Ultrasound treatment of maize starches with varying amylose and gelatinisation state

To elucidate how ultrasound affects starch architecture, starches with varying amylopectin/amylose ratios and pre-gelatinised states were systematically investigated. Waxy maize starch (WMS, 1% amylose), normal maize starch (NMS, 26% amylose), and Gelose 80 (G80, 80% amylose) were pre-conditioned to non- (A: 50 °C), semi- (B: 65 °C/85 °C), and fully gelatinised (C: 95 °C/140 °C) states prior to sonication (20 kHz, 1 h, 2250 J/cm³). Multi-scale structural characterization, spanning granular to molecular levels, was performed using mastersizer, polarised light microscopy, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), Nuclear Magnetic Resonance (NMR) and size-exclusion chromatography (SEC). Ultrasound promoted granule disruption and amylopectin dispersion, accompanied by significant reductions in gelatinization enthalpy (ΔH), relative crystallinity (RC), SAXS peak intensity (q ≈ 0.07 Å^-1), and double-helix content. In contrast, crystalline polymorphism, single-helix content, and molecular size distribution remained largely unchanged. These findings reveal selective ultrasound-induced modulation primarily targeting amylopectin double helices, with structural susceptibility dictated by amylopectin architecture and granule integrity.