Optimization of ultrasonic-assisted freezing of Penaeus chinensis by response surface methodology was studied in order to (1) obtain frozen Penaeus chinensis of high quality and (2) provide practical guidance for the application of ultrasonic-assisted freezing in Penaeus chinensis.

Three independent and major variables were selected, including initial ultrasonic temperature (°C), ultrasonic power (W) and ultrasonic time (s on/2 s off). On the basis of one-factor experiments, 17 groups of experiments were established by response surface methodology according to Box–Behnken design. Using multiple regression analysis the experimental data were fitted into a second-order polynomial equation, which was tested by proper statistical methods.

The optimal ultrasonic conditions were as follows: initial ultrasonic temperature 0 °C, ultrasonic power 180 W, ultrasonic time 5 s on/2 s off. Under the optimization conditions, the time of passing through maximum ice crystal generation zone was 105.500 s, which was very close to the predictive passage time of 101.541 s.

Initial ultrasonic temperature, ultrasonic time and ultrasonic power played an important role in the process of ultrasonic-assisted freezing of Penaeus chinensis. Response surface methodology was used to optimize the three factors in ultrasonic-assisted freezing, which could greatly shorten the time of passing through the maximum ice crystal generation zone and maintain the tissue structure of Penaeus chinensis well.