## 3 Results and Discussion
### Determination of Power in the Pressing Process  
The data on power expended during the pressing process provide crucial insights into the energy efficiency of the sea buckthorn juice extraction system under various configurations. As the rotation speed increases from 140 rpm to 200 rpm, the power required for pressing correspondingly rises across all spring types. Notably, Spring 1 consistently demands the highest power expenditure at each speed, starting from 158 watts at 140 rpm and reaching up to 176 watts at 200 rpm (\(p<0.05\)). This is likely due to Spring 1's higher force exertion within the pressing chamber, which increases resistance and, consequently, the energy required to overcome it. Conversely, Spring 4 consistently exhibits the lowest power consumption, ranging from 132 watts at 140 rpm to 150 watts at 200 rpm (\(p<0.05\)) despite its ability to produce high juice yields and compression densities (Figure 10). The power consumption for each spring type shows a gradual increase as rotation speed rises, with the most significant jump occurring between 185 rpm and 200 rpm. When evaluating the influence of different springs on screw press operation, the key factor is achieving an optimal balance between the pressing force and mechanical resistance within the pressing chamber. Spring 4, despite having a lower spring force (630 N) than Springs 1 and 2, provides a more stable and appropriately calibrated pressure on the raw material. This balanced pressure ensures that the sea buckthorn berries are efficiently compressed to release juice without excessively increasing frictional resistance. As a result, the motor encounters less opposing torque, and the power consumption decreases. If the motor faces less opposing torque, it does not need to apply as much force to overcome resistance [27]. Figure 9: Change in pressure difference during sea buckthorn pressing depending on the design of pressure control spring and rotation speed (different letters above the bars indicate significant differences with increasing the rotation speed, \(p<0.05\)). Under these conditions, Spring 4 maintains a consistently high juice extraction rate because it neither under-presses (which would reduce yield) nor over-presses (which would elevate energy demand), thus achieving the highest juice yield at the lowest energy expenditure. In contrast, Spring 3 has the smallest spring force (47.5 N) and a much lighter construction. While one might assume this would save energy by minimizing resistance, it fails to maintain the required pressure threshold for efficient juice extraction. The insufficient pressing force leads to suboptimal contact between the screw and the product. Consequently, the material does not undergo uniform compression, and the motor's efficiency decreases due to irregular material flow and potential slippage. Although it requires less force initially, this lack of proper compaction and consistent mechanical loading actually leads to higher relative energy costs compared to the well-matched force provided by Spring 4. This integrated analysis underscores the necessity of considering the energy efficiency alongside the juice yield and compression density when refining pressing techniques in food engineering, ultimately contributing to more sustainable and cost-effective industrial practices. The experimental screw press we developed, incorporating various spring types and a self-regulating pressure mechanism, differs from other presses not only in its design approach but also in its methods for optimizing the juice extraction process. For example, ref. [28] focuses on adjusting the screw flight geometry to minimize raw material rotation and enhance productivity. Our press builds on this concept by using an elastic element (spring) for dynamic pressure stabilization, automatically adjusting the gap and thus reducing energy consumption. The work in [29] employs a screw jack for pressing, simplifying the construction. In contrast, our design maintains a consistently optimal pressing mode through the spring's elasticity.