Ultrasonic Dehydration of Food Products with Moisture Removal without Phase Transition

Abstract

Introduction. Dehydration of heat-sensitive and easily oxidized food products require particular temperatures. Exposure to ultrasonic vibrations is an alternative dehydration method that presupposes moderate thermal treatment. The research objective was to identify the optimal range of sound pressure and to design a small-volume dryer. Study objects and methods. The study featured two novel ultrasonic potato dryers at t = 60 ± 1°C and a drying agent flow rate of 0.50 ± 0.03 m/s. Results and discussion. The analysis of the drying curves revealed a period of constant flow rate at a low ultrasonic exposure and its absence at a high level of exposure of ≥ 160 dB, which indicated the start of the ultrasonic dispersion process of liquid from the potato surface. The dispersion occurred due to cavitation spraying of liquid without phase transition, which significantly reduced energy consumption. As the sound pressure increased in the range from 150 to 165 dB, the drying speed increased up to 26% by 5 dB. The optimal range of the sound pressure was 160–165 dB, which optimally combined energy consumption and drying time. The research resulted in two 6 kg horizontal and vertical drum dryers that provided even ultrasonic exposure during drying. Conclusion. The convective ultrasonic potato drum dryers reduced the drying time by 44–47%.

Keywords

• heat-sensitive food
• dehydration
• ultrasonic drying rate curve
• dryers
• sound pressure
• potatoes