Ultrasonic modification of lotus starch based on multi-scale structure: Pasting, rheological, and thermal properties

Abstract

The modulation mechanism of ultrasound on starch physicochemical properties is unclear which limits the application of ultrasound in starch. This study investigated the effect of ultrasound treatment (UT) on pasting, rheological, thermal properties, and multi-scale structure of lotus starch. After 270 W UT, the peak and final viscosity was 2.23 and 2.64 times that of native starch. Whereas, the pasting viscosity decreased under 360 and 450 W UT. UT increased the viscoelasticity of LS, however, the viscoelasticity decreased after 360 and 450 W UT compared with those under a UT power of 270 W. Electrostatic interaction and hydrogen bonding intensified after UT compared with native LS. Some pores appeared on the surface of starch granules and increased with the increase of ultrasound power. Lamellar thickness initially increased from 10.03 nm to 10.26 nm and then decreased to 9.81 nm when the UT power exceeded 270 W. The ordered aggregate structure of starch loosened, while the short-range ordered structure strengthened after UT. The amorphous region expanded, double helices became ordered and compact, and entanglement between starch granules enhanced after UT. This study provided a promising approach to achieve starchy products with suitable quality through understanding multi-scale structure changed via UT.