## 3 Results and Discussion
### Bacterial Inactivation Effect and Kinetics Model Analysis
#### 3.1.1 Effect of Solid Surface on Inactivation of _S. typhimurium_ and _S. aureus_ by DBD-NTP
\begin{table}
\begin{tabular}{l c c c c c c c c} \hline  & **Population** & \multicolumn{2}{c}{**log \(N_{0}\) (log (CFU/mL)/**/**} & & & & \\  & & **log \(N_{0}\) (log (CFU/cm2))** & \(K_{\rm max}\) & \(t_{\rm I}\) & \multicolumn{2}{c}{**log \(N_{\rm rms}\) (log (CFU/cm2))**} & \multicolumn{2}{c}{**\(D\) value 1**} & \multicolumn{2}{c}{**Log Reduction**} & \multicolumn{1}{c}{**RMSE 2**} \\  & & **log \(N_{0}\) (log (CFU/cm2))** & \(K_{\rm max}\) & \(t_{\rm I}\) & \multicolumn{2}{c}{**log \(N_{\rm rms}\) (log (CFU/cm2))**} & \multicolumn{2}{c}{**2**} & \multicolumn{1}{c}{**RMSE 3**} & \multicolumn{1}{c}{**R 2**} \\ \hline NaCl 0.9\% & Total & 7.91 \(\pm\) 0.10\({}^{\rm\,\alpha\rm{AB}}\) & 0.26 \(\pm\) 0.011\({}^{\rm\,\alpha\rm{AB}}\) & 73.3 \(\pm\) 4.08\({}^{\rm\,\alpha\rm{C}}\) & 81.71 \(\pm\) 3.72\({}^{\rm\,\alpha\rm{C}}\) & 8.07 \(\pm\) 0.10\({}^{\rm\,\alpha\rm{A}}\) & 0.4002 & 0.9895 \\  & Uninjured & 7.76 \(\pm\) 0.15\({}^{\rm\,\alpha\rm{C}}\) & 0.22 \(\pm\) 0.007\({}^{\rm\,\alpha\rm{D}}\) & 63.8 \(\pm\) 1.08\({}^{\rm\,\alpha\rm{C}}\) & 73.6 \(\pm\) 0.78\({}^{\rm\,\alpha\rm{D}}\) & 8.09 \(\pm\) 0.07\({}^{\rm\,\alpha\rm{A}}\) & 0.4519 & 0.9876 \\ NaCl 12\% & Total & 7.76 \(\pm\) 0.15\({}^{\rm\,\alpha\rm{C}}\) & 0.34 \(\pm\) 0.011\({}^{\rm\,\alpha\rm{A}}\) & 50.2 \(\pm\) 1.15\({}^{\rm\,\alpha\rm{D}}\) & 56.62 \(\pm\) 0.94\({}^{\rm\,\alpha\rm{D}}\) & 8.09 \(\pm\) 0.07\({}^{\rm\,\alpha\rm{A}}\) & 0.6705 & 0.9815 \\  & Uninjured & 7.64 \(\pm\) 0.16\({}^{\rm\,\alpha\rm{C}}\) & 0.32 \(\pm\) 0.015\({}^{\rm\,\alpha\rm{A}}\) & 48.2 \(\pm\) 1.93\({}^{\rm\,\alpha\rm{D}}\) & 55.02\({}^{\rm\,\alpha\rm{I}}\) & 8.08 \(\pm\) 0.09\({}^{\rm\,\alpha\rm{A}}\) & 0.7184 & 0.9783 \\ PBS pH = 6.0 & Total & 7.93 \(\pm\) 0.14\({}^{\rm\,\alpha\rm{AB}}\) & 0.21 \(\pm\) 0.041\({}^{\rm\,\alpha\rm{C}}\) & 72.5 \(\pm\) 1.42\({}^{\rm\,\alpha\rm{C}}\) & 8.32 \(\pm\) 1.63\({}^{\rm\,\alpha\rm{C}}\) & 6.57 \(\pm\) 1.23\({}^{\rm\,\alpha\rm{B}}\) & 0.1618 & 0.9968 \\  & Uninjured & 7.82 \(\pm\) 0.15\({}^{\rm\,\alpha\rm{C}}\) & 0.20 \(\pm\) 0.031\({}^{\rm\,\alpha\rm{C}}\) & 67.8 \(\pm\) 3.31\({}^{\rm\,\alpha\rm{C}}\) & 78.84 \(\pm\) 2.97\({}^{\rm\,\alpha\rm{D}}\) & 6.83 \(\pm\) 0.99\({}^{\rm\,\alpha\rm{D}}\) & 0.2185 &As shown in Tables 1 and 2, \(D\) values for _S. typhimurium_ and _S. aureus_ on the surface of glass slides were 9.14 s and 9.11 s, respectively, and on the surface of gelatin plates were 23.66 s and 25.47 s, respectively. These results indicated that bacteria on the gelling plates were much harder to kill by DBD-NTP than bacteria loaded on glass slides. The differences between glass slides and gelatin plates could be due to the amount of water and chemical composition of medium effect [27]. [PERSON] et al. [27] reported that charged particles generated in plasma catalyzed peroxidation of lipids and polysaccharides on the cell membranes, with reaction rate described above. Bacteria loaded on surface of slides are covered with layer of water molecules bound by van der Waals forces, whereas bacteria loaded on gelatin are covered with thick layer of free water. Charged particles catalyze oxidation and erosion processes of both surface and interior of microorganisms and presence of water and reactive species play a synergistically effect role which contribute to faster inactivation. Cell seems to be less susceptible and slopes of survival curves became flatter at the latter half of inactivation process. Plasma acts only on the surface and charged particle and reactive species cannot penetrate deep into the substrates. It seems plausible that dead bacteria on top layers could form a physical protective layer covering the surviving bacteria. Meanwhile, disruption of membrane integrity could lead to the release of highly oxidative materials (e.g., membrane lipids, free fatty acids, etc.) [28]. The oxidizable materials could serve as a \"quenching\" phase for the highly reactive, oxidizing species produced by plasma, thereby resulting in a decline in microbial inactivation.