# Study of the Effects of Plasma Pretreatment on the Microstructure of Peanuts
## 3 Results and Discussion
### Impact of Plasma Treatment on the Appearance and Structure of Peanut Embryos  
#### Impact of Plasma Treatment Power on the Appearance and Structure of Embryos  
The results are presented in Figure 4. Figure 4a,b are, respectively, the surface appearance images of peanut embryos in the control group at 500\(\times\) and 2000\(\times\) magnifications. At different magnifications, the peanut embryo surface exhibits a grid-like structure with slight undulations. Despite the irregularities, the surface appears clean and well-organized, with clear textures and micropores. Figure 4c,e,g show SEM images at 500\(\times\) magnification, corresponding to plasma treatment powers of 100 W, 200 W, and 300 W, respectively. Overall, the embryo surface remains smooth and structurally intact. However, cracks gradually increase, and lipid particles exude from the fissures, accumulating on the surface. The wrinkles become more pronounced and overlap and exposed protein particles are enveloped by the lipid bodies. This phenomenon is likely due to plasma etching. Figure 4i,k show SEM images at 500\(\times\) magnification, corresponding to plasma powers of 400 W and 500 W, respectively. Lipid bodies stack up, cracks increase and widen, and some cell structures rupture from cross-linked concavities. It is clearly observable that the higher the power, the greater the degree of destruction compared to the treatment group. Figure 4l shows the SEM image at 2000\(\times\) magnification. It reveals lipid particles migrating from the surface to the cracks, forming a mesh-like pattern. Protein aggregates disintegrate into smaller particles, possibly due to intense reactions between the released active species from ionization and surface macromolecules.  
The apparent phenomena observed in peanut seed embryos after plasma treatment could indicate that the peanut seed coat plays a certain protective role. The cell structure remains intact, with a single layer of epidermal cells and thin-walled cells forming the outer layer. Within the thin-walled cells, particles include lipid bodies, proteins, and starch granules. Peanut cell fat exists in the form of lipid bodies, and proteins are evenly dispersed within the fat [37]. As plasma treatment power increases, more high-energy active ions are released, enhancing penetration and exacerbating surface etching, leading to thin-walled cell wall rupture, allowing lipid particles to flow out through channels, covering exposed protein particles and starch granules. This phenomenon is evident in Figure 4g,i,k.  
Figure 3: Appearance of peanuts subjected to different treatment gases under a scanning electron microscope. Note: The left column shows SEM images at 500\(\times\) magnification. (**a**) Corresponds to the control group peanuts. (**c**,**e**,**g**) Correspond to peanuts treated with cold He, O\({}_{2}\), and Ar plasma, respectively, at 200 w for 60 s. The right column shows SEM images at 2000\(\times\) magnification. (**b**) Corresponds to the control group peanuts. (**d**,**f**,**h**) Correspond to peanuts treated with cold He, O\({}_{2}\), and Ar plasma, respectively, at 200 w for 60 s.  
Figure 4: _Cont._