## 3 Result
### Testing and Evaluation of Sorting/Ejection Equipment for Foreign Object Removal
#### 3.3.2 Multi-Group Quick-Frozen Material Removal Testing  
To verify the optimal quick-freezing temperature proposed in this study for raisins adhered with foreign objects, which aims to effectively remove foreign objects while maximizing the removal ratio of the sorting system, multiple sets of quick-freezing experiments at different temperatures were conducted for systematic sorting validation.  
The detailed testing procedure is as follows: First, bulk materials were divided into seven groups and subjected to quick-freezing at target temperatures of 0 \({}^{\circ}\)C, \(-\)10 \({}^{\circ}\)C, \(-\)20 \({}^{\circ}\)C, \(-\)30 \({}^{\circ}\)C, \(-\)40 \({}^{\circ}\)C, and \(-\)50 \({}^{\circ}\)C. Subsequently, each group of materials was sequentially placed into the sorting device for separation, sieving, and precision sorting. Finally, under different quick-freezing temperature conditions, critical parameters were statistically analyzed, including number of raisin particles without adhered foreign objects in the receiving box, number of raisin particles still adhered with foreign substances, number of damaged raisin particles, quantity of foreign objects entering the raisin collection zone, and quantity of raisin particles entering the foreign object collection zone. Based on these statistics, separation rate, breakage rate, residue rate, removal rate, and removal ratio were calculated, as shown in Figure 30. Through comprehensive comparative analysis of all statistical data, the effectiveness of the proposed optimal quick-freezing temperature was validated.  
By comparing the evaluation index data under different quick-freezing temperatures, it can be observed that as the freezing temperature decreases, the separation effect between raisins and adhered foreign objects exhibits a distinct trend. When the freezing temperature gradually decreases from 0 \({}^{\circ}\)C, the separation rate increases progressively, peaking at 93.76% at \(-\)40 \({}^{\circ}\)C, after which it remains relatively stable despite further temperature reduction. This indicates that within the low-temperature range around \(-\)40 \({}^{\circ}\)C, freezing treatment significantly weakens the adhesion force between raisins and foreign objects,  
Figure 30: Comprehensive Evaluation Metrics under Different Quick-Freezing Temperature Conditions.  
thereby enhancing the separation rate. Meanwhile, the breakage rate gradually decreases with temperature reduction, reaching 3.05% at \(-40\)\({}^{\circ}\)C before stabilizing. Residue rate and removal rate data demonstrate that moderate freezing temperature reduction effectively reduces foreign object residue on raisins, though excessively low temperatures may adversely affect the residue rate (e.g., a 2.12% increase at \(-50\)\({}^{\circ}\)C compared with \(-40\)\({}^{\circ}\)C). The integration of visual and precision removal modules ensures removal rates above 89% across all tested temperatures, with the highest value of 94.52% achieved at \(-50\)\({}^{\circ}\)C. At \(-40\)\({}^{\circ}\)C, the carry-over ratio reaches 71:1, indicating low mis-removal rates and high removal accuracy at this temperature. Based on comprehensive analysis of all indicators, \(-40\)\({}^{\circ}\)C emerges as the optimal freezing temperature within the tested range, effectively removing foreign objects while minimizing raisin loss, thereby validating the effectiveness of the optimized freezing temperature and separation method.