## 3 Results and Discussions
### Vacuum Impregnation Validation and Dehydration of Apple Slices Vacuum Impregnated
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{5}{c}{**Treatments**} \\ \cline{2-5}
**Parameter** & \multicolumn{2}{c}{**Fresh Sample (Fresh Weight)**} & \multicolumn{2}{c}{**Dehydrated Sample (Dry Weight)**} \\ \cline{2-5}  & **Untreated** & *** Vacuum Impregnated** & **Untreated** & *** Vacuum Impregnated** \\  & **Sample** & **Sample** & **Sample** & **Sample** \\ \hline pH & 3.94 \(\pm\) 0.03 \({}^{\text{a}}\) & 3.26 \(\pm\) 0.02 \({}^{\text{b}}\) & 3.80 \(\pm\) 0.01 \({}^{\text{a}}\) & 3.38 \(\pm\) 0.01 \({}^{\text{b}}\) \\ Titratable acidity (\% citric acid) & 0.18 \(\pm\) 0.01 \({}^{\text{b}}\) & 0.41 \(\pm\) 0.01 \({}^{\text{a}}\) & 0.026 \(\pm\) 0.02 \({}^{\text{b}}\) & 0.032 \(\pm\) 0.001 \({}^{\text{a}}\) \\ Total soluble solids (\({}^{\text{c}}\)Brix) & 14.13 \(\pm\) 0.05 \({}^{\text{a}}\) & 10.16 \(\pm\) 0.40 \({}^{\text{b}}\) & 18.48 \(\pm\) 0.17 \({}^{\text{a}}\) & 20.05 \(\pm\) 0.30 \({}^{\text{b}}\) \\ Water activity & 0.94 \(\pm\) 0.01 \({}^{\text{b}}\) & 0.98 \(\pm\) 0.01 \({}^{\text{b}}\) & 0.36 \(\pm\) 0.01 \({}^{\text{a}}\) & 0.37 \(\pm\) 0.01 \({}^{\text{a}}\) \\ Water content (\%) & 87.90 \(\pm\) 0.22 \({}^{\text{a}}\) & 88.23 \(\pm\) 0.12 \({}^{\text{a}}\) & 6.83 \(\pm\) 1.90 \({}^{\text{a}}\) & 6.97 \(\pm\) 0.35 \({}^{\text{a}}\) \\ L\({}^{\text{*}}\) & 66.98 \(\pm\) 1.29 \({}^{\text{a}}\) & 31.38 \(\pm\) 0.79 \({}^{\text{b}}\) & 74.61 \(\pm\) 1.33 \({}^{\text{a}}\) & 39.69 \(\pm\) 1.08 \({}^{\text{b}}\) \\ a\({}^{\text{*}}\) & \(-\)2.13 \(\pm\) 0.12 \({}^{\text{b}}\) & 18.66 \(\pm\) 1.22 \({}^{\text{a}}\) & 5.01 \(\pm\) 0.86 \({}^{\text{b}}\) & 21.47 \(\pm\) 0.62 \({}^{\text{a}}\) \\ b\({}^{\text{*}}\) & 19.71 \(\pm\) 1.98 \({}^{\text{a}}\) & 19.11 \(\pm\) 0.28 \({}^{\text{a}}\) & 30.79 \(\pm\) 0.57 \({}^{\text{a}}\) & 7.73 \(\pm\) 1.52 \({}^{\text{b}}\) \\ Total soluble phenols (mg & 43.27 \(\pm\) 4.10 \({}^{\text{b}}\) & 143.17 \(\pm\) 2.72 \({}^{\text{a}}\) & 593.94 \(\pm\) 73.94 \({}^{\text{b}}\) & 855.85 \(\pm\) 80.63 \({}^{\text{a}}\) \\ Total flavonoids (mg CE/100 g) & 37.61 \(\pm\) 4.63 \({}^{\text{b}}\) & 56.04 \(\pm\) 1.52 \({}^{\text{a}}\) & 331.84 \(\pm\) 4.63 \({}^{\text{b}}\) & 525.29 \(\pm\) 28.05 \({}^{\text{a}}\) \\ DPPH (mmol TE/100 g) & 122.51 \(\pm\) 1.68 \({}^{\text{b}}\) & 230.07 \(\pm\) 3.14 \({}^{\text{a}}\) & 433.44 \(\pm\) 7.70 \({}^{\text{b}}\) & 560.49 \(\pm\) 11.34 \({}^{\text{a}}\) \\ ABTS (mmol TE/100 g) & 104.29 \(\pm\) 0.77 \({}^{\text{b}}\) & 147.99 \(\pm\) 0.70 \({}^{\text{a}}\) & 125.16 \(\pm\) 1.54 \({}^{\text{b}}\) & 150.51 \(\pm\) 1.93 \({}^{\text{a}}\) \\ \hline \hline \end{tabular} Data are presented as mean \(\pm\) standard deviation (\(n=9\)). Statistically significant differences (\(\alpha=0.05\)) among the treatments are denoted by lowercase letters in each file. L\({}^{\text{*}}\): Luminosity; a\({}^{\text{*}}\): redness/greenness; p\({}^{\text{*}}\): yellowness/blueness. \({}^{\text{*}}\) Vacuum impregnation was performed under optimal conditions from Box-Behnken design: vacuum impregnation: \(-0.4\) bar; impregnation time: 6.73 min; and restoration time: 3 min.  
\end{table} 
Table 7: Physicochemical parameters, phenolic content, and antioxidant activity of fresh and dried apple slices before and after vacuum impregnation of aqueous extracts from _Hibiscus sabkarifa_ calvces.