## 3 Results and Discussion
### Recovery of Lycopene from Tomato Peels
#### 3.1.2 Interpretation of the Response Surface Model and Contour Plot  
The response surface plots demonstrate the effects of the solid/liquid ratio (g/mL), microwave power (W), and ultrasound power (W) on the lycopene content and extraction yield (\(EY\)) of extracts obtained from tomato peels.  
Figure 3 shows three-dimensional (3D) response surface and contour plots that visually represent the relationship between the independent variables (solid/liquid ratio, microwave power, and ultrasound power) and the dependent variables (lycopene content and \(EY\)). These plots provide a clearer understanding of how variations in the independent variables impact the results.  
Figure 3a illustrates that increasing ultrasound power and reducing the solid/liquid ratio significantly increase the lycopene content. The highest lycopene content is observed when ultrasound power is in the range of 500-600 W and solid/liquid ratio is less than 0.05 g/mL. Figure 3b illustrates the influences of microwave and ultrasound power on the  
Figure 3: Response surface and contour plots showing the effects of MW power, US power, and the solid/liquid ratio on the lycopene content (mg/100 g of tomato peels). (**a**) US power vs. ratio (MW power: 200 W); (**b**) US power vs. MW power (ratio: 0.03 g/mL).  
lycopene content. As microwave power increases from 300 to 500 W, the lycopene content of the extracts is maximized, regardless of the ultrasound power is applied.  
Figure 4a,b depict the interaction effects between ultrasound power and the solid/liquid ratio, as well as microwave and ultrasound power on \(EY\). A similar trend to the lycopene content is observed for EY, as it is directly influenced by the lycopene content of the extracts obtained under various extraction conditions, since the Soxhlet method provides a constant lycopene content. Consequently, EY is maximized when the solid/liquid ratio is minimized and ultrasound power is above 500 W (Figure 4a). Regarding the influence of microwave and ultrasound power, the EY is maximum when the microwave power ranges between 300 and 500 W, regardless of the ultrasound power applied (Figure 4b).  
Based on these plots, the optimal extraction conditions for maximizing the lycopene content and EY through the synergistic application of UAE-MAE involve low solid/liquid ratios (below 0.05 g/mL) and moderate to high levels of microwave and ultrasound power (between 300 and 500 W for microwave power and between 500 and 600 W for ultrasound power). These findings from the response surface plots align with the optimum experimental conditions for lycopene extraction from tomato peels. The ideal parameters identified through experiments were a solid /liquid ratio of 0.03 g/mL, microwave power of 500 W, and ultrasound power of 600 W, resulting in a high lycopene content (37.08 mg/100 g of tomato peels) and an \(EY\) of 91.20%. Previous research on tomato waste analysis has shown that the lycopene content can range from 13.40 to 81.54 mg/100 g [30]. However, [PERSON] and [PERSON] (2014) noted that extraction yields vary widely due to factors such as the tomato variety, processing methods, by-product fraction, and extraction techniques, among others [31].