## 3 Results  
### Inactivation Effect of 365 and 395 nm LED Treatment  
In low-a\({}_{\mathrm{w}}\)_S_. Typhimurium \(m\) prepared with a longer drying and equilibration period, the viable cell counts were reduced from 12.55 \(\pm\) 0.614 log (CFU/mL) to 10.99 \(\pm\) 0.473 log (CFU/g) after the drying and equilibration steps used in Section 2.1. The treatment with 365 nm light pulses with 28.9 (10 min) and 188.1 (60 min) J/cm\({}^{2}\) doses showed a reduction of 0.37 \(\pm\) 0.119 and 1.44 \(\pm\) 0.039 log (CFU/g) in \(S\). Typhimurium cell counts in low-a\({}_{\mathrm{w}}\) conditions, respectively. In addition, the treatment with 395 nm light pulses with 138.8 (10 min) and 834.4 (60 min) J/cm\({}^{2}\) doses resulted in reductions of 1.88 \(\pm\) 0.069 and 2.88 \(\pm\) 0.397 log (CFU/g) in the low-a\({}_{\mathrm{w}}\)_S_. Typhimurium cell counts, respectively (Table 1). In the case of low-a\({}_{\mathrm{w}}\)_S_. Typhimurium prepared with a shorter drying and equilibration period, the drying and equilibration steps produced no effect on the viable cell counts of the \(S\). Typhimurium cells (Figure 1). The inactivation efficacy of the 365 and 395 nm light pulses was evaluated by treatment of 10 mg of low-a\({}_{\mathrm{w}}\)_S_. Typhimurium with \(\sim\)217 J/cm\({}^{2}\) dose at 4 cm from the LED head and at 80% power level. Overall, the antibacterial effect of the 365 nm LED treatments against low-a\({}_{\mathrm{w}}\)_S_. Typhimurium was higher than 395 nm LED treatment with same dose (\(p\) < 0.0001). For example, 365 nm light pulses produced a reduction of 2.94 \(\pm\) 0.339 log (CFU/g) as compared with 1.08 \(\pm\) 0.073 log (CFU/g) by 395 nm light pulses in low-a\({}_{\mathrm{w}}\)_S_. Typhimurium cell counts with the \(\sim\)217 J/cm\({}^{2}\) dose treatment (Figure 1). \begin{table}
\begin{tabular}{c c c c} \hline  & **Treatment Time** & **Treatment Dose** & **Log (CFU/g)** \\  & **(min)** & **(J/cm\({}^{2}\))** & **Log (CFU/g)** \\ \hline Inoculum before drying & - & - & \(12.55\pm 0.614\)\({}^{\mathrm{a}}\) (in Log CFU/mL) \\ After drying & - & - & \(10.99\pm 0.473\)\({}^{\mathrm{b}}\) \\ Control (after equilibration to & 0 & 0.000 & \(10.73\pm 0.483\)\({}^{\mathrm{b}}\) \\
0.75 a\({}_{\mathrm{w}}\)) & 10 & 28.9 & \(10.36\pm 0.054\)\({}^{\mathrm{b}}\) \\
365 nm & 60 & 188.1 & \(9.29\pm 0.127\)\({}^{\mathrm{c}}\) \\
395 nm & 10 & 138.8 & \(8.85\pm 0.479\)\({}^{\mathrm{c}}\) \\  & 60 & 834.4 & \(7.85\pm 0.462\)\({}^{\mathrm{d}}\) \\ \hline \end{tabular} The results are represented as means \(\pm\) standard deviation of three independent replicates. Values with different superscripts in each column differ significantly (\(p\) < 0.05).  
\end{table} 
Table 1: Effect of 365 and 395 nm LED treatment on the survival of \(S\). Typhimurium ATCC13311 cells, dried and equilibrated to 0.75 a\({}_{\mathrm{w}}\). Treatments with the 365 and 395 nm light pulses of low-a\({}_{\mathrm{w}}\)_S_. Typhimurium cells were performed for 10 and 60 min corresponding to treatment doses of 28.9 and 188.1 J/cm\({}^{2}\) for 365 nm and 138.8 and 834.4 J/cm\({}^{2}\) for 395 nm, respectively, at 60% power level and at 4 cm from the LED heads. The high-intensity light pulses increased the surface temperature of the low-\(\rm{a_{w}}\) bacteria (\(p\) = 0.0008). The 395 nm LED produced a higher increase in the surface temperature of the low-\(\rm{a_{w}}\)\(S\). Typhimuriumium as compared with the 365 nm LED treatments with the same dose (\(p\) = 0.0036) (Table 2). Although the surface temperature was increased to only \(\rm{-43~{}^{o}C}\), this might play a role in the inactivation efficacy of the 395 nm LED. The LED treatments also reduced the weight of the treated low-\(\rm{a_{w}}\)\(S\). Typhimuriumium (\(p\) < 0.0001), and the weight loss could be attributed to the drying by the 365 and 395 nm LED treatments.