## 3 Results and Discussion
### Microstructural Properties of R. typhina Fruits Using SEM Analysis
#### 3.2.2 UAE Optimization Using the Response Surface Design
The composite desirability indicates that those settings are passable for the responses as a group/as one (d = 0.7719). The model proposed here shows that the highest TAC and the strongest antioxidant activity (FRAP) were obtained at a lower solvent/solid ratio, while the largest TTC was obtained at a higher solvent/solid ratio, at a solvent concentration of 45-55%. At a solvent concentration of 40-55%, the optimal TPC and TTC were found at longer extraction times of 20 and 25 min, respectively. In extracts with a higher solvent/solid ratio, the maximal responses for TTC and antioxidant activity (DPPH) were found after 25 min of extraction, while the antioxidant activity (FRAP) was greater at 20 min of extraction. In extracts with a lower solvent/solid ratio, the TAC was higher at an extraction time shorter than 15 min. The perspective plots, 3D response surface plots (Figure 5), were used to observe the influence of the independent variables on the response-dependent variables that were included in the optimization analysis (TAC, TPC, TTC, FRAP, and DPPH). This type of plot also shows the impact of two independent variables, while the third process parameter is considered constant [72]. It is observed that the anthocyanin, phenolic, and tannin contents and antioxidant activity (FRAP) decrease as solvent concentration increases at long extraction times (Figure 5(1a-4a)), while the effect on the antioxidant activity (DPPH) was opposite (5a). In more diluted extracts (higher solvent/solid ratio), anthocyanin and tannin contents were higher when medium and lower concentrations of ethanol were used (1b,3b). Regarding the concentrated extracts (lower solvent/solid ratio), high anthocyanin contents were recovered at lower UAE times (1c). Phenolics, tannins, and the antioxidant activity measured by DPPH showed higher values at longer extraction times when the solvent/solid ratio increased (Figure 5(2c,3c,5c)). On the contrary, the antioxidant activity (FRAP) presented better results for shorter extraction times when the solvent/solid ratio increased (Figure 5(4c)). A similar UAE optimization was reported by [PERSON] et al. (2014) [32], but only with regard to the antioxidant activity by DPPH on _R. typhina_ fruit extracts under different experimental conditions (liquid-to-solid ratio, concentration of ethanol, pH, extraction time, and temperature); their results showed that DPPH values increase as the solvent/solid ratio increases. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Response** & **Target** & **Predicted Responses** & **Desirability** & **Composite Desirability** & **Optimal Values for Factors** \\ \hline _Y1_ & Maximization & 29.2151 & 0.7010 & & \\ _Y2_ & Maximization & 1698.0266 & 0.9547 & & X\({}_{\text{Sc}}\) = 61.5152\% \\ _Y3_ & Minimization & 1430.4662 & 0.7896 & 0.7719 & X\({}_{\text{T}}\) = 10 min \\ _Y6_ & Maximization & 848.0085 & 0.9220 & & X\({}_{\text{R}}\) = 20/1 (\(v/w\)) \\ Y7 & Maximization & 88.2253 & 0.5565 & & \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Optimal values from UAE optimization indicating the target for parameters.