Literature review: use of ultrasound and ethanol as pre-treatment in the drying of vegetable products with bioactive compounds

Abstract

Despite the broad therapeutic action of plant species with bioactive compounds and drying being the most recommended operation for maintaining the quality of various plant materials, the fact that these materials differ in terms of moisture content, chemical composition, and morphology makes the optimization of drying methods and parameters for each species essential tools for obtaining dried plant biomass of high commercial value. The use of ethanol as a pre-treatment for drying, through immersion, allows for the modification of the product's natural structure and improves moisture transfer, consequently increasing the drying rate (KOMPANY et al., 1990). Ultrasonic waves can increase the availability of energy and accelerate mass transfer processes in the product, preserving its main qualitative attributes without significantly raising the drying air temperature (O’DONNEL et al., 2010). Therefore, this review aimed to elucidate the use of ultrasound and/or ethanol pre-treatment in the drying of various medicinal plant species, exploring their mechanisms of action and addressing their main effects on the desorption process and the chemical composition of these materials.