# Study of the Effects of Plasma Pretreatment on the Microstructure of Peanuts
## 3 Results and Discussion
### Effects of Plasma on the Structure of Peanut Seed Coat
#### 3.1.2 Impact of Plasma Treatment Duration on the Structure of Peanut Seed Coat  
The results are presented in Figure 2. Figure 2c,d show the microstructures at 500\(\times\) and 2000\(\times\) magnifications, respectively, under SEM after treatment with helium gas (He) at 200 W for 30 s. Compared to the control group (Figure 2a), etching begins to appear on the seed coat surface with increased surface roughness, and the number of pores facilitating material exchange starts to increase. As the treatment duration increases, as shown in Figure 2c,e,g, cell boundaries become gradually clearer, arranged in tight order, with deeper and denser textures. The seed coat surface exhibits irregular concavities and protrusions. When magnified at 2000\(\times\) under SEM (Figure 2d,f,h), the pores for material exchange gradually transform into large cracks and holes with prolonged treatment, and the etching phenomenon intensifies significantly. The impact resembles that observed with increased plasma treatment power. With the continuous extension of plasma treatment time, the plasma continuously releases more reactive particles like reactive oxygen species (ROS), reactive nitrogen species (RNS), and high-energy electrons. These particles act on the seed coat surface for an extended period, gradually exposing and even breaking the surface fiber layer macromolecules, as seen in Figure 2j. The number of wrinkles and irregular fine scalp protrusions on the seed coat increases, with more pronounced white cracks indicating  
Figure 1: Appearance of peanuts under scanning electron microscope after treatment at different powers. Note: The left column shows SEM images at 500\(\times\) magnification. (**a**) Corresponds to the control group peanuts. (**c,e,g,i,k**) Correspond to peanuts treated with cold plasma at 100 W, 200 W, 300 W, 400 W, and 500 W for 60 s, respectively. The right column shows SEM images at 2000\(\times\) magnification. (**b**) Corresponds to the control group peanuts. (**d,f,h,j,l**) Correspond to peanuts treated with cold plasma at 100 W, 200 W, 300 W, 400 W, and 500 W for 60 s, respectively.  
breakage. When treatment time is extended to 150 s and the peanuts are viewed at 2000\(\times\) magnification under SEM (Figure 2l), small molecular protein bodies are observed to escape from the seed coat surface and to adhere freely above the seed coat.  
The reason for the above phenomenon may be that the peanut seed coat serves as a protective tissue, with its outermost layer being a cuticle composed primarily of fibrous compounds rich in flavonoids, polyphenols, and complex polysaccharides such as cellulose and hemicellulose. These substances play a crucial role in maintaining cell morphology and function [31; 32]. This may be attributed to the plasma treatment device releasing more high-energy electrons, ions, photons, and other particles. These particles undergo cross-linking reactions with macromolecules on the peanut seed coat surface, such as fibrous protein in the fiber structure, ultimately leading to this phenomenon. Improved hydrophilicity of peanuts, as observed by SEM, folds, and porosity on the surface increase water uptake and provide a simple transfer pathway for nutrient transfer to provide the energy required for germination and increased conductivity. Surface oxidizability is also associated with the degree of seed coat breakage, as found by [PERSON] et al. [33]. [PERSON] et al. [34] found that the relationship between the intensity of cold plasma treatment and protein function was not linear and that physical modifications via surface etching can control the treatment conditions and the number of proteins to obtain the desired modification results.  
Figure 2: _Cont._  
Figure 2: \(Cont.\)