# Enhancement of Wheat Flour and Dough Properties by Non-Thermal Plasma Treatment of Wheat Flour
## 3 Results and Discussion
### Effects of Environmental Temperature during NTP Treatment on Dough Properties  
Further, the effect of environmental air temperature on the NTP treatment of flour was investigated. A lower voltage demand for plasma formation and an earlier air breakdown due to increased air temperature was reported in the literature [76; 77; 78].  
A flour sample (type 550, mass 50 g) was treated in the rotational reactor. The air temperature in the plasma reactor chamber was increased using an air heater in 10 \({}^{\circ}\)C steps from 10 \({}^{\circ}\)C to 40 \({}^{\circ}\)C while keeping the relative humidity at 50% \(\pm\) 10%. The experimental results, shown in Figure 9, demonstrate the dependence of the visco-elastic properties of wheat dough produced at various air temperatures on the non-thermal plasma treatment. Statistical analysis (ANOVA) confirmed the existence of significant statistical differences between the untreated and treated samples, with _p_-values obtained less than 0.05. Independent of air temperature, the results demonstrated an increase in the visco-elastic properties of the dough produced with NTP-treated flour.  
The results presented in Table 3 demonstrate the change (in percentage) in visco-elastic properties (G\({}^{\prime}\) and G\({}^{\prime\prime}\)) of wheat doughs produced with plasma-treated flour samples at air temperatures between 10 \({}^{\circ}\)C and 40 \({}^{\circ}\)C in comparison to the control sample. When  
Figure 9: Change in the storage (G\({}^{\prime}\)) and loss (G\({}^{\prime\prime}\)) moduli of wheat dough as a function of environmental (air) temperature.  
NTP was generated at an air temperature up to 20 \({}^{\circ}\)C, the visco-elastic properties of dough increased maximally between 25 and 53%. When the air temperature increased to 30 \({}^{\circ}\)C, the change in visco-elastic properties almost doubled. A further increase in air temperature (i.e., 40 \({}^{\circ}\)C) did not further affect the values of visco-elastic properties significantly.  
The breakdown voltage demand is strongly influenced by the gas temperature, as it is inversely proportional to the temperature of the gas, as shown in Equation (5) [78]:  
\[\mathrm{U}=(\mathrm{T}_{\mathrm{r}}/\mathrm{T}_{\mathrm{g}})\times\mathrm{U} _{\mathrm{o}} \tag{5}\]  
where U (V) and U\({}_{\mathrm{o}}\) (V) are the breakdown voltage at the desired gas temperature and gas breakdown voltage at room temperature, respectively; T\({}_{\mathrm{r}}\) is the ambient room temperature (300 K); and T\({}_{\mathrm{g}}\) is the gas temperature.  
If the temperature of the gas is increased, the breakdown voltage demand decreases and vice versa. It has been reported that air warmed to a certain temperature impairs its insulating power and makes it dielectrically weak, resulting in the formation of the arc at longer distances [79]. This means that if the discharge gap and supply voltage is constant (as is the case here; i.e., if a 2 mm discharge gap and a constant maximum voltage of 7 kV is supplied to the system), then at lower temperatures (in this case, an air temperature of 10 \({}^{\circ}\)C) the gas is partially ionized, leading to the production of a limited number of active species. This limit is overruled by the increase in the gas temperature (in this case, 30 \({}^{\circ}\)C), as at that constant voltage and discharge gap, the gas is more easily ionized (decrease in air dielectric strength) due to higher temperatures. Further increase in temperature leads to a decrease in breakdown voltage demand; however, the number of active species stays constant, as the gas is already fully ionized at lower temperatures. This was the reason why a strong increase in visco-elastic properties in wheat flour was noticed as the air temperature was increased from 10 \({}^{\circ}\)C to 30 \({}^{\circ}\)C. However, no further increase in visco-elastic properties was detected when the air temperature was increased to 40 \({}^{\circ}\)C.