New ultrasonic technologies for food drying process intensification

Food dehydration processes assisted by power ultrasound constitute a new, efficient and green technology. In order to obtain good results with this technology it is necessary to take into account several aspects regarding the ultrasonic generation, the energy propagation and absorption in the samples. Ultrasonic waves produce different effects when propagating through a medium, like an increase in mass transport kinetics by accelerating these kind of processes, and others related to the so called sponge effect and cavitation. This kind of processes needs the whole system to work in a high-power regime. This may imply the appearance of non-linear effects in the transducer behaviour and in the acoustic field generated inside the dehydration chamber. The aim of this work is to describe this technology, capable of producing permanent changes in the samples treated, considering the design and characterization of high-power ultrasonic transducers, the generation and performance of the high-intensity ultrasonic field and the ultrasonic effects produced in the samples, and paying especial attention to those non-linear effects that may appear and its influence on the global behaviour of the whole system.