# Non-Thermal Technologies in Food Processing: Implications for Food Quality and Rheology
## 6 Cold Plasma (CP)  
Cold plasma (CP) technology, a type of nonthermal plasma, has drawn a lot of interest in the food processing industry because of its potential for surface cleaning, microbiological inactivation, and shelf life extension while maintaining nutritional quality [164]. Electrons, ions, and radicals are among the active species that make up plasma, the fourth state of matter. According to their thermal equilibrium, the low-temperature plasma can be classified into cold plasma (nonthermal plasma) and quasi-equilibrium plasma (thermal plasma) [165]. Atmospheric cold plasma (ACP) is one of the most widely applied nonthermal plasma technologies that can be generated through various discharge methods, including corona discharge (CD), dielectric barrier discharge (DBD), micro-hollow-cathode discharge (MHCD), a plasma needle (PN), and an atmospheric pressure plasma jet [166; 167]. The initiation of CP results in numerous elastic and inelastic collisions between electrons, ions, and molecules [168]. Active components of CP, which are predominantly reactive oxygen species (ROS) and reactive nitrogen species (RNS), include the ozone, hydroxyl radicals, superoxide anions, nitric oxide, nitrogen dioxide, and nitrous oxide, and they play critical roles in food processing [169]. These ROS and RNS have strong oxidative properties and high diffusion coefficients, which enable them to diffuse efficiently and inactivate spoilage microorganisms on the surface of foods [167]. Their transient nature allows them to quickly recombine with molecules that have not reacted, returning the gas mixture to its initial state at the end of the treatment. As a result, CP is a residue-free and environmentally friendly technique that supports \"clean label\" processing principles [170]. In addition, since it can operate at an ambient temperature and pressure, it is particularly suitable for processing heat-sensitive foods while maintaining their quality and safety. Figure 5 illustrates how CP affects bacterial cell structures, leading to sterilisation and a loss of functionality. CP has been shown in recent studies to be successful in lowering bacterial infections in meat and dairy products without appreciably altering their nutritional value or sensory appeal. [PERSON] et al. [172] investigated the efficacy of cold plasma against _Salmonella enterica_ that has been injected on the surface of duck eggshells. In this context, arc plasma was applied to _Salmonella_-contaminated duck eggs for 10, 20, 30, and 40 s. The findings showed that the _Salmonella_ population was considerably reduced by all plasma treatments, and that the bactericidal effects of plasma were strengthened by longer treatment durations. After 40 s of plasma application, a maximum bacterial decrease of a 4.1 log cycle was noted. Additionally, egg quality measures, such as the eggshell strength, eggshell colour, and yolk colour, were unaffected by the plasma treatments [172]. Furthermore, the use of CP technology to inactivate food-borne pathogens in the fresh-cut fruit and vegetable sector has been assessed, considering the several drawbacks to using chlorine and other chemical agents for microbial inactivation in the industry, such as residue retention and inefficiency due to dilution and degradation over time [170]. [PERSON] et al. [173] assessed the efficacy of high-voltage ACP in reducing the natural microflora of carrots treated for 1, 2, 3, 4, and  
Figure 5: A schematic of the action of cold plasma on bacterial cell structures resulting in loss of functionality and sterilisation [171]. 5 min at 60, 80, and 100 kV (60 Hz frequency). Carrot discs treated at 100 kV for 5 min (\(\sim\)250 W power) showed a population reduction of about 2 log10 CFU/g in both yeast and mould and total aerobic mesophiles. Only slight changes in the pH, colour, texture, and total carotenoids were observed in the CP-treated carrots, proving CP to be a better treatment option than chlorine, hydrogen peroxide, and high-pressure carbon treatment.