The assisting effects of ultrasound on the multiscale characteristics of heat-moisture treated starch from Agriophyllum squarrosum seeds

Present study was aimed to characterize the effects of heat-moisture treatments supported by ultrasound on structural, physicochemical and digestive properties of the starch from Agriophyllum squarrosum seeds. The starch sample was subjected to heat-moisture (120°C, 25% moisture) for different durations with assisting by pre- or post-treatment of ultrasound (20 Hz, 300 W, 20 min). A. squarrosum starch exhibited the original A-type of crystalline structure after all treatments. All modified starches had lower amylose content, amylopectin molecular weight, swelling power and solubility, and higher resistant starch content than the native starch. Heat-moisture treatments and dual modifications of heat-moisture and ultrasound increased the gelatinization temperature of starch granules and significantly (p ≤ 0.05) reduced the viscosity of starch paste. Pretreatment of ultrasound enhanced the effects of heat-moisture on the viscosity properties while post-treatment of ultrasound weakened which on the gelatinization temperature, by regulating the changes of double helix structure and short-range ordered structure in starch granules tested by Fourier-transform infrared spectrometer. Scanning electron microscopy unveiled that A. squarrosum starch pretreated by ultrasound became more susceptible to heat moisture in morphology. This work was very important for the deep excavation of the characteristics of A. squarrosum starch and the effective application of ultrasound in starch modifications.