Effect of dual-frequency ultrasonic vacuum drying on drying characteristics and quality of honey

The effect of dual-frequency ultrasonic vacuum drying technology on viscous materials has not been studied. Therefore, in this research, the effects of two (28 + 28 kHz, 40 + 40 kHz) dual-frequency ultrasonic vacuum drying methods on the drying characteristics and quality of honey were investigated using ultrasonic power, vacuum and temperature as one-factor experiment. Results showed that ultrasonic power was the main drying factor, followed by vacuum degree, and temperature. Among the six models, the Logarithmic model was the most accurate one to describe the change rule of honey moisture during the ultrasonic vacuum drying process. Drying temperature and ultrasonic power were the main factors that affected the change of sugar composition and hydroxymethylfurfural (HMF) content in honey. Meanwhile, the color of honey after drying was darkened, the hardness was increased, while the viscosity was reduced. In summary, the optimal ultrasonic drying combination was 28 + 28 kHz ultrasonic frequency, 80 W ultrasonic power, −90 kPa vacuum degree and 30 °C temperature. This research provides essential information for equipment improvements for ultrasound in food processing and for future research on viscous materials. • Dual-frequency ultrasonic vacuum drying technology increased the drying rate. • Frequency 28 + 28 kHz, power 80 W, vacuum degree −90 kPa, temperature 30 °C was optimal. • Logarithmic model predictions were accurate. • Honey has decreased reducing sugar content, increased HMF content, darkened color, hardened, and decreased viscosity.