Impact of Ultrasound on the Physicochemical and Structural Properties of Gluten Protein During Controlled Thermal Treatment

Gluten proteins are widely used in the food processing industry, but their low purity, poor water solubility, and limited thermal stability restrict broader applications. Ultrasound is a non-thermal physical technique that can modify protein functionality; however, its effects on gluten proteins during thermal processing remain insufficiently quantified. Therefore, in this study, ultrasound intensity (60, 90, and 120 W/L) combined with controlled thermal treatment (30, 55, and 80 °C) was systematically evaluated in a simplified gluten model system, providing direct evidence of ultrasound-induced alterations in intermolecular forces and structural properties. Ultrasound treatment facilitated the removal of starch and other non-protein components from the gluten aggregates, as evidenced by protein content increasing from 85.47% in the untreated control to 87.73% in the sample treated at 120 W/L and 30 °C, accompanied by a decrease in starch content from 3.52% to 1.84% (p < 0.05). The water absorption index increased significantly with increasing ultrasound intensity, reaching 2.95 g/g at 120 W/L and 30 °C compared with 2.80 g/g in the untreated control (p < 0.05); however, the solubility index decreased from 3.75% to 2.77% (p < 0.05). In addition, thermal weight loss increased and the degradation temperature decreased significantly after ultrasound treatment at 30 and 55 °C (p < 0.05), while no significant change was observed at 80 °C. Chemical interaction analysis also revealed that ultrasound disrupted hydrogen bonds and increased the free sulfhydryl content, suggesting a possible alteration of the disulfide bond balance. Collectively, these findings suggested that ultrasound modulated the functional and structural characteristics of gluten proteins by affecting noncovalent/covalent interactions and protein–matrix associations. Thus, ultrasound represents a promising and feasible approach for the targeted modification of gluten proteins in food processing applications.