Ultrasound-microwave synergistic treatment modulates highland barley dough structure and bread quality...

Highland barley is a distinctive grain resource of the Qinghai-Tibet Plateau. However, its processing performance is restricted by an unbalanced ratio of glutenin to gliadin. In this study, ultrasound-microwave vacuum drying (USMVD) with varying microwave power (0-600 W) and ultrasonic amplitude (0-90 U) was employed to systematically investigate its effects on highland barley dough structure and bread quality. The findings demonstrated that with an increase in microwave power, the rheological characteristics, water distribution, and protein ordered structure of the dough were first improved and then deteriorated, with an optimum at 400 W. At this power, the disulfide bond content (5.38 μmol/g) and bound water proportion (93.00%) of the dough reached their maximum values. However, higher microwave power (≥ 500 W) disrupted starch chains and gluten network integrity. Similarly, with increasing ultrasonic amplitude, the dough microstructure and degree of cross-linking initially enhanced and then weakened, forming a continuous honeycomb-like network at 70 U, while higher amplitude led to network fragmentation and an elevated proportion of free water. Among all combinations, the 70 U-400 W treatment exhibited the most pronounced improvement in dough rheological properties, water distribution, protein secondary structure, disulfide bond content, and final bread quality. Collectively, USMVD can serve as an effective physical modification strategy for improving quality of highland barley-based foods.