## 3 Results and Discussion
### Study of Juice Yield During Pressing  
Generating the required pressure in the press compartment is directly related to the pressure control mechanism--the spring. The pressing screw moves forward and backward through a self-regulating pressure control mechanism involving a spring-loaded system, not by reversing the motor's rotational direction. As the raw material accumulates and pressure increases in the pressing zone, the tail end of the conical pressing screw compresses the spring in the pressure adjustment mechanism. This compression allows the screw to shift axially backward (toward the pressure adjustment mechanism), increasing the gap between the screw and the mesh nozzle, which reduces the pressure. When the pressure decreases, the spring expands, pushing the screw forward to decrease the gap and increase the pressure. This automatic adjustment reduces energy consumption by preventing the motor from exerting unnecessary force against high resistance. By maintaining optimal pressure levels without manual intervention or motor strain, the system enhances the energy efficiency and reduces mechanical wear, thereby decreasing the overall energy consumed during screw press operation.  
When investigating the process associated with different diaphragm holes, the minimum amount of juiciness index of sea buckthorn product in the diaphragm hole was found to be \(\delta\) = 6 mm. When the diaphragm hole is further reduced, the secreted juice and other parts of the extract side by side come out together in the mesh nozzle and cause clogging of the mesh nozzle. Therefore, the matched size of diaphragm holes, \(\delta\) = 6 mm, was selected.  
The data indicate that springs with higher maximum deformation forces generally yielded higher juice outputs (Figure 7). Specifically, Spring 4 consistently produced the highest juice yields across all rotation speeds, reaching up to 47% at 185 rpm. This suggests that a spring force of around 630 N is optimal for the mechanical pressing of sea buckthorn fruits. In contrast, Spring 3, with the lowest force of 47.5 N, resulted in the lowest juice yields, averaging around 35-41%. This underlines the importance of sufficient pressure in the pressing zone to break down fruit tissues effectively and release the juice. The rotation speed of the screw was varied from 140 rpm to 200 rpm. An increase in rotation speed is generally correlated with an increase in juice yield up to a certain point. For instance, with Spring 4, the juice yield increased from 41% at 140 rpm to 47% at 185 rpm (\(p<0.05\)). However, at 200 rpm, a slight decline to 46% was observed.  
This trend suggests that while higher rotation speeds enhance the shear forces and pressure exerted on the fruits, excessively high speeds may reduce the residence time of the fruit in the pressing zone, leading to an incomplete juice extraction. Therefore, an optimal rotation speed exists--identified here as 185 rpm--that balances the mechanical force and processing time. These results underscore the importance of fine-tuning the mechanical parameters to enhance the processing efficiency in food-engineering applications.  
\begin{table}
\begin{tabular}{c c c c} \hline
**DPPH (mg/g)** & \
\begin{tabular}{c} **Total Phenolic Content** \\ **(TPC, mg/g)** \\ \end{tabular} &
\begin{tabular}{c} \(\beta\)**-Carotene** \\ **(mg/100 g)** \\ \end{tabular} \\ \hline Methanol & 526 \(\pm\) 6 & 117 \(\pm\) 2 & 48.9 \(\pm\) 0.8 \\ Water & 363 \(\pm\) 5 & 133 \(\pm\) 2 & 48.9 \(\pm\) 0.8 \\ \hline \end{tabular}
\end{table}
Table 2: Antioxidant capacity of sea buckthorn.