## 3 Results and Discussion
### Optimisation of the Processing Parameters
The lowest predictive capacity value was obtained for the FRAP\({}_{2}\) model, which was 77.49%, and the highest was for the ABTS\({}_{2}\) model, which was 91.39%. A better correspondence between the predicted and experimental responses can be partly explained by the number of parameters present in the analysed models. An analysis of the results showed a significant influence of the diameter of the extraction vessel on the course of the extraction process. For the vessel with a diameter of 35 mm, there is a faster increase in the efficiency and antioxidant activity of the extracts at lower levels of ultrasound amplitude compared to the vessel with a diameter of 25 mm. This phenomenon can be explained by the distance between the ultrasonic probe and the bottom of the vessel. For the reactor with a diameter of 35 mm, this distance is 20 mm, and for the reactor with a diameter of 25 mm, this distance is 75 mm. As a result, the flux of cavitation bubbles in the case of the first vessel is closer to the extracted material, which results in more intensive disintegration of solid particles and higher kinetics of the polyphenol extraction. Further increases in the ultrasound amplitude cause only a slight increase in the concentration of the extracted substances due to its decreasing concentration in the raw material. In the case of the vessel with a diameter of 25 mm, the distance between the ultrasonic probe and the extraction bed is much greater, which results in a weaker impact of the cavitation flux and thus slower extraction kinetics. Increasing the ultrasound amplitude causes a higher cavitation flux and accelerates the extraction kinetics. As a result, the final values of polyphenol yield at the maximum time do not differ much between the individual diameters of extraction vessels. Similar observations regarding the influence of the position of the ultrasonic probe on the extraction efficiency were made by [PERSON] et al. [17]. The all-trans-\(\beta\)-carotene extraction efficiencies with a 2 cm and 12 cm distance between the ultrasonic probe and the raw material were, respectively, 84.5% and 12.3% higher than the extraction efficiency obtained during maceration. [PERSON] et al. [18] analysed the effect of the vessel diameter and height on the ultrasonic extraction efficiency of mangiferin from _Mangifera indica_ leaves. The experiment was carried out for four different vessel depths (inside the ultrasonic bath), i.e., 1.016, 2.54, 5.08, and 7.62 cm. The highest extraction efficiency was obtained at a depth of 2.54 cm. The next stage of the experiment was carried out for different vessel diameters: 1.3, 1.5, 2.5, 3, 3.5, 5, and 7 cm. The authors showed that with the increase in the diameter of the extraction vessel, the extraction efficiency increased up to a certain limit, after which it remained constant. In vessels with a diameter of 1.3 cm, the yield of mangiferin was 26 mg/g, while in vessels with diameters of 3.5, 5, and 7 cm, the yield was approximately 31 mg/g [18]. A very interesting finding in this work is also a different effect of alcohol concentration on the course of the extraction process for individual extraction vessels. In the case of the vessel with the larger diameter (35 mm), an initial increase in the extraction efficiency occurs with increasing alcohol concentration in the solvent, and then, after exceeding the concentration of the solvent, the extraction efficiency decreases by about 60%. In the case of the extraction vessel with the smaller diameter (25 mm), the highest values of efficiency and antioxidant activity of the extracts were observed in the range of 30 to 50% alcohol, and further increasing the alcohol concentration resulted in a rapid decrease in the measured values. This suggests that the increase in alcohol concentration with increasing distance from the extraction bed contributes to a decrease in the extraction efficiency.