## 1 Introduction  
Carrot is one of the most widely grown root vegetables around the world. Consumption of carrots and carrot products is constantly increasing due to their richness in natural nutrients, including carotenoids or dietary fibre [1, 2]. Apart from being consumed in a fresh form, the root is usually dried to extend the shelf life. The most commonly used convective drying is a thermal process of simultaneous heat and mass exchange, the purpose of which is to evaporate some of the water from the material into the surrounding air, which is both the medium providing heat and carrying moisture away from the material. In general, the aim is to ensure the microbiological stability of the food, which results in a significant slowing down of many chemical reactions and even elimination of enzymatic changes in the dry material [3]. The drying of vegetables is predominantly carried out by the means of the convective method due to its simplicity, ease of process control and low costs of such dryers [4]. The disadvantages of this method, however, include high energy consumption and relatively low quality of the dried product, in particular low rehydration ability, high shrinkage and high losses of nutrients [5; 6; 7]. Considering the further use of dried carrot as a component of, e.g., instant soups, seasoning mixes, etc., it is especially important to select a processing method to provide a product characterizing by a good rehydration ratio, high content of carotenoids and stable colour. Therefore, novel pre-treatment methods are sought in order to reduce the negative aspects of convective drying. One of such types of innovative processing is the use of ethyl alcohol as a dehydrating substance, using it either during pre-treatment or during the drying process (drying in an ethanol atmosphere). In principle, such enhancement of drying is to shorten the drying time and also to increase the rehydration capacity and reduce the degradation of chemical compounds. Literature indicates that the use of ethanol in the drying process shortened the drying time and allowed for obtaining a product of high quality with a simultaneous large loss of water from the tissue and thus a better structure [8; 9; 10]. Ethanol is an organic solvent that is able to extract some components of cell walls and membranes, e.g., polyphenols, lipids, or proteins and which maintain the cellulose, pectin, lignin, or hemicellulose in the cell wall. Thus, the thickness of the cell wall may be reduced and the permeability may increase [11; 12]. Considering also that ethanol has both a lower boiling point and surface tension than water, and the fact that ethanol mixes with the aqueous solution on the surface of material, which increases the vapour pressure as well as the Marangoni effect, the heat and mass transfer processes are accelerated [13; 14]. [PERSON] et al. [15] reported that the most effective matter in reducing the drying time was to spread the ethanol over the material in a thin layer than to dry in an ethanol atmosphere. These preliminary studies have become a precursor to the use of ultrasound during immersion in ethanol as a pre-treatment [11; 9; 16; 17; 18]. Ultrasound (US) is pressure wave causing vibration of air in the frequency range inaudible for humans--from 18 kHz to 100 MHz. This mechanical wave may be propagated through liquid or solid media by the means of series of alternating compression and rarefaction [19; 20]. The high intensity ultrasound (from 18 up to 100 kHz) is used for modification of tissue structure (by disruption of the cells and microscopic channels' formation) and acceleration of mechanical or mass and/or heat transfer processes [21; 22; 23; 24; 25]. These effects can be obtained due to \"sponge effect\", cavitation phenomenon and the effects accompanying cavitation, such as microstreaming or release of fountain of microbubbles [19]. Nowadays, the simultaneous pre-treatment in ethanol with the application of ultrasound has been studied, which may bring the benefits of both pre-treatments.