Fengrui Hou, Shubei Dong, Keyu Qian, Anguo Xie, Yunhong Liu
The study aimed to investigate the effects of different ultrasonic powers on the drying characteristics, moisture migration, and rheological properties of tomato pulp during ultrasound-enhanced far-infrared radiation combined vacuum drying (CUFIR-VD). The results demonstrated that with increasing ultrasound power, the drying time of CUFIR-VD was shortened by 30–120 min. LF-NMR results indicated that increasing ultrasonic power shortened free water removal by 30–90 min, while semi-bound water first increased and then decreased. SEM observations indicated that ultrasound produced a more porous surface morphology with larger and more uniformly distributed micropores. Rheological analysis indicated that ultrasound application did not change the pseudoplastic fluid nature of tomato pulp. However, the apparent viscosity increased by 17.05–130.73% after 90 min of drying as moisture removed. The storage modulus and loss modulus increased by 141.10–277.67% and 204.76–417.20%, respectively. Higher ultrasonic power caused earlier strain-hardening onset. These results confirm that ultrasound reduced drying time and promoted the transformation of the material from a liquid-like to a solid-like state. This study provides practical guidance for the application of CUFIR-VD on viscous liquid foods.