## 4 Discussion
The overall best results were aligned with the high extraction yield (\(W_{s}=\) 10 kJ/kg, \(t_{dist}=\) 1:30 h), lowering the standard extraction time in 1 h.  
For the extraction of EO from cathy leaves studied by [18], the plant material was subject to PEF with \(W_{s}\)= 20 kJ/kg, \(E=\) 4 kV/cm, and \(t_{dist}=\) 2 h. Differently from the results of the previous paper, the PEF pre-treatment resulted in an extraction yield deficit of 20%, when comparing to the control. Although the quantity of EO extracted differed negatively, the EO quality, analysed by CG, does not present significant changes. In relation to the extraction of EO from horehound researched by [19], PEF was applied with \(E=\) (0.8-2.5) kV/cm, N = 150, and 300, and \(t_{dist}\) of 30 and 60 min. The condition that maximizes the extraction yield is \(E=\) 2.5 kV/cm, N = 150 (minimum \(W_{s}\)), and \(t_{dist}=\) 30 min, whereas for the 60 min extraction, after PEF application, there is a significant yield shortage, \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Plant Material** & \(E\) (kV/cm) & \(W_{s}\) (kJ/kg) & **Number of Pulses** & \(T_{dist}\) (min) &
\begin{tabular}{c} **Average Yield** \\ **Increase (\%)** \\ \end{tabular} & **Ref.** \\ \hline Rosa alba L. & 4 & 10–20 & - & 30–150 & 13–33 & [7] \\ \hline Nepeta transcalcasci & 4 & 20 & - & 120 & \textless{}67 & [18] \\ \hline Marribiium volgar & 0.8–2.5 & - & 150–300 & 30–60 & 67–162 & [19] \\ \hline Flowers of Damask rose & 10–30 & - & 4–12 & 30–180 & 50 & [20] \\ \hline Artemisia herba alba & 1–3 & - & 100–300 & 30–60 & 150 & [21] \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Conditions and results of EO extraction yields, after PEF application, in the literature. even comparing to the control. The quality of the EOs extracted in this study was analysed through GC-MS, and the chemical composition did not change significantly. In relation to the extraction of EO from rose flowers investigated by [20], PEF was applied with \(E\) = 20 kV/cm and \(t_{dist}\) = 2 h. No influence on the quality of essential oils was observed, but there was an increase in methyl eugenol percentage, which is a disadvantage from a qualitative point of view. According to the results obtained, the treatment of rose flowers by PEF, before HD, can increase the yield by 50% and reduce the distillation to 120 min with 20 kV/cm. Finally, the extraction of EO from _Artemisia herba_ alba was investigated by [21], PEF was applied with 1, 2, and 3 kV/cm, with 100, 200, and 300 pulses, for HD times of 30 min and 60 min. The higher effect of PEF was achieved with 2 kV/cm, with 30 min HD and 200 pulses, an approximate 150% yield increase. For higher electric fields, the number of pulses, and 60 min HD the results got worse. According to our results, from the presented studies and experimental results reported by other authors, it is possible to conclude that the application of PEF to the plant materials previously to the distillation step manages to deliver higher EO extraction yields, and does not impact negatively on the EOs composition, when compared to the traditional methods. Nevertheless, it is possible to see, also, in the results reported by other authors some dispersion of the results, where standard deviations are shown, which hinders the conclusions. Hence, more investigation is needed.