_applied sciences_  
_Article_  
Reducing Storage Losses of Organic Apples by Plasma  
Processed Air (PPA)  
[PERSON] 1,*\({}^{\copyright}\), [PERSON] 1,*\({}^{\copyright}\), [PERSON] 2, [PERSON] 1, [PERSON] 1\({}^{\copyright}\) and [PERSON] 1\({}^{\copyright}\)  
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Footnote  
fruit and vegetables [16; 17; 18; 19]. Apples possess a protective cuticle and a natural wax surface, which makes the penetration of microorganisms more difficult. However, the fruit has gas exchange, which is guaranteed by lenticels [20]. Food spoilage is a complex process that can incorporate a variety of native and externally added microorganisms [21]. After damaging the upper layer, pathogenic bacteria like _Pectobacterium caroovorum_ can harm all parts of a plant [22; 23; 24]. Additionally, studies of [PERSON] et al. (2007) showed that the fungi _Penicillium expansum_, _Aspergillus niger_, _A. fumigatus_, _Alternaria tenuis_, _A. tenuissima_, _Cladosporium herbarum_, _Helmithosporium tetramers_, _Mucor racemosus_, _P. italicum_, and _Rhizopus nigricians_ were isolated from rotten apples [25]. This variety of apple-damaging microorganisms highlights the desire of many producers to have additional, more potent decontamination methods available. Against that background, non-thermal plasma at atmospheric pressure reveals a way to reduce storage losses [26; 27]. Physical plasmas contain excited gas molecules, positively and negatively charged ions, free electrons, reactive oxygen and nitrogen species (RONS), and various free radicals [28; 29; 30]. PPA is enriched with chemically reactive compounds such as the reactive nitrogenous and oxygen species (RONS) NO, NO\({}_{2}\), and H\({}_{2}\)O\({}_{2}\)[31; 32; 33; 34]. These reactive species can act antimicrobials by damaging DNA, disturbing the microbial signal transduction and impairing the cell envelope [35]. These compounds are thought to inhibit or prevent the growth of native microbial flora on food [36]. Inactivating microorganisms such as molds, bacteria or viruses can preserve apples longer. In general, in the field of biological decontamination, a wide range of plasma applications are currently being researched and applied in pilot projects [26; 37; 38]. The use of plasma-processed water (PTW) in decontamination processes is a promising way of its application, which showed huge reduction possibilities in terms of water and the use of chemicals [39; 40; 41].  
The main hypothesis of our work is an anti-microbiological effect of PPA on the microbial community found on apples. Thus, a PPA treatment extends the shelf life of the apples during storage in a cold atmosphere. Since lenticels possibly catch severe contamination, we focused on apple varieties that show well developed lenticels spreading uniformly on the apple surface [42]. The influences of PPA on the native microbial load were checked via a proliferation assay. To the best of our knowledge, the application of PPA and the up-scaled PPA process are novel for the sanitation of apples.  
The appearance of the apples was photographically observed, and the crispness of the apples after PPA treatment was detected with a texture analyzer.