Scientific Study

Drying allows the obtaining of products with a long shelf life by reducing the water activity to a level low enough for the growth of microorganisms, enzymatic reactions, and other deteriorative reactions to be inhibited. Despite the benefits of this operation, the quality of heat sensitive products is diminished when high temperatures are used. The use of low drying temperatures reduces the heat damage but being the drying time longer, oxidation reactions occur and a reduction of the quality is also observed. Thus, drying is a method that lends itself to being intensified. For this reason, alternative techniques are being studied. Power ultrasound is considered an emerging and promising technology in the food industry. The potential of this technology relies on its ability to accelerate the mass transfer processes in solid-liquid and solid-gas systems. The intensification of the drying process by means of power ultrasound can be performed by modifying the product behavior during drying, using pre-treatments like soaking in liquid medium assisted acoustically or during the drying process itself applying power ultrasound in the gaseous medium. The purpose of this review is to provide a summary of the effects caused by the power ultrasound application on the quality of different dried products, such as fruits and vegetables when the acoustic energy is intended to intensify the drying process, either if the application is performed before as pretreatment or during the drying process.