The effect of ultrasonic treatment on the physicochemical and pasting properties of pre-gelatinized Coix seed starch.

Abstract

To investigate the effect of ultrasound on the cooking time of Coix seed, this study compared changes in the pasting properties of Coix seed under different ultrasonic times (0, 10, 20, and 30 min), and clarified the mechanism of ultrasound improving the cooking properties of Coix seed by analyzing the changes in starch structure and physicochemical properties. The results showed that cooking time decreased significantly as the ultrasonic time increased, with a 35% reduction in cooking time after 30 min of ultrasonic treatment compared to untreated Coix seeds. Ultrasound treatment induced the formation of visible pores on Coix seed starch surfaces. The significant increase in granule size was attributed to granule swelling and physical agglomeration caused by structural loosening. Crystallinity decreased from 27.56% to 20.41%, and the short-range order (R_1047/1022) dropped from 2.074 to 1.535. Thermal analysis revealed a reduction in gelatinization enthalpy (ΔH) from 14.82 to 13.47 J/g and a lower energy barrier for gelatinization. Regarding physicochemical properties, ultrasonically treated Coix seed starch exhibited increased solubility and swelling power, while demonstrating decreased peak viscosity and final viscosity. Furthermore, rheological measurements showed that the storage modulus (G') and loss modulus (G″) at 10 Hz decreased by approximately 34%. In conclusion, ultrasonic treatment significantly shortened the cooking time of Coix seeds, demonstrating its potential as an effective strategy for pre-gelatinization processing.