## 3 Results and Discussion
### pH  
Figure 5 shows the influence of input variables on the pH value for two extraction vessels with diameters of 35 and 25 mm. Based on the analysis of the graphs, it can be concluded that the time and amplitude of the ultrasound do not change the pH value. The alcohol concentration changes the acidity of the obtained extracts. After an increase in alcohol concentration, the obtained extracts were characterised by a lower level of acidity (higher pH value). This indicates that changes in the concentration of alcohol in the solvent affect the extraction efficiency of individual polyphenols. This is due to the different polarities of the phenolic compounds. For example, succinic acid found in mountain ash is more soluble in ethanol than in water. In turn, some flavonoids, such as quercetin or rutin, are considered almost insoluble in water; they dissolve better in ethanol [32]. Our assumptions were indirectly confirmed by the results obtained by other authors [33,34]. The effect of ethyl alcohol concentration on the content of individual polyphenols in extracts was observed by [PERSON] et al. [33]. The gallic acid content during a high pressure and temperature extraction of polyphenols from grap marc was 69.57 mg/100 g using 100% ethyl alcohol and 105.25 mg/100 g using water as solvents, respectively. However, for ultrasound-assisted extraction, the gallic acid content was higher when ethyl alcohol was used as a solvent. The effect of the ethyl alcohol concentration on the percentage of individual polyphenols in propolisis extracts was also observed by [PERSON] et al. [34]. In extracts obtained using water, 15 phenolic compounds were found, and in extracts obtained using a 75% solution of ethyl alcohol, 28 phenolic compounds were found. In the case of water, 60% of phenolic compounds were phenolic acids, and in the case of the 75% alcohol solution, 80% were flavonoids and phenolic acid esters. A higher content of phenolic acids obtained with the use of an alcohol with a lower concentration will increase the acidity (lower the pH) of these extracts. \begin{table}
\begin{tabular}{l l l l l l l} \hline \hline
**Source** & **Sum of Squares** & **DF** & **Mean Square** & _F-Value_ & _p-Value_ & \\ \hline Model & 14,306.22 & 4 & 3576.55 & 56.82 & \textless{}0.0001 & significant \\ \(X_{1}\) & 1616.18 & 1 & 1616.18 & 25.68 & 0.0005 & \\ \(X_{2}\) & 3875.95 & 1 & 3875.95 & 61.58 & \textless{}0.0001 & \\ \(X_{3}\) & 5914.16 & 1 & 5914.16 & 93.96 & \textless{}0.0001 & \\ \(X_{3}^{2}\) & 2899.92 & 1 & 2899.92 & 46.07 & \textless{}0.0001 & \\ \hline Residual & 629.45 & 10 & 62.94 & & & \\ \hline Lack of Fit & 593.49 & 8 & 74.19 & 4.13 & 0.2097 & not significant \\ \hline Pure Error & 35.96 & 2 & 17.98 & & & \\ \hline Total & 14,935.67 & 14 & & & & \\ \hline \hline \multicolumn{7}{l}{\(R^{2}=0.9579\), adj \(R^{2}=0.9410\), CV = 10.51, Adeq Precision 24.73} \\ \hline \end{tabular}
\end{table} 
Table 9: Effect of the independent variables on the dependent variables and statistical significance for \(ABTS_{2}\) of extracts obtained in vessels with a diameter of 25 mm. In order to confirm the significance of the influence of the tested input variables on the pH value, a statistical analysis was performed. The findings of this examination are displayed in Tables 10 and 11. It can be seen that for both models, only the linear effect of the alcohol concentration had a significant effect on the pH value. Both the first and the second equation were validated correctly, which is evidenced by low probability coefficients (\(p\) < 0.0001; \(p\) < 0.0001) and the lack of fit of the model (\(p\) = 0.1795 and \(p\) = 0.1990). The high values of the determination coefficient \(R^{2}\) (0.9930 and 0.9920) and the adjusted coefficient \(R^{2}\) (0.9924 and 0.9913) indicate that the scatter of the data around the regression lines is very low. The low