## 3 Applications of Cold Atmospheric Pressure Plasma
### Food Industry and Agriculture
The low penetration depth of the plasma components is advantageous because more important nutrients can remain inside the food [10]. Spoilage of ready-to-eat salads (fruits and vegetables) due to microbial growth causes significant food waste. The effect of DBD plasma treatment on the quality (microbial load, hardness, pH value, color) and shelf life of fresh cut, leafy rocket salad was studied by [PERSON] et al. The greatest reduction of the load (_Pseudomonas_ spp.) was obtained after 10 min plasma treatment. The pH and color of the leaves were not affected, the shelf life was increased compared to untreated salad [101]. [PERSON] et al. used DBD plasma treatment for ready-to-eat ham to inactivate _Listeria monocytogenes_, which may occur during slicing and packing. They significantly reduced the cell counts (at least by 2 log) and studied the changes in color and lipid oxidation as a function of ham formulation, plasma treatment time, in-package gas composition and storage conditions [102]. Decontamination of food powders (e.g., onion powder, spices, black pepper, legume flour, milk powder) using plasma is more complex. Usually, it requires high plasma power density, long treatment time compared to flat samples. [PERSON] et al. published the inactivation efficiency of _Bacillus subtilis_ spores using an air surface microdischarge CAPP with low plasma power density (5 mW/cm\({}^{2}\)) and relatively short treatment time (7 min). The inhibiting effects on flat glass and corn starch samples were evaluated. Etching of spore hulls using reactive nitrogen species has been reported as a fundamental inactivation principle [103]. In the case of liquids, the penetration depth is less important, because every element comes into contact with the plasma volume, however, not only the pathogens are damaged [10]. Several studies confirmed that CAPP treatment has the ability to inactivate microorganisms (e.g., _Escherichia coli_ O157:H7, _Zygosaccharomyces rouxii, Salmonella enterica_) in fruit juices (e.g., apple, orange, blueberry) with very good inactivation rate. Although there is some uncertainty in the literature about the operating parameters and their effect on the quality parameters of the juices. Some researchers indicated that increasing treatment time can lead to color changes (ascorbic acid degradation), pH changes and changes in vitamin content (due to oxidation reactions). Moreover, additional research is needed for large scale processing and to prove that plasma does not have any toxic residuals [91]. Many different microorganisms attach to surfaces (e.g., food matrixes, processing equipment) and develop biofilms [57]. These complex microbial ecosystems are more resistant to various environmental stresses, antimicrobials and inactivation treatments (longer treatment time is necessary) than planktonic cells due to their three-dimensional extracellular matrix [25]. Biofilm inactivation process includes various processes, like destruction of extracellular matrix, cells and cell components, etching and reduction of biofilm thickness [57]. [PERSON] et al. also demonstrated that biofilms are less susceptible to cold plasma treatment. Furthermore, treatment efficiency depends on the biofilm age (mature biofilms are more resistant to CAPP than young biofilms) and the type of bacteria. They presented the inactivation of various single and mixed biofilm systems of _L. innocua_ and _E. coli_, which produced an extracellular polymeric substance matrix of different thickness and composition [92]. [PERSON] et al. extensively studied yeast cell inactivation at the subcellular level. It was shown that cold plasma may effectively lower the yeast cell physiological activities by the superposition of several mechanisms with different impacts (in particular, cell membrane damage, energy metabolism or DNA fragmentation).