Low temperature drying process intensification by application of power ultrasound. Design and development of ultrasonic drying equipment and systems

Abstract

The application of power ultrasonics in several industrial processes has been proved to be beneficial in terms of acceleration of the process with lower energy consumption and an optimal result. Among the industrial processes that can be enhanced using power ultrasound, we can find defoaming, debubbling, particle agglomeration, supercritical CO 2 extraction, or food dehydration, among others.Focusing on food dehydration, this process consists of transferring the moisture attached to the solid matrix of the food to the external gas media, like air. This mass transfer process is influenced by two parameters: the internal and the external resistance. Internal resistance results from the characteristics of the solid matrix and temperature while external resistance mainly depends on the boundary layer thickness. Currently, convective hot-air drying (CHAD) is one of the most common and widely used drying techniques used to extend the shelf life of food products. However, this is a highly time and energy-consuming thermal process, which also negatively affects the final quality properties of the dehydrated product such as color, texture, flavor, rehydration capacity, the content of vitamins, or other nutrients.Airborne power ultrasound (APU) application in drying systems may overcome some of the limitations of CHAD by increasing the drying rate or accelerating the process even if it takes place at lower temperatures.