, B₂, and B₃, higher proportion of A chain were observed in ultrasonicated waxy corn starch. ¹H NMR combined with HPSEC-MALLS-RI data showed that lower degree of branching was observed in ultrasonicated waxy corn starch, and α-1,4 glycosidic linkages were more stable than α-1,6 glycosidic linkages in waxy corn starches. ¹³C NMR data indicated that the content of double helices was decreased, and single helix and amorphous components were increased after ultrasound irradiation. The A-type crystal structure was scarcely affected according to X-ray diffraction (XRD) analysis. The granule surface of ultrasonicated waxy corn starch became notch and rough fragment, and lower particle diameter was observed in ultrasonicated waxy corn starch. These results demonstrated that ultrasound irradiation affected chain length distribution, double helices, single helices and amorphous state, especially α-1,4 glycosidic linkages and α-1,6 glycosidic linkages, of waxy corn starch.