# Novel Techniques for Microbiological Safety in Meat and Fish Industries
## 6 Non-Thermal Preservation Techniques  
### Cold Plasma  
Plasma is an ionized gas that contains atoms or molecules in a metastable state with a net electrical charge of approximately zero. Plasmas can be caused in any neutral gas by supplying enough energy to cause ionization of the gas [45]. Cold plasma is a source of high-energy electrons that interact in an open or controlled environment at ambient temperature and pressure [46]. When an electrical energy source is applied to a gas, many reactive species, such as ultraviolet photons, charged particles, radicals, and other reactive nitrogen, oxygen, and hydrogen species, are generated [47]. Cold plasma treatment is a successful food processing intervention for improved product protection and extended shelf life. Enabled cold plasma chemical species will quickly function at ambient temperatures against microorganisms without leaving any known chemical residue. In certain sites of a fungal cell, cold plasma species interact and result in a loss of function and structure and, eventually, cell death. The sun is a good example of thermal (hot) plasma at very high temperatures. A low-temperature plasma (cold) example is polar light [45]. Plasma ROS interacts harmfully with essential cell biomolecules, including DNA, proteins and cell enzymes. ROS can change biological membranes' function by interactions with lipids, causing the formation of unsaturated fatty acid peroxides in proteins and the oxidation of amino acids [48]. If the cell membrane of the bacterium is exposed to strong electric fields, it can be ruptured because of the electrostatic stress caused by the electrical charge that develops internally. Inactivation effects are subject to many factors, including plasma sources, operating conditions, gas used, the existence of the product/substratum and the microorganism itself [48]. Spoilage of raw meat is commonly associated with the growth of certain psychotropic bacteria, especially when the product is chilled and stored in aerobic conditions. The plasma jet, based on He+ O\({}_{2}\) DBD (dielectric barrier discharge), reduced the total bacteria count on chicken skin effectively and increased efficacy over time. _E. coli_ and _L. monocytogenes_ are the most resistant human pathogens in meat and meat products [48]. The use of an atmospheric plasma jet operating in He, He+O\({}_{2}\), N\({}_{2}\), or N\({}_{2}\)+O\({}_{2}\) to treat _L. monocytogenes_ inoculated on cooked chicken breast and ham was found to be successful in extending the shelf life of the products [49]. In meat and meat products, color and texture are essential physical qualities [48]. The treatment of pork and beef with flexible thin-layer DBD plasma with increased plasma treatment exposure time resulted in a reduction in redness [50]. Chicken breast treated with flexible DBD showed a reduction in redness and an improvement in lightness [51]. If myoglobin reacts with H\({}_{2}\)O\({}_{2}\) (hydrogen peroxide) to form choleglobin, meat discoloration can occur during plasma treatments [48]. In contrast to color, there are no discernible variations in texture between pork and beef loin. Similar scores for appearance, color, odor, and overall acceptability, but not taste, have been recorded in cooked pork and beef treated with DBD plasma when compared to the control [49]. In chicken breasts treated with flexible DBD, the production of some off flavors has been reported [51]. Cold plasma technology has been widely adopted to control the microbial growth of pathogens such as _Campylobacter jejuni_ by employing feed gases for 30 s to 180 s at a 5-12 mm distance from the plasma heat source that increased the surface temperature to 61 \({}^{\circ}\)C, resulting in a 1.42 CFU/cm\({}^{2}\) reduction [52]. Similarly to other technologies, the concept of hurdle technology is applied in the cold plasma method. In this method, atmospheric cold plasma has been applied with peracetic acid resulted in a significant reduction in _Salmonella_ load to a maximum of 5.3 log CFU/cm\({}^{2}\)[53].