## 3 Results and Discussions
### Influence of Vacuum Impresation Parameters on Soluble Phenols into Apple Slices  
The influence of vacuum pressure, impregnation time, and restoration time were evaluated by applying RSM, and the ANOVA and regression coefficient outputs are listed in Table 2. Almost all independent variables and their interactions (\(X_{VP}\), vacuum pressure, \(X_{IT}\), impregnation time, and \(X_{RT}\), restoration time) were significant (\(p<0.05\)), except for \(X_{IT}\)\({}^{*}\)\(X_{RT}\) and \(X_{RT}\)\({}^{*}\)\(X_{VP}\). [PERSON] et al. [21] reported that the restoration period and the interaction vacuum period * restoration period were not significant during the vacuum impregnation of apple tissues with black carrot concentrate and explained that hydrodynamic and relaxation phenomena are related to the vacuum impregnation of solvents into vegetal tissues, but this process takes place during the relaxation period and restoration time has a significant effect on VI effectiveness. Furthermore, during the VI of grape juice into apple cubes, some factors were not significant in the model [19]. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & \multicolumn{4}{c}{**Predictors \({}^{1}\)**} & \multicolumn{4}{c}{**Response Variables**} & \multirow{2}{*}{**Relative Error (\%)**} & \multirow{2}{*}{**Impresation Degree (\%)**} \\ \cline{2-2}
**Run** & & **XVP** & **XIT** & & & & \\ \cline{3-6}  & **(bar)** & **(min)** & **(min)** & & & & \\ \hline Untreated control & & & & 34.99 \(\pm\) 0.01 \({}^{1}\) & & & & \\ T1 & \(-\)0.2 & 10 & 2 & 100.34 \(\pm\) 3.13 \({}^{\text{def}}\) & 103.86 & \(-\)3.38 & 11.72 \\ T2 & \(-\)0.3 & 10 & 1 & 113.44 \(\pm\) 1.96 \({}^{\text{e}}\) & 107.59 & \(-\)5.43 & 12.19 \\ T3 & \(-\)0.3 & 10 & 3 & 135.21 \(\pm\) 5.13 \({}^{\text{b}}\) & 134.04 & \(-\)8.27 & 13.38 \\ T4 & \(-\)0.3 & 6 & 2 & 105.73 \(\pm\) 0.99 \({}^{\text{d}}\) & 104.59 & \(-\)1.08 & 10.53 \\ T5 & \(-\)0.2 & 2 & 3 & 63.63 \(\pm\) 1.34 \({}^{\text{i}}\) & 60.11 & \(-\)5.80 & 9.31 \\ T6 & \(-\)0.4 & 2 & 2 & 68.66 \(\pm\) 1.00 \({}^{\text{h}}\) & 65.14 & \(-\)5.40 & 10.29 \\ T7 & \(-\)0.3 & 6 & 2 & 104.82 \(\pm\) 0.59 \({}^{\text{d}}\) & 104.59 & \(-\)0.21 & 10.61 \\ T8 & \(-\)0.2 & 6 & 3 & 97.05 \(\pm\) 4.25 \({}^{\text{e}}\) & 95.63 & \(-\)1.48 & 11.33 \\ T9 & \(-\)0.3 & 2 & 3 & 95.06 \(\pm\) 2.33 \({}^{\text{f}}\) & 99.16 & 4.13 & 10.74 \\ T10 & \(-\)0.4 & 6 & 3 & 142.73 \(\pm\) 1.81 \({}^{\text{a}}\) & 141.21 & \(-\)1.07 & 16.17 \\ T11 & \(-\)0.4 & 6 & 1 & 113.67 \(\pm\) 1.79 \({}^{\text{c}}\) & 115.19 & 1.31 & 11.40 \\ T12 & \(-\)0.4 & 10 & 2 & 86.51 \(\pm\) 1.22 \({}^{\text{g}}\) & 90.03 & 3.90 & 10.37 \\ T13 & \(-\)0.3 & 2 & 1 & 70.64 \(\pm\) 1.59 \({}^{\text{h}}\) & 73.58 & 3.99 & 9.53 \\ T14 & \(-\)0.3 & 6 & 2 & 103.21 \(\pm\) 0.79 \({}^{\text{de}}\) & 104.59 & 1.31 & 10.75 \\ T15 & \(-\)0.2 & 6 & 1 & 68.19 \(\pm\) 1.01 \({}^{\text{h}}\) & 69.61 & 2.03 & 10.07 \\ \hline \hline \end{tabular}  
* Data are presented as the mean \(\pm\) standard deviation (\(n=9\)). Statistically significant differences (\(\alpha=0.05\)) among the treatments are denoted by lowercase letters in each file. \({}^{1}\) Vacuum pressure (\(X_{VP}\)); Impregnation time (\(X_{TI}\)), and restoration time (\(X_{RT}\)); TSP. Total soluble phenols; \({}^{2}\) Galile acid equivalents (mg GAE/100 g wet basis), \({}^{3}\) The values were estimated using a 2 nd-order polynomial equation (R\({}^{2}=0.99\)).  
\end{table} 
Table 1: Vacuum impregnation conditions (vacuum pressure, impregnation time, and restoration time) used for response surface methodology with experimental and predicted values, error rate, and impregnation degree after impregnation of aqueous extracts of _Hibiscus subdarifa_ calves in fresh apple slices. Additionally, Table 2 shows the \(\beta\)-coefficients of the model, with most significant parameters (\(p<0.05\)), except for \(X_{T\!T}\)\({}^{*}\)\(X_{RT}\) and \(X_{RT}\)\({}^{*}\)\(X_{VP}\) interactions.