# Enhancement of Wheat Flour and Dough Properties by Non-Thermal Plasma Treatment of Wheat Flour
## 1 Introduction
Corona discharge (CD) and dielectric barrier discharge (DBD) are two forms of atmospheric non-thermal plasmas that can produce abundant amounts of ozone together with some other active species [34]. In contrast to ozone generators, DBD and CD can produce ozone in situ and create a ground for a direct reaction between reactive oxygen species and wheat proteins. Plasma is a an overall neutral gas, mainly composed of positively and negatively charged particles, neutrons, ions and particles that are heavy and with high energies [35]. Plasma is the fourth state of matter and is abundantly present in the universe. It was first discovered in the 18 th century by [PERSON] and named by [PERSON] and [PERSON] in 1929 [36]. Based on electron temperature and thermodynamic equilibrium, plasma can be classified as high-temperature (thermal) or low-temperature (non-thermal) plasma [37]. Ionization degree may vary from partial ionization, in the case of NTP, to full ionization, in the case of thermal plasma [38]. Thermal plasmas with high electron densities (>10\({}^{22}\) m\({}^{-3}\)) and temperatures (4000 to 20,000 K) can be produced by electric discharge to reach high current flow through a fully ionized gas [39]. Electron temperature in NTP is much higher compared to the temperature of the bulk gas molecules, leading to a much lower temperature of the overall plasma, in the range of 30-50 \({}^{\circ}\)C [7]. NTP is thus quite suitable for the treatment of living cells, tissues and heat-sensitive materials [38]. Numerous researchers ([4; 40; 41; 42; 43; 44; 45]) have studied the interaction of DBD plasma with wheat flour and have found that ozone and active species (H\({}^{\bullet}\), O\({}^{\bullet}\), OH\({}^{\bullet}\), HO\({}_{2}\)\({}^{\bullet}\)) generated during gas ionization can promote structural changes in starch and protein macromolecules (e.g., promoting cross-linking, depolymerization between molecules and the formation of new functional groups) similar to the changes induced by the use of chemicals. [PERSON] et al. [46] studied the influence of NTP treatment on wheat flour structural properties and determined an increase in the elastic and viscous modulus of the prepared dough. Modifications to biological characteristics and surface properties were confirmed by [PERSON] et al. [34]. They reported no change in the total aerobic bacterial count and non-starch lipids. No visible change in the total protein amount was reported; however, there was a trend towards higher-molecular weight fractions, which resulted in thicker dough. NTP, which is produced in a gas phase, is rich in high-energy species and the contact between the surfaces of flour particles and plasma species is crucial for its structural changes. The reactor design for flour treatment with NTP is of vital importance, as it influences the uniform exposure to plasma species and thus allows for optimal effects of plasma treatment in terms of flour functionality [47]. This study introduces a novel concept of a cylindrical, rotational reactor for wheat flour treatment with in situ produced NTP. Ease of scaling up was considered as a key factor during the development of the concept. The research focus was on defining the optimal operating conditions (e.g., the minimal treatment time) to reach the maximum dough strength, as well as understanding the influence of reactor capacity and the influence of environmental air temperature change (often variable from day to day) on the efficiency of the NTP treatment process.