Abstract: To explore the temperature distribution and thawing time of Chinese shrimp during ultrasound-assisted thawing and the impact of the thawing process on protein denaturation, a mathematical model was established and validated to simulate the unsteady heat transfer process of ultrasound-assisted thawing by using the finite element-based commercial software COMSOL, and the changes in the structure and thermal stability of myofibrillar protein after thawing were determined. The aim is to model the ultrasound-assisted thawing process of Chinese shrimp and hence provide a basis for choosing the optimal thawing process. Results showed that the root mean square error of internal temperature of Chinese shrimp between the simulated and experimental values was 0.943 3 ℃ for ultrasound-assisted thawing, and 0.907 7 ℃ for water immersion thawing, illustrating the model to simulate the thawing process well. Ultrasoundassisted thawing could significantly improve thawing rate, and reduced thawing time by 35.9% as compared to water immersion. After thawing, the myosin heavy chain and actin did not change, but the proteins with molecular mass from 70 to 100 kDa were degraded and cross-linked to a certain degree. The maximum absorption wavelength did not significantly change, but fluorescence intensity was remarkably enhanced; the thermal stability of frozen muscle thawed by ultrasound-assisted thawing was close to that of fresh sample, while the thermal stability of frozen muscle thawed by water immersion was worsened. Overall, ultrasound-assisted thawing is an efficient thawing method that can maintain the quality of frozen Chinese shrimp.

Key words: ultrasound-assisted thawing, numerical stimulation, temperature distribution, thawing time, protein denaturation