Combined drying technology of tilapia fillets using heat pump and microwave

The technology of heat pump combined with microwave for drying Tilapia fillets was optimized by response surface method. Taking drying energy consumption and rehydration rate as dependent variable, the models were obtained by using response surface analysis of the three factors of temperature of heat pump drying, water content rate and power of microwave drying at three levels. The results of test and verification showed that all of the error between the value of models and the value of experiments was less than 5%. Base on the minimum of energy consumption, the optimized technology parameters were that the temperature of heat pump drying was 34.34℃, the water content rate at transformation point was 42.12% and the power of microwave drying was 131.69 W, respectively. Base on the maximum of rehydration rate, the optimized technology parameters were that the temperature of heat pump drying was 33.87℃, the water content rate at transformation point was 30% and the power of microwave drying was 201.43 W, respectively. Comparing the test result of heat pump combined with microwave at drying temperature of heat pump of 35℃, the water content rate at transformation point of 39% and microwave power of 252 W with that of heat pump drying test at same temperature and wind speed, it showed that the time of combination drying was shorter two-thirds than the heat pump drying. The rehydration rate of the optimized combination drying was 57.40%, and that of the heat pump drying was 39.16% at the same rehydration time of 40 min. The results also showed the rehydration rate of combined drying was increased by 46.5% compared with that of heat pump drying. The results can provide references for drying tilapia fillets of the combined heat pump with microwave drying technology.