# Effects of Pulsed Electric Field on Oil Extraction Rate and
## 3 Results and Discussion
### Oil Content  
The peny seed particles, prepared in Section 2.2 with three different particle sizes, underwent PEF treatment for a duration of 2 min per group, following the processing principles outlined in Section 2.1. The treated and control samples were subsequently subjected to extraction for peny seed oil using the method and procedure outlined in Section 2.3, with the oil yield being determined by employing Formula (1). The variation curves depicting the oil yield at voltages of 100 Hz and 1 kHz under different electric field intensities are illustrated in Figure 6a,b. In order to reflect the applied voltage level and effective electric field strength, the unit of electric field strength in this paper is kV/0.5 cm. The data from Figure 6a demonstrates a negative correlation between the particle size of peny seeds and the oil yield, indicating that as the particle size increases, there is a gradual decrease in oil production. For larger particle sizes, such as a 20-mesh particle size, the oil yield initially increases and then decreases with increasing electric field intensity within lower PEF range. The highest oil yield is achieved at 1 kV, which is approximately 2 percentage points higher compared to the control group. Within the high electric field range (\(>\)5 kV/0.5 cm), the oil yield gradually increases again. For a particle size of 40-mesh diameter, the oil yield gradually increases with increasing electric field intensity, and reaches its peak at 10 kV/0.5 cm (approximately 25%). This represents a 5% improvement compared to the control group. As for peny seed particles with a particle size of 60-mesh diameter, which is the smallest among them all, the oil yield shows an overall upward trend with increasing electric field intensity, and reaches its maximum value at 5 kV/0.5 cm, close to 29%. This represents an increase of nearly 12% compared to the control group. When external voltage frequency is increased to 1 kHz, similar trends in oil yield variations are observed for all three particle sizes of peny seeds as seen at 100 Hz. Further analysis was conducted to assess the statistical significance level of oil yield between the control group and the PEF treatment group, as shown in Figure 7. The statistical significance level was conducted by employing the \(t\) test in Excel software (Microsoft office 2021) with a single tail. The data for the PEF treatment group were obtained from the oil  
Figure 5: Equivalent circuit of PEF treatment unit for peny seeds: (**a**) peny seeds of different particle sizes are filled in the processing unit; (**b**) assuming that the peny seed particles are compacted into cases; (**c**) equivalent model of capacitors connected in series. Figure 6: The oil yield of different particle sizes of peny seeds with varying voltage amplitudes at 100 Hz (**a**) and 1 kHz (**b**). yield of peony seeds with the same particle size under different intensities of PEF at a constant voltage frequency. Significance level was marked using \(p\)-values, where smaller values indicate higher confidence levels and more significant results. From Figure 7, it can be seen that the PEF treatment definitely improves the oil extraction rate of peony seeds. For peony seed particles with larger particle sizes, the oil extraction rate after PEF treatment shows significant improvement compared to the control group. However, for peony seed particles with particle sizes of 40-mesh and 60-mesh, the oil extraction rate after PEF treatment was extremely significant compared to the control group. Meanwhile, comparing the oil extraction rates of peony seed particles with grain sizes of 60-mesh at frequencies of 100 Hz and 1 kHz, it can be observed that, as the voltage frequency increases, the oil extraction rate for smaller particle sizes actually decreases.