28Low temperature air drying involves temperatures below or close to the freezing point 29 and aims to reduce the water content or to remove organic solvents keeping quality 30 attributes, thus it has a great potential in food, chemical, pharmaceutical and cosmetic 31 industries. Depending on the temperature and solvent involved, the removal is by 32 evaporation or sublimation, but in all cases, the drying process is slow due to the low 33 temperature used. An efficient ultrasound application at atmospheric pressure and 34 moderate temperatures could accelerate the drying process. Thus, the main aim of this 35 work was to test the feasibility of power ultrasound to intensify low temperature drying 36
processes. 37Drying kinetics of carrot, eggplant and apple cubes (side 10 mm) were carried out at 38 atmospheric pressure, 2 m/s, -14 ºC and relative humidity 7% with (acoustic power 39 19.5 kW/m 3 ) and without ultrasound application. At the same experimental conditions, 40 kinetics of ethanol removal from a solid matrix were also performed. Diffusion models 41 were used to describe drying curves and identify kinetic parameters in order to 42 evaluate and quantify the process intensification attained by ultrasound application. 43The effect of ultrasound application was similar for all products tested, being drying 44 time shortened between 65-70 %. In the case of ethanol removal, the time reduction by 45 ultrasound application was even higher achieving 120 %. Both, effective moisture 46 diffusivity and mass transfer coefficient increased from 96 to 170 % and from 407 to 47 428 % when ultrasound was applied, respectively. Therefore, ultrasound application 48 should be considered a potential and effective technology to intensify low temperature 49 drying processes, being capable to make more affordable and less energy and time-50 consuming these processes for all kind of industries.