## 3 Results and Discussion
### Changes in Raw Material Caused by Pre-Treatment in Ethanol Solution with and without Ultrasound

Table 1: Relative mass change (\(\Delta\)m) of carrot slices (%) in relation to the initial weight, dry matter content and water activity changes of carrot tissue pre-treated without and with ultrasound; error bars indicate \(\pm\) SD (standard deviation calculated from four repetitions in the case of relative mass change and six repetitions in the case of dry matter content and water activity). In fresh carrot (untreated), the dry matter content was 9.70 \(\pm\) 0.79% (Table 1). Both in the case of EtOH and EtOH+US treatments, the dry matter content of carrot slices in most cases increased after treatment. The increase was of up to 27 and 19% for samples treated in ethanol alone and in ethanol with the application of ultrasound, respectively. The two-way analysis of variance did not reveal a significant influence of type nor time of treatment (Table 1). Additionally, [PERSON] et al. [26] observed an increase in dry matter content in scallion slices, when the immersion in ethanol was applied, and with the assistance of sonication the value even increased. Changes in the dry mass content are related to two opposite phenomena: the penetration of solvent into the material and dry matter components into the environment [35; 36]. In the case of the current research, the ultrasound treatment was carried out in ethyl alcohol, which allowed to obtain the desired effect, i.e., increasing the dry substance content, and thus water loss as a result of its partial, surface replacement by alcohol. In the case of water activity, all samples did not differ significantly, however, the two-factor analysis of variance showed the existence of a statistically significant effect of the type of pre-treatment on the value of water activity in the material after treatment (\(p<0.05\); Table 1). Higher values were obtained in the case of EtOH+US in comparison to the EtOH sample. The conductivity of the ethanol solution after carrot pre-treatment with ultrasound (EtOH + US), depending on the ultrasound frequency (21 and 40 kHz), in comparison with the conductivity of the EtOH samples, is presented in Figure 1. This method of measurement is mainly used to assess the properties of food products, their origin, quality after pre-treatment, e.g., by evaluating tissue leakage after the blanching process [20]. Ethyl alcohol, thanks to its properties, helps to extract substances from plant material. In carrot tissue ethanol positively influenced extraction, especially of the substances with hydroxyl groups in their structure [37]. Thus, the measurement of the electrical conductivity of ethanol used during the pre-treatments allows the assessment of the degree of leaking out of dissociating compounds from the carrot tissue. The conductivity of pure ethanol was 0.75 \(\pm\) 0.10 \(\upmu\)S/cm. A significant (\(p<0.05\)) effect of both the treatment type and time on the conductivity of the ethanol solution was proven (Figure 1). During all pre-treatments, the electrolyte losses from the plant material to the surrounding medium was most intense in the first 5 s. With longer pre-treatment,  
Figure 1: Conductivity of the ethanol solution after carrot pre-treatment without and with ultrasound (21 and 40 kHz): a, b, etc.—different letters indicate different homogeneous groups (one-way ANOVA, \(\alpha\) = 0.05). increasing conductivity was observed, especially when ultrasound frequency of 40 kHz was used. In the case of EtOH+US 21 and EtOH samples, the conductivity values were similar in almost the entire process. It means that the use of a higher frequency and longer time caused the higher compounds to leak from the carrot tissue. The different influence of the two types of US frequencies proves the need to select processing parameters for a given material. Ultrasound causes the phenomenon of cavitation, as a result of which there is a local increase in pressure and temperature in the material, which destroys the structure of plant tissue cells, making it easier for substances to leak from the tissue [38,39].