Physicochemical, structural, and rheological characteristics of corn starch after thermal-ultrasound processing

Thermal-ultrasound treatment is a green technology that can significantly alter the structural and functional properties of starches. This research extend the effect of at different temperatures (25 degrees C, 45 degrees C, and 65 degrees C) and times (30 and 60 min) on the physicochemical, structural, and rheological properties of corn starch was studied. Amylose content, solubility, swelling power, and the least gelling content increased with increasing temperature and time. Starch treated at 45 degrees C for 30 min had the lowest syneresis among all treatments. Thermal-ultrasound treatment at 25 degrees C and 65 degrees C for 60 min caused increasing paste clarity. Microscopic observations demonstrated that the starch granules were agglomerated at 65 degrees C. Although the crystallinity of samples decreased from 35.42% to 8.94%, the storage modulus was more than the loss modulus during the frequency sweep test. Pasting properties showed that pasting temperatures shifted to higher values after treatment. Nonetheless, the maximum viscosity decreased, and the final viscosity of the treated samples demonstrated that short-term retrogradation could deteriorate. Results showed that thermal-ultrasound is a viable technique for starch modification compared to conventional thermal and ultrasound treatments.